musculo skeletal radiology
TRANSCRIPT
-
8/6/2019 Musculo Skeletal Radiology
1/57
Editors: Brant, William E.; Helms, Clyde A.
Title: Fundamentals of Diagnostic Radiology, 3rd Edition
Copyright 2007 Lippincott Will iams & Wilkins
> Table of Contents > Section X - Musculoskeletal Radiology > Chapter 41 - Benign Cystic
Bone Lesions
Chapter 41
Benign Cystic Bone Lesions
Clyde A. Helms
A benign, bubbly, cystic lesion of bone is one of the more common skeletal
lesions that a radiologist encounters. The differential diagnosis can be quitelengthy and is usually structured on how the lesion looks to the radiologist, usinghis or her experience as a guide. This method, called pattern identification,certainly has merit, but it can lead to a very long differential diagnosis and manyerroneous conclusions if not tempered with some logic.
In general, if a differential diagnosis wil l yield the correct diagnosis 95% of thetime, most would consider it a useful differential l ist; however, it would not be
appropriate to accept a 1-in-20 miss rate for fractures and dislocations. Ingeneral, the shorter the differential diagnosis l ist, the more helpful it is toclinicians and the easier it is to remember. A shorter differential l ist wil l usuallyhave a lower accuracy rate than a long list; however, many times the longer l ists
contain such rare entities that the accuracy does not really increasesubstantially. For most of the entities in bone radiology, a 95% accurate
differential is acceptable. If one wants to be more accurate than that, morediagnoses can simply be added to the l ist of differential possibil ities.
When the differential diagnosis is long, as in the differential for bubbly, cystic
lesions of bone, it can be difficult to recall all of the entities that should bementioned. A mnemonic can be helpful in recall ing long lists of information and
is recommended.
FEGNOMASHICFEGNOMASHICis a mnemonic that serves as a nice starting point for discussingpossibil ities that appear as benign, cystic lesions in bone. This mnemonic has
been in general use for many years. By itself, it is merely a long list14entitiesand it needs to be coupled with other criteria to shorten the l ist into amanageable form for each particular case. For instance, the age of the patient
will help add or eliminate many of the possibil ities. If multiple lesions arepresent, only half a dozen entities n eed to be discussed. Methods of narrowingthe differential are discussed later in this chapter.
The first step in approaching a benign, cystic bone lesion is to be certain it isreally benign. The criteria for differentiating benign lesions from malignant
Page 1 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
2/57
lesions are covered in Chapter 42. Once it is established that the lesion is truly abenign, cystic lesion, FEGNOMASHIC will enable a differential diagnosis that is at
least 95% accurate. Memorization of the 14 entities in this differential is easilydone (Table 41.1).
The next step after learning the names of all of the lesions is getting some idea
of each lesion's radiographic appearance. This is when experience becomes a
factor. For the medical student or first-year resident, it is difficult to go beyondsaying that they all look cystic, bubbly, and benign. The fourth-year residentshould have no trouble
differentiating between a unicameral bone cyst and a giant cell tumor because he
or she has seen examples of each many times before and knows theirappearance.
P.1064
TABLE 41.1 Discriminators for Benign Lytic Bone
LesionsMnemonic: FEGNOMASHIC
Letter Represents Characteristics
F Fibrous dysplasia No periosteal reaction
E Enchondroma 1. Calcification present (exceptin phalanges)
2. Pain less (no per iost i tis)
Eosinophi li c g ranu loma Younger than age 30
G Giant cel l tumor 1. Epiphyses closed2. Abuts the art icular surface (in
long bones)3. Wel l def ined w ith a
nonsclerotic margin (in longbones)
4. E ccen tri c
N Nonossifying fibroma 1. Younger than age 30
2. Pain less (no per iost i tis)3. Corti ca ll y based
O Osteoblastoma Mentioned when aneurysmal bone
Page 2 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
3/57
After getting a feel for what each lesion looks l ike radiographically andovercoming the frustration that builds when one realizes that many of them look
alike, one should try to learn ways to differentiate each lesion from the others. Ihave developed a number of keys that I call discriminators, which help to
differentiate each lesion. These discriminators are 90% to 95% useful (I willmention when they are more or less accurate, in my experience) and are by nomeans intended to be absolutes or dogma. They are guidelines but have a highaccuracy rate.
Textbooks rarely state that a finding always o r never occurs. Theytemper descriptions with virtually always, invariably,usually, or characteristically. I have tried to pick out findings thatcome as close to always as I can, realizing that I wil l only beapproximately 95% accurate. That is good enough for most radiologists.
The following is only a brief description of each entity; more completedescriptions are readily available in any skel etal radiology text. What isemphasized here are the points that are unique for each entity, thereby enabling
cyst (ABC) is mentioned (especially
in the posterior elements of thespine)
M Metastatic diseasesand myeloma
Older than age 40
A Aneurysmal bone cyst 1. Expansile2. Younger than age 30
S Solitary bone cyst 1. Central
2. Younger than age 30
H Hyperparathyroidism(brown tumor)
Must have other evidence ofhyperparathyroidism
I Infection Always mention
C Chondroblastoma 1. Younger than age 302. Epiphyseal
Chondromyxoid No calcified matrix
Page 3 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
4/57
differentiation from the others. Table 41.1 is a synopsis of these discriminators.
Fibrous DysplasiaFibrous dysplasia is a benign congenital process that can be seen in a patientof any age and can look like almost any pathologic process radiographically. It
can be wild looking, discretely lucent, patchy, sclerotic, expansile, multiple, and
many other descriptions. It is, therefore, difficult to look at a bubbly lytic lesionand unequivocally say it is or is not fibrous dysplasia. It would be better if theFEGNOMASHIC differential started on a positive note, say, with giant cell tumor
or chondroblastoma, for which there are some definite criteria. However, becausefibrous dysplasia is first on the l ist, we might as well deal with it.
How do you know whether to include or excl ude fibrous dysplasia if it can looklike almost anything? Experience is the best guideline. In other words, look in a
few texts and find as many different examples as possible; get a feeling for whatfibrous dysplasia looks l ike.
Fibrous dysplasia wil l not have periostitis associated with it; therefore, if
periostitis is present, one may safely exclude fibrous dysplasia. Fibrous dysplasia
FIGURE 41.1. Fibrous Dysplasia. This patient has polyostotic fibrous
dysplasia with diffuse involvement of the pelvis as well as the proximalfemurs.
P.1065
Page 4 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
5/57
virtually never undergoes malignant degeneration and should not be a painfullesion unless there is a fracture. An occult fracture often occurs in long bones
with fibrous dysplasia; therefore, it is not unusual to have it present with painand no obvious fracture seen in a long bone. Pain in a flat bone, such as the ribs
or pelvis (nonweight-bearing bones), should not occur with fibrous dysplasia.
Fibrous dysplasia can be either monostotic (most commonly) or polyostotic and
has a predilection for the pelvis, proximal femur, ribs, and skull. When it ispresent in the pelvis, i t is invariably present in the ipsilateral proximal femur(Figs. 41.1, 41.2). I have seen only one case in which the pelvis w as involved
with fibrous dysplasia, and the proximal femur was spared. The proximal femur,however, may be affected alone, without involvement in the pelvis (Fig. 41.3).
Fibrous dysplasia often involves the ribs. It typically has an expansile, lyticappearance in the posterior ribs (Fig. 41.4) and a sclerotic appearance in the
anterior ribs.
The classic description of fibrous dysplasia is that it has a ground-glass or smokymatrix. This description confuses people as often as it helps them, and I do not
recommend using ground-glass appearance as a buzz word for fibrousdysplasia. Fibrous dysplasia is often purely lytic and becomes hazy or takes on a
ground-glass look as the matrix
calcifies (Fig. 41.5). It can go on to calcify significantly, and then it presents asa sclerotic lesion. Also, I often see lytic lesions with a pathologic diagnosis other
than fibrous dysplasia that have a distinct ground-glass appearance; therefore,the ground-glass qualifier can be misleading.
P.1066
Page 5 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
6/57
FIGURE 41 . . Fibrous Dysplasia. This patient has polyostotic fibrousdysplasia with involvement of the right femur as well as the supraacetabular
portion of the ilium. When the pelvis is involved with fibrous dysplasia, the
ipsilateral femur on the affected side is invariably also involved.
Page 6 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
7/57
FIGURE 41.3. Fibrous Dysplasia. This patient has a well-defined lytic
lesion with a hazy, ground-glass appearance in the neck of the right femur.
The pelvis was uninvolved. It is not unusual for monostotic fibrous dysplasiato involve the proximal femur and spare the pelvis.
Page 7 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
8/57
FIGURE 41.4. Fibrous Dysplasia. When fibrous dysplasia affects the ribs,
the posterior ribs often demonstrate a lytic expansile appearance, as in this
example. When the anterior ribs are involved, they are most often sclerotic
in appearance. Note also the involvement of the thoracic spine.
Page 8 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
9/57
AdamantinomaWhen a lesion i s encountered in the tibia that resembles fibrous dysplasia, an
adamantinoma should also be considered. An adamantinoma is a malignanttumor that radiographically and histologically resembles fibrous dysplasia (Fig.
41.6). It occurs almost exclusively in the tibia and the jaw (for unknown
reasons) and is rare. Because it is rare, one may choose not to include it in the
differentiala misdiagnosis will not occur more than once or twice in a lifetime.
McCune Albrig t SyndromePolyostotic fibrous dysplasia occasionally occurs in association with caf-au-lait
FIGURE 41 . . Fibrous Dysplasia. Polyostotic fibrous dysplasia is seen in
the radius in this child. Parts of this lesion have a hazy, ground-glass
appearance, whereas others are more l ytic appearing. A hazy, ground-glass
appearance is often present in fibrous dysplasia, but just as often, the
appearance can be purely lytic or even sclerotic.
Page 9 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
10/57
spots on the skin (dark-pigmented, frecklelike lesions) and precocious puberty.
This complex is called McCune-Albright syndrome. The bony lesions in this
syndrome, and even in the simple polyostotic form, often occur
unilaterallythat is, throughout one half of the body. This
does not happen often enough to be of any diagnostic use in differentiating
fibrous dysplasia from other lesions.
The presence of multiple lesions of fibrous dysplasia in the jaw has been termed
c er ism This is from the physical appearance of the child with puffed-out
cheeks having an angelic look. The jaw lesions of cherubism regress in
P.1067
FIGURE 41 . . Adamantinoma. This mixed lytic and sclerotic process in the
midshaft of the tibia is characteristic for fibrous dysplasia. An
adamantinoma has an identical appearance and should be considered in any
tibial lesion that resembles fibrous dysplasia. Biopsy showed this to be an
adamantinoma.
Page 10 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
11/57
adulthood.
Discriminator
No periosteal reaction.
Enchondroma and Eosinophilic GranulomaEnchondromas occur in any bone formed from cartilage and may be central,
eccentric, expansile, or nonexpansile. They invariably contain calcified chondroid
matrix, except when in the phalanges. An enchondroma is the most common
benign cystic lesion in the phalanges (Fig. 41.7). If a cystic lesion is present
without calcified chondroid matrix anywhere except in the phalanges, I do not
include enchondroma in my differential.
Often it is difficult to differentiate between an enchondroma and a bone infarct.
An infarct usually has a well-defined, densely sclerotic, serpiginous border (Fig.
41.8), whereas an enchondroma does not (Fig. 41.9). An enchondroma often
causes endosteal scalloping, whereas a bone infarct will not. Although these
criteria are helpful in separating an infarct from an enchondroma, they are not
foolproof.
Page 11 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
12/57
It is difficult, if not impossible, to differentiate an enchondroma from a
chondrosarcoma. Clinical findings (primarily pain) serve as a better indicatorthan radiographic findings, and indeed pain in an apparent enchondroma should
warrant surgical investigation. Periostitis should not be seen in an enchondroma
either. Trying to differentiate histologically an enchondroma from a
chondrosarcoma is also difficult, if not impossible, at times. Biopsy of an
apparent enchondroma should not be performed routinely for histologic
differentiation.
Multiple enchondromas occur on occasion; this condition has been termed
FIGURE 41 . . Enc ondroma. A lytic lesion in the phalanges is most
commonly an enchondroma. This is the only location in the skeleton where
an enchondroma does not contain calcified chondroid matrix. These most
often present with pathologic fractures, as in this example.
Page 12 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
13/57
Ollier disease (Fig. 41.10). It is not
hereditary and does not have an increased rate of malignant degeneration. The
presence of multiple enchondromas associated with soft tissue hemangiomas is
known as Maffucci syndrome (Fig. 41.11). This syndrome also is not hereditary;
however, it does have an increased incidence of malignant degeneration of theenchondromas.
P.1068
P.1069
FIGURE 41 . . Bone Infarct. These lytic lesions in the distal femurs with
calcified, serpiginous borders are typical for bone infarcts. Occasionally, the
differential between a bone infarct and an enchondroma can be difficult on
plain films; however, in this example, infarcts are easily diagnosed.
Page 13 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
14/57
FIGURE 41 . . Enc ondroma. This lesion in the distal right femur shows
the stippled, punctate calcification typical for chondroid matrix seen in an
enchondroma.
Page 14 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
15/57
FIGURE 41.1 . Ollier Disease. Multiple enchondromas are present
throughout the hand. This is a typical example of Ollier disease.
Page 15 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
16/57
Discriminators1. Must have calcification (except in phalanges). 2. No periostitis or pain.
Eosinophilic granuloma (EG) is a form of histiocytosis X, the other forms being
Letterer-Siwe disease and Hand-Schller-Christian disease. Although theseforms may be merely different phases of the same disease, most investigators
categorize them separately. The bony manifestations of all three disorders are
similar and are discussed in this review simply as EG.
Unfortunately for radiologists, EG has many appearances (1). It can be lytic or
sclerotic, it may be well defined or ill defined, it might or might not have a
sclerotic border, and it might or might not elicit a periosteal response. The
periostitis, when present, is typically benign in appearance (thick, uniform,
FIGURE 41.11. Maffucci Syndrome. Multiple enchondromas associatedwith phleboliths are present in the phalanges. This combination of findings
invariably represents hemangiomas and enchondromas in Maffucci
syndrome.
Page 16 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
17/57
wavy) but can be lamellated or amorphous. EG can mimic Ewing sarcoma and
present as a permeative (multiple small holes) lesion.
How, then, can one distinguish EG from any of the other lytic lesions in this
differential? Remember that it is difficult to exclude EG from almost any
differential of a bony lesion, be it benign or malignant. EG occurs almost
exclusively in patients under 30 years (usually
-
8/6/2019 Musculo Skeletal Radiology
18/57
EG might or might not have a soft tissue mass associated, so the presence or
absence of a soft tissue mass will not help in the differential diagnosis. I know of
no entity in which the presence or absence of an associated soft tissue mass will
warrant inclusion or exclusion of the process from a differential. It is important
to note the presence of a soft tissue mass (or its absence), but this will do little
to narrow the differential diagnosis.
Most radiologists are inept at evaluating the soft t issues because they aredifficult to see, and CT and MR have made
it unnecessary in most cases to rely on plain films alone for the soft tissues.
Fortunately, in most cases, the presence or absence of a soft tissue mass will not
alter the differential diagnosis. The treating physician will undoubtedly want to
know whether the soft tissues are involved and to what extent; this can be
satisfactorily demonstrated with MR.
P.1070
Page 18 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
19/57
EG occasionally has a bony sequestrum (Fig. 41.14). Only a few other entities
have been described that on occasion have bony sequestra: osteomyelitis,
lymphoma, and fibrosarcoma; therefore, when a sequestrum is identified, EG,
osteomyelitis, lymphoma, and fibrosarcoma should be considered. As discussed
in Chapter 47, an osteoid osteoma will often give an appearance of a
sequestration when the nidus is partially calcified. Clinically, EG might or might
not be associated with pain; therefore, clinical history is noncontributory for the
most part.
DiscriminatorMust be under age 30 years.
Giant Cell umor
FIGURE 41.13. Eosinop i lic G ranuloma EG . Well-defined lytic lesions
are present throughout the pelvis in this 24-year-old patient. In addition tothe lesion around the right hip, a lesion is seen a t the right sacroiliac joint.
Biopsy showed this to be EG.
Page 19 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
20/57
Giant cell tumor is an uncommon, somewhat controversial lesion with several
schools of thought as to its radiographic appearance. I subscribe to the most
widely used approach, as do the majority of radiologists and pathologists (2).
First, it is important to realize that one is unable to tell whether a giant cell
tumor is benign or malignant, regardless of its radiographic appearance.
Histologically, a giant cell tumor cannot be divided into either a benign or a
malignant category. Most surgeons curettage and pack the lesions and consider
them benign unless they recur. Even then, they can still be benign and recur a
second or third time. About 15% of giant cell tumors are thought to be malignant
on the basis of their recurrence rate. When malignant, they can metastasize to
the lungs, but they do so infrequently.
Four classic radiographic criteria for diagnosing giant cell tumors exist. If any of
these criteria are not met when looking at a lesion, giant cell tumor can beeliminated from the differential diagnosis.
1. Giant cell tumor occurs only in patients with closed epiphyses; this is valid
at least 98% to 99% of the time and is extremely useful. I do not entertain
the diagnosis of giant cell tumor in a patient with open epiphyses.
2. The lesion must be epiphyseal and abut the articular surface (Fig. 41.15).
FIGURE 41.14. Eosinop i lic G ranuloma EG . This well-defined lytic
lesion contains a bony sequestrum (arro ), which is typical for osteomyelitis
or EG. Biopsy revealed this to be EG.
Page 20 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
21/57
There is disagreement as to whether giant cell tumors begin in the
epiphyses or metaphyses or from the physeal plate itself; however, except
for rare cases, when radiologists see the lesions, they are epiphyseal and
are flush against the articular surface. The metaphysis also has some of the
tumor in it because the lesions are generally very large. When one sees a
giant cell tumor, it will be epiphyseal. Perhaps more importantly, it should
be flush against the articular surface of the joint. This occurs in 98% to99% of giant cell tumors; therefore, if I have a lesion that is
separated from the articular surface by a definite margin of normal bone, I
will not include giant cell tumor in the diagnosis. This rule does not apply in
flat bones, such as i n the pelvis or in the apophyses (Fig. 41.16), which
have no articular surfaces.
P.1071
FIGURE 41.1 . Giant Cell Tumor. A well-defined lytic lesion without
a sclerotic margin is seen abutting the articular surface of the distal
femur in a patient who has closed epiphyses. These are all
Page 21 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
22/57
3. Giant cell tumors are said to be eccentrically located in the bone, as
opposed to being centrally placed in the medullary cavity. When a bonylesion is quite large, it can be difficult to tell whether it is central or
eccentric. I do not find this to be a terribly useful description, but it is one
of the classic rules of a giant cell tumor.
4. The lesion must have a sharply def ined zone of transition (border) that is
not sclerotic. This is a very helpful finding in giant cell tumor. The only
places this does not apply is in flat bones, such as the pelvis (Fig. 41.17)
and the calcaneus.
It is important to realize that the four criteria for a giant cell tumor apply only to
giant cell tumors and not to any other lesion. For instance, I know of no other
lesion that depends on whether the epiphyses are open or closed. No other lesion
in any of my lists uses as a diagnostic factor whether the zone of transition is
sclerotic or not (many lesions, such as nonossifying fibromas, will usually have a
sclerotic margin, but it does not occur often enough to include as a
discriminator). No other lesion must always abut the articular surface, and no
other lesion has the classic
description of being eccentrically placed (although several lesions, including
nonossifying fibroma and chondromyxoid fibroma, are eccentric most of the
time).
characteristics of a giant cell tumor.
P.1072
Page 22 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
23/57
FIGURE 41.1 . Giant Cell Tumor. This well-defined lytic lesion that does
not have a sclerotic margin completely involves the greater trochanter. The
apophyses have the same differential diagnosis as lesions in the epiphyses,
which makes giant cell tumor a strong possibility in this example. Biopsy
showed this to be a giant cell tumor.
Page 23 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
24/57
FIGURE 41.1 . Giant Cell Tumor. A large, well-defined lytic lesion in the
iliac wing is seen, which does contain a sclerotic margin and does not
appear to abut any articular surface. The pelvis is a good location for giant
cell tumor, which this proved to be at biopsy. The usual rules for giant cell
tumors such as presence of a nonsclerotic margin do not apply in flat bones.
FIGURE 41.1 . Fibrous Cortical Defect. A well-defined lytic lesion is seen
in the medial metaphysis of this tibia (arro s), which is typical for a fibrous
cortical defect.
Page 24 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
25/57
FIGURE 41.1 . Nonossifying Fibroma. A large, well-defined lytic lesion,
which is slightly expansile with scalloped sclerotic margins, is seen in the
distal tibia in this young patient. This is a characteristic appearance of a
nonossifying fibroma. The examination was obtained for a sprained an kle
and not for this asymptomatic lesion.
Page 25 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
26/57
Although these four criteria apply well for giant cell tumor, they do not apply at
all for any other lesions. Residents have a tendency to apply these criteria to
every lytic lesion encountered for the simple reason that they have learned the
four criteria.
Once one of the criteria is violated, the remainder do not even have to be used
to eliminate a giant cell t umor. For instance, if a lytic lesion is found in the mid-
diaphysis of a bone, giant cell tumor can be excluded. There is no need to check
further to see whether it is eccentric, whether it has a nonsclerotic margin, or
FIGURE 41. . Nonossifying Fibroma. A well-defined, expansile lytic
lesion in the distal f ibula is noted in this asymptomatic patient, which is
characteristic for a nonossifying fibroma.
Page 26 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
27/57
whether the epiphyses are closed.
Again, these rules will be greater than 95% effective and, in my experience,
close to 99% effective. It should be noted that these criteria only apply to giant
cell tumors of long bones. They would not work, for instance, in the pelvis or the
calcaneus, two locations where giant cel l tumors often occur. If one or two cases
are found that do not fit the criteria, another pathologist should review the
slides.
Many pathologists refer to aneurysmal bone cysts as giant cell tumors; hence,
they have giant cell tumors that do not obey any of the criteria. These
pathologists may be correct, but they are not in the mainstream of what most
people use for giant cell tumor criteria, both radiographically and histologically.
Discriminators1. Epiphyses must be closed. 2. Must abut the articular surface. 3. Must be well
defined with a nonsclerotic margin. 4. Must be eccentric.
onossifying Fibroma onossifying f ibroma (NOF) is probably the most common bone lesion
encountered by radiologists. It reportedly occurs in up to 20% of children and
usually spontaneously regresses, so as to be seen only rarely after the age of
30. Fibrous cortical defect is a c ommon synonym, although some people
differentiate the two lesions on the basis of size, with a fibrous cortical defect
being smaller than 2 cm in length (Fig. 41.18) and an NOF being larger than 2
cm (Fig. 41.19). Histologically, these lesions are identical; therefore, it seems
appropriate to refer to them all as NOFs rather than to subdivide them by their
size.
P.1073
Page 27 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
28/57
NOFs are benign, asymptomatic lesions that typically occur in the metaphysis of
a long bone, emanating from the cortex. They classically have a thin, sclerotic
border that is scalloped and slightly expansile (Fig. 41.20); however, this is a
general description that probably applies to o nly 75% of the lesions and could
equally apply to most of the lesions in FEGNOMASHIC. They do not have to haveexpansion or a scalloped or sclerotic border and are not limited to the
metaphyses. Then how are they best recognized? The best way is to familiarize
oneself with their general appearance by looking at examples in textbooks. That
can be done in 15 minutes. It is important to recognize these lesions because
they are what I call dont touch lesions (see Chapter 46); that is, the
radiologist's diagnosis should be the final word and thereby supplant a biopsy.
These lesions are so characteristic that no differential diagnosis should be
FIGURE 41. 1 . Nonossifying Fibroma. A. A well-defined, lytic lesion that
is minimally expansile is seen in the distal ti bia in this child who was
examined for a sprained ankle. B. A CT examination showed apparentcortical destruction (arro ), which was believed to be suggestive of an
aggressive lesion. Biopsy showed this to be a nonossifying fibroma. Both CT
and MR will often show apparent cortical destruction, which is merely
cortical replacement by benign fibrous tissue.
Page 28 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
29/57
entertained, although a few entities can indeed occasionally simulate them.
If a CT or MR is obtained of an NOF, there will often appear to be interruption of
the cortex, which can be misinterpreted as cortical destruction (Fig. 41.21). This
merely represents cortical replacement by benign fibrous tissue and should not
warrant further investigation.
P.1074
FIGURE 41. . Healing Nonossifying Fibroma. A predominantly sclerotic
lesion, which is minimally expansile and well defined, is seen in the proximal
humerus in this child who is asymptomatic. This is a typical appearance of a
disappearing or healing nonossifying fibroma. With time, this l esion will meltinto the normal bone and essentially disappear.
Page 29 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
30/57
FIGURE 41. 3 . Nonossifying Fibroma. This large, well-defined lytic lesion
with faint sclerotic margins is seen in the distal femur. It has a very typical
appearance for a giant cell tumor; however, it has sclerotic margins and
does not abut the arti cular surface. The lesion underwent biopsy and was
found to be a n onossifying fibroma.
Page 30 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
31/57
If the patient is older than 30 years of age, NOF should not be included in the
differential diagnosis. NOFs must be as ymptomatic and exhibit no periostitis,
unless there is an antecedent history of trauma. They routinely heal with
sclerosis and eventually disappear (Fig. 41.22), usually around the ages of 20 to
30 years. During this healing period, they can appear hot on a radionuclide bone
scan because there is osteoblastic activity. These lesions can occasionally get
quite large (Fig. 41.23); therefore, growth or change in size should not alter the
diagnosis. They are most commonly seen about the knee but can occur in any
long bone. Occasionally, multiple NOFs are seen about the knee, each of which is
characteristic in appearance.
Discriminators1. Must be younger than age 30 years. 2. No periostitis or pain. 3. Cortically
based.
steoblastoma s teoblastomas are rare lesions that co uld justif iably be excluded from this
differential without the fear of missing a diagnosis more than once in a lifetime.
Why, then, include them? The mnemonic FEGNOMASHIC would not have nearly
the same ring without the extra vowel, so osteoblastoma remains.
Osteoblastomas have two appearances: (1) They look like large osteoid osteomas
and are often called i ant osteoid osteomas Because osteoid osteomas are
FIGURE 41. 4 . Osteoblastoma. A. A lytic expansile lesion involving the
right T12 pedicle (arro ) and transverse process is seen on thisanteroposterior plain film. B. The lesion is seen on CT to extend into the
vertebral body. It has intact cortices and contains some calcif ied matrix.
This is a classic example of an osteoblastoma of the spine.
P.1075
Page 31 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
32/57
sclerotic lesions and do not resemble bubbly lytic lesions, this is not the type of
osteoblastoma we are concerned with in this differential. (2) They simulate
aneurysmal bone cysts (ABCs). They are expansile, often having a soap-
bubble appearance. If an ABC is being considered, so should an
osteoblastoma. Osteoblastomas commonly occur in the posterior elements of the
vertebral bodies, and about half of the cases demonstrate speckled calcif ications
(Fig. 41.24). A classic radiology differential is that of an expansile lytic lesion ofthe posterior elements of the spine, which includes osteoblastoma, ABC, and
tuberculosis.
DiscriminatorMentioned when ABC is mentioned (especially in the posterior elements of the
spine).
Metastatic Disease and MyelomaMetastatic disease should be considered for any lytic lesionbenign or
aggressive in appearancein a patient over 40 years of age. Metastatic diseasecan appear perfectly benign radiographically (Fig. 41.25), so it i s not valid to
say, Because this lesion looks benign, it should not be a metastasis. Most
metastatic disease has an aggressive appearance and will not be in the
FEGNOMASHIC differential, but a significant number of metastases appear
benign. In fact, metastases can have any radiographic appearance; therefore,
any bone lesion in a patient older than the age of 40 should have metastatic
disease as a consideration, unless trauma or arthritis is the primary concern.
Page 32 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
33/57
For statistical purposes, I do not mention metastatic disease in a pati ent younger
than age 40. I will be correct more than 99% of the time using 40 as a cutoff
age. Otherwise, metastatic diseases would have to be mentioned in every single
case of a lytic lesion, and I prefer to limit the list of differential possibilities. I
am not claiming that met astatic disease does not occur in patients younger thanage 40only that I consider it acceptable to miss it (unless given a history of a
known primary neoplasm).
MyelomaAlthough myeloma most commonly presents as a diffuse permeative process in
the skeleton (Fig. 41.26), it can present as either a solitary lesion (Fig. 41.27)
or as multiple lytic lesions. Bubbly, lytic bone lesions of myeloma are more
FIGURE 41. . Metastatic Disease. A well-defined lytic lesion is seen inthe proximal femur in this 50-year-old patient who had pain associated with
this lesion. Biopsy showed this to be a renal metastasis. A significant
number of metastatic lesions can have a completely benign appearance, as
in this example.
Page 33 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
34/57
correctly called p a smac t omas I mention plasmacytoma separately from
metastatic disease because it can occur in a slightly younger population (age
greater than 35 years is my cutoff) and can precede clinical or hematologic
evidence of myeloma by 3 to 5 years. In general, there is no harm in lumping all
metastatic disease, including myeloma, into one group and using greater than
age 40 as the limiting factor.
Virtually any metastatic process can present as a lytic, benign-appearing lesion;
therefore, it serves no purpose to
try to guess the source of the metastatic disease from its appearance. In
general, lytic expansile metastatic diseases tend to come from thyroid and renal
tumors (Fig. 41.28). The only metastatic lesion that is said to always be lytic is
renal cell carcinoma.
Discriminator
Must be older than age 40 years.
P.1076
FIGURE 41. . Multiple Myeloma. A. A diffuse permeative pattern is
present throughout the femur in this patient wit h multiple myeloma. B. A
lateral skull f ilm shows a typical presentation of multiple myeloma in the
skull with multiple small holes throughout the calvaria, which are well
defined.
Page 34 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
35/57
FIGURE 41. . l asmacytoma. A large, well-defined lytic lesion is seen in
the left ilium (arro s) in this patient with multiple myeloma. This is a
common location for a plasmacytoma. Like metastases, plasmacytomas often
have a completely benign appearance.
Page 35 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
36/57
neurysmal one Cyst neurysmal bone cysts (ABCs) are the only lesions I know of that are named
for their radiographic appearance. They are virtually always aneurysmal or
expansile (Figs. 41.29, 41.30). Rarely, an ABC will present before it is expansile,
but that is unusual enough not to worry about. Aneurysmal bone cysts occur
primarily in patients who are younger than age 30, although occasionally one will
be encountered in older patients. I use bony expansion and age of less than 30
years as fairly rigid guidelines and seldom miss the diagnosis of ABC. They often
have fluidfluid levels on CT or MR (Fig. 41.31), although this is a nonspecific
FIGURE 41. . Metastatic Disease. An expansile lesion with a soap-
bubble appearance is present in the proximal radius in a patient with renal
cell carcinoma. An expansile lytic lesion is a common finding with renal or
thyroid metastatic disease.
P.1077
Page 36 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
37/57
f inding, as many other lesions can have fluidfluid levels.
ABCs are, like giant cell tumors, somewhat controversial. There are apparently
two types of ABCs: a primary type and a secondary type. The secondary type
occurs in conjunction with another lesion or from trauma, whereas a primary ABC
has no known cause or association with other lesions. Secondary ABCs have been
said to occur with giant cell tumors, osteosarcomas, and almost any other lesion.
I have seen dozens of ABCs and have seen only a few in association with another
lesion. As to occurring after trauma, I do not understand why they would be age-
limited if trauma were causative. Also, malignant tumors
were once thought to occur after trauma because of the frequent association of a
history of antecedent trauma with malignant bone tumors. This is not seriously
considered today and is thought to be coincidental. I suspect that ABCs and
trauma are also coincidental, but this is mere speculation.
P.1078
FIGURE 41. . Aneurysmal Bone Cyst. An expansile lytic lesion is present
in the distal femur in this 24-year-old patient who presents with pain. This
is a fairly typical appearance for an aneurysmal bone cyst.
Page 37 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
38/57
FIGURE 41.3 . Aneurysmal Bone Cyst. A well-defined expansile lesion is
seen in the midshaft of the ulna in a child who presented with pain in this
region. This is a characteristic appearance for an aneurysmal bone cyst.
Page 38 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
39/57
ABCs typically present because of pain. They can occur anywhere in the skeleton,
and there is no location that would make them more highly ranked in the
differential diagnosis. As with osteoblastoma, they often o ccur in the posteriorelements of the spine.
FIGURE 41.31. Aneurysmal Bone Cyst. An axial T2WI through a thoracic
vertebral body shows an expansile lesion involving the posterior elements
that has several fluidfluid levels (arro s). This is a typical appearance
for an aneurysmal bone cyst.
Page 39 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
40/57
FIGURE 41.3 . Solitary Bone Cyst. A well-defined lytic lesion is present in
the proximal humerus in this child who suffered a fracture through the
lesion. The location and central appearance, as well as the age of the
patient, are characteristic for a solitary bone cyst. A piece of cortical bone
has broken off and descended through the serous fluid contained within the
lesion and can be seen in the dependent portion of the lesion (arro ) as a
fallen fragment sign. A fallen fragment sign is said to be pathognomonic for
a unicameral bone cyst.
Page 40 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
41/57
Discriminators1. Must be expansile. 2. Must be younger than age 30 years.
olitary one Cyst o li tary bone cysts are also called simp e one c sts or nicamera one c sts
They are not necessarily unicameral (one compartment), however. This is the
only lesion in FEGNOMASHIC that is always central in location. Many of the other
lesions may be central, but a solitary bone cyst can be excluded if it is not. It is
one of the few lesions that does not occur most commonly around the knees. Two
thirds to three fourths of these lesions occur in the proximal humerus (Fig.
41.32) and proximal femur (Fig. 41.33). Application of this rule alone is not that
helpful, or one third to one fourth of lesions would be missed.
Solitary bone cysts are usually asymptomatic unless fractured, which is a
common occurrence. Even when pathologic fractures occur, they rarely form
periostitis. A classic radiographic finding for a solitary bone cyst is the fallen
fragment sign (see Fig. 41.32). This occurs when a piece of cortex breaks offafter a fracture in a so litary bone cyst, and the piece of cortical bone sinks to
the gravity-dependent portion of the lesion. This has not been
described in any other lesion and indicates a fluid-filled cystic lesion, rather than
a lesion fi l led with m atrix.
P.1079
Page 41 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
42/57
FIGURE 41.33. Solitary Bone Cyst. A well-defined lytic lesion, which is
central in location, is seen in the proximal femur in this child. This is
characteristic for a solitary bone cyst.
Page 42 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
43/57
FIGURE 41.34. Solitary Bone Cyst. A well-defined lytic lesion is seen in
the calcaneus abutting the inferior surface, which is typical in location and
appearance for a solitary bone cyst. A solitary bone cyst in the calcaneus
occurs almost exclusively in this location and is not subject to pathologic
fracture as readily as when one occurs in the proximal femur and humerus.
Page 43 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
44/57
Solitary bone cysts occur almost exclusively in young patients (under age 30).
Although long bones are most commonly involved, solitary bone cysts have been
described in almost every bone in the body. They begin at the physeal plate in
long bones and grow into the shaft of the bone; therefore, they are not
epiphyseal lesions. They can, however, extend up into an epiphysis after the
plate closes, but this is unusual. A fairly common location is in the calcaneus,
where they have a characteristic location adjacent to the inferior surface of the
calcaneus (Fig. 41.34).
Discriminators1. Must be central. 2. Must be younger than age 30 years. 3. No periostitis.
yperparathyroidism ro n umors ro n tumors of hyperparathyroidism (HPT) can have almost any appearance,
from a purely lytic lesion (Fig. 41.35) to a sclerotic process. Generally, when the
patient's HPT is treated, the brown tumor undergoes sclerosis and will eventually
disappear. If a brown tumor is going to be considered in the differential
diagnosis, additional radiographic findings of HPT should be seen. Subperiosteal
bone resorption is pathognomonic for HPT and should be
searched for in the phalanges (particularly in the radial aspect of the middle
phalanges) (Fig. 41.35), distal clavicles (resorption), medial aspect of the
proximal tibias, and sacroiliac joints. If the physes are open, they should have a
frayed, ragged appearance, as in rickets, owing to the effect of parathormone.
Osteoporosis or osteosclerosis might suggest that renal osteodystrophy with
secondary HPT is present, but subperiosteal resorption must be present, or
brown tumor can be safely excluded from the differential.
FIGURE 41.3 . Bro n Tum or. A. An expansile lytic lesion is seen in the
fifth metacarpal (arro s), and a second, smaller lytic lesion is seen in the
proximal portion of the fourth proximal phalanx. B. This patient is noted to
have subperiosteal bone resorption, best seen in the radial aspect of the
middle phalanges (arro s) as indistinct, interrupted cortex. This makes the
diagnosis of hyperparathyroidism with multiple brown tumors most likely.
P.1080
Page 44 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
45/57
Most authorities believe that brown tumors occur most commonly in primary
HPT; however, because we see so many more patients with secondary HPT, more
brown tumors are seen in patients with secondary rather than primary HPT.
DiscriminatorMust have other evidence of HPT.
Infection
InfectionUnfortunately, there is no reliable way radiographically to exclude a focus of
osteomyelitis. It has a protean radiographic appearance and can occur at any
location and in a patient of any age. It might or might not be expansile, have a
sclerotic or nonsclerotic border, or have associated periostitis (3). Therefore,
infection will be in almost every differential diagnosis of a lytic lesion, which is
acceptable, as it is one of the most common lesions encountered. Soft tissue
findings such as obliteration of adjacent fat planes are notoriously unreliable and
even misleading, because tumors and EG can do the same thing.
When osteomyelitis occurs near a joint, if the articular surface is abutted,
invariably the joint will be involved and show cartilage loss, an effusion (Fig.
FIGURE 41.3 . Osteomyelitis. A. A plain film of the proximal humerus in
this child with shoulder pain reveals a well-defined lytic lesion in the medial
metaphysis. B. T2WI of the humerus shows the lesion to have high signal
and an associated joint effusion. The probable site of connection to the joint
can be seen (arro ), which likely represents a draining abscess. Aspiration
of the joint fluid revealed pus. This is a large focus of osteomyelitis or
Brodie abscess.
Page 45 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
46/57
-
8/6/2019 Musculo Skeletal Radiology
47/57
FIGURE 41.3 . Osteomyelitis. A. A lytic lesion is present in the proximal
humerus, which has some associated periostitis laterally. B. CT scan through
this area reveals a lytic lesion that contains a calcific density within (arro ),
which is a bony sequestrum. This is an area of osteomyelitis with a bony
sequestration.
Page 47 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
48/57
The differential diagnosis of a lytic lesion in the epiphysis of a patient under 30
years of age is simple: (1) infection (most common), (2) chondroblastoma, and
(3) giant cell tumor (which has its own diagnostic criteria, so it can usually be
definitely ruled out or in). This is an old, classic differential and probably
encompasses 98% of epiphyseal lesions.
A caveat on epiphyseal lesions is to always consider the possibility of a
subchondral cyst or geode (Fig. 41.39), which has been described in four disease
processes: (1) degenerative joint disease (must have joint space narrowing,
sclerosis, and osteophytes); (2) rheumatoid arthritis; (3) calcium pyrophosphate
dihydrate crystal disposition disease or pseudogout; and (4) avascular necrosis.
The clinician must be certain no joint pathology that might indicate one of these
processes is present, or an unnecessary biopsy of a geode might be performed
on the basis of the differential of an epiphyseal lesion.
Apophyses are identical to epiphyses as far as the differential diagnosis of lytic
lesions, with the exception of geodes, which only occur adjacent to articular
surfaces. The carpal bones, the tarsal bones, and the patella have
FIGURE 41.3 . C ondroblastoma. A plain film in this young patient shows
a well-defined lytic lesion in the greater tuberosity of the humerus. Biopsy
showed this to be a chondroblastoma.
Page 48 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
49/57
a tendency to behave like epiphyses in their differential diagnosis of lesions.
Therefore, a lytic lesion in these areas has a similar differential diagnosis as an
epiphyseal lesion.
Discriminator1. Must be younger than age 30. 2. Must be epiphyseal.
Chondromy oid FibromaChondromy oid fibroma, like osteoblastoma, is such a rare lesion that failure
to mention it is probably not going to result in missing more than one in a
lifetime. Why include it, then? I recommend not including it, but it is part of the
classic FEGNOMASHIC differential. If it is mentioned, at least know what it looks
like. Basically, chondromyxoid fibromas resemble NOFs. Unlike NOFs, however,
they can be seen in a patient of any age. Chondromyxoid fibromas often extend
P.1082
FIGURE 41.3 . Geode. A large, well-defined lytic lesion in the proximal
humerus is present, which is associated with marked degenerative disease
of the glenohumeral joint. When definite degenerative joint disease is
present and associated with a lytic lesion, the lytic lesion should be
considered to be a geode. A biopsy was performed, which confirmed this to
be a geode, or subchondral cyst; however, the biopsy could have been
avoided.
Page 49 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
50/57
into the epiphyses (Fig. 41.40), whereas NOFs rarely do. Also, they can present
with pain, which will not occur with an NOF. They have been reported to progress
from a benign process to an aggressive and even malignant lesion, but this is
extremely rare. Although chondromyxoid fibromas are cartilaginous lesions,
calcified cartilage matrix is virtually never seen radiographically.
Discriminator1. Mention when an NOF is mentioned. 2. No calcified matrix.
FIGURE 41.4 . C ondromy o id F ib roma. A well-defined lytic lesion in the
distal tibia that extends slightly into the epiphysis is noted on thisanteroposterior plain film. A nonossifying fibroma could certainly have this
appearance; however, this underwent biopsy and was found to be a
chondromyxoid fibroma. Chondromyxoid fibromas often extend into the
epiphysis, as in this example, whereas nonossifying fibromas usually do not.
Page 50 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
51/57
S MMA That, in essence, is the differential diagnosis for a benign cystic lesion of bone.
It is probably 98% accurate, which is good enough for most radiologists. To
increase the accuracy to 99%, it would be necessary to add many uncommon or
rare lesions, and the whole process would become too confusing for most
radiologists to learn and
apply. If there is a favorite lesion that is not on this list, by all means add it.
Likewise, if the list is already too cumbersome, forget about osteoblastoma and
chondromyxoid fibroma. I am unable to make it much simpler than that and still
be reasonably accurate.
P.1083
TABLE 41. Lesions in atients ounger T an ears of Age
Eosinophilic granuloma
Aneurysmal bone cyst
Nonossifying fibroma
Chondroblastoma
Solitary bone cyst
Page 51 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
52/57
Some of the l esions I have purposefully omitted are intraosseous ganglion,
pseudotumor of hemophilia, hemangioendothelioma, ossifying fibroma,
intraosseous lipoma, glomus tumor, neurofibroma, plasma cell granuloma, and
schwannoma. Others could be added to this list, of course, but are best left to
the pathologistnot the radiologistfor the diagnosis.
There are several features that are somewhat useful in separating the various
lesions in FEGNOMASHIC. For instance, if the patient is younger than the age of
30 years, be sure to consider EG c ondro astoma NOF so itar one c st , and
A C (Table 41.2). If the patient is over 30 years of age, those five lesions can be
excluded. Note that this is not a differential diagnosis for lesions in patients
under age 30; it simply means these entities should not be mentioned in older
patients. For those younger than age 30, other lesions such as fibrous dysplasia
and infection must also be mentioned.
There are a few lytic lesions that have no good discriminators other than age
and, therefore, must be mentioned routinely. I call these lesions
automatics because one should automatically mention them regardless of
the location or appearance of the lesion. Infection and EG must be mentioned for
those younger than age 30, whereas metastatic disease and infection must be
included in any differential in a patient older than age 40 (Table 41.3). These
lesions have a protean radiographic appearance and should be mentioned not
only in the benign cystic differential but also for an aggressive lesion.
TABLE 41. Automatics
Younger than age 30
InfectionEosinophilic granuloma
Older than age 40
Infection
Metastatic disease and myeloma
TABLE 41.4 Lesions T at Ha e No ain or eriostitis
Page 52 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
53/57
If periostitis or pain is present (assuming no trauma, which can be a foolhardy
assumption), you can exclude fi ro s d sp asia so itar one c st NOF , and
enc ondroma (Table 41.4). If the lesion i s epiphyseal, the differential is
infection iant ce t mor c ondro astoma (and do not forget eodes) (Table
41.5). If the patient is over 40 years of age, add metastatic disease and
m e oma and remove c ondro astoma from the epiphyseal list.
The epiphyseal differential tends to apply also to the tarsal bones (especially the
calcaneus), the carpal bones, and the patella. In the calcaneus, a unicameral
bone cyst should also be considered and has a characteristic appearance and
location (see Fig. 41.34). Apophyses are epiphyseal equivalents and have
the same differential as epiphyses. The difference between an epiphysis and an
apophysis is that epiphyses contribute to the length of a bone, whereas
apophyses serve as ligamentous attachments.
Fibrous dysplasia
Enchondroma
Nonossifying fibroma
Solitary bone cyst
TABLE 41. Epip yseal Lesions
Infection
Giant cell tumor
Chondroblastoma
Geode
Page 53 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
54/57
A classic differential for benign, cystic rib lesions is the mnemonic FAME, in
which F = f i ro s d sp asia, A = A C , M = metastatic diseases and m e oma,
and E enc ondroma and EG (Table 41.6). If multiple lytic l esions are present,
FEEMHI is a useful mnemonic of the lesions in FEGNOMASHIC that can be
multiple: F = fi ro s d sp asia, E enc ondroma, E EG, M = metastatic
disease and m e oma, H perparat roidism (brown tumor), and I i nfection
(Table 41.7).
A few findings that just do not seem to narrow the differential diagnosis are
presence or absence of a s oft tissue mass, expansion of the bone (except it must
be present in an A BC), sclerotic or nonsclerotic border (except it must be
nonsclerotic in giant cell tumor), presence or absence of bony struts or
compartments in the lesion, and size of the lesion.
If calcif ied matrix is identified in a lesion, it is tempting to narrow the
differential to either the osteoid series
or the chondroid series of lesions, depending on the character of the matrix. Be
careful of this. Very few radiologists can reliably differentiate chondroid fromosteoid matrix. Routine calcif ication of a lesion or debris, detritus, or
sequestrations in osteomyelitis can mimic ch ondroid or osteoid calcif ication and
be misleading. The only lesion that must exhibit calcif ied matrix is the
enchondroma (except in the phalanges). Chondroblastomas and osteoblastomas
demonstrate calcif ied matrix about half the time, and chondromyxoid fibromas
never have radiographically demonstrable calcif ied matrix.
P.1084
TABLE 41. Differential for ib Lesions
Fibrous dysplasia
Aneurysmal bone cyst
Metastatic disease and myeloma
Enchondroma and eosinophilic granuloma
TABLE 41. Multiple Lesions FEEMHI
Page 54 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
55/57
DIFFE ENTIAL DIAGNOSIS OF A SCLE OTIC
LESIONMany lytic lesions spontaneously regress and are not usually seen in patients
over 30 years of age. When these lesions regress, they often fill in with new
bone and have a sclerotic or blastic appearance. Therefore, when a sclerotic
focus is identified in a 20- to 40-year-old patient, especially if it is an
asymptomatic, incidental finding, the
following lesions should be considered: NOF (Fig. 41.41), EG, aneurysmal bone
cyst, solitary bone cyst, and chondroblastoma. Several other lesions should be
included that can also a ppear sclerotic: fibrous dysplasia, osteoid osteoma,
infection, brown tumor (healing), and perhaps a giant bone i sland (Fig. 41.42).
In any patient older than the age of 40 years, the number one possibility shouldbe metastatic disease.
Fibrous dysplasia
Eosinophilic granuloma
Enchondroma
Metastatic disease and myeloma
Hyperparathyroidism (brown tumors)Infection
P.1085
Page 55 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
56/57
FIGURE 41.41. Healing Nonossifying Fibroma. A plain film of the knee in
this 25-year-old patient reveals a sclerotic lesion in the proximal tibia,
which is a healing or resolving nonossifying fibroma.
Page 56 of 57Ovid: Fundamentals of Diagnostic Radiology
5/23/2011mk:@MSITStore:M:\medicalheaven_radiology2\Fundamentals%20of%20Diagnostic%20...
-
8/6/2019 Musculo Skeletal Radiology
57/57
EFE ENCES
1. David R, Oria R, Kumar R, et al. Radiologic features of eosinophilic
granuloma of bone. Pictorial essay. AJR Am J Roentgenol 1989;153:
10211026.
2. Dahlin D. Giant cell tumor of bone: highlights of 407 cases. AJR Am J
Roentgenol 1985;144:955960.
3. Gold R, Hawkins R, Katz R. Pictorial essay. Bacterial osteomyelitis:
findings on plain radiography, CT, MR, and scintigraphy. AJR Am J
Roentgenol 1991;157:365370.
FIGURE 41.4 . Giant Bone Island. A large sclerotic lesion is present in
the right supraacetabular region of the ilium (arro ), which represents a
giant bone island. The sli ghtly feathered margins of the trabeculae, which
blend in with the normal bone, and the long axis of the lesion being in the
direction of primary weight bearing are characteristic for a bone island.
Page 57 of 57Ovid: Fundamentals of Diagnostic Radiology