Pathology of the Soft Tissues & Nerves

Arlene L. Santos, M.D.SY 10-11

Pathology of the Soft Tissues

I. Fatty Tumors

II. Fibrous Tumors & Tumor-like Lesions

III. Fibrohistiocytic Tumors

IV. Tumors of the Skeletal Muscle

V. Tumors of the Smooth Muscle

VI. Tumors of the Skeletal Muscle

I. Fatty Tumors

A. Lipoma

A benign tumor of fat

The most common soft tissue tumor of adulthood

Age group commonly affected: middle adulthood

Pathologic Findings- Conventional Lipoma

Single or multiple subcutaneous growths that are soft, rounded or lobulated & movable against overlying skin

A well-encapsulated mass composed of sheets of mature fat cells

Arises in subcutis of proximal extremities & trunk

Lipoma

Angiolipoma

B. Liposarcoma

A malignant tumor of fat

Age group commonly affected: 40-60 y/o

Usually arises in the deep soft tissues of the proximal extremities & retroperitonemum

Liposarcoma

Histopathology

Variants depending on morphologic features:

1) Well-differentiated

2) Myxoid/Round cell

3) Pleomorphic

Histopathology-Well differentiated Liposarcoma

Tumor cells are recognized as lipocytes

Tumor cells contain supernumerary rings & giant rod chromosomes

Histopathology-Myxoid & Pleomorphic Variants

Tumor contains lipoblasts (mimic fetal fat cells)

Liposarcoma

Myxoid Liposarcoma

II. Fibrous Tumors & Tumor-like Lesions

A. Fibromatoses

1) Superficial Fibromatoses (Palmar, Plantar & Penile Fibromatoses)

2) Deep-seated Fibromatoses (Desmoid Tumors)

A1. Superficial Fibromatosis (Palmar, Plantar & Penile Fibromatoses)

Characterized by nodular or poorly defined broad fascicles of fibroblasts surrounded by abundant dense collagen

Male predominance

Fibromatosis

Variants of Superficial Fibromatoses

1. Palmar fibromatosis

2. Plantar fibromatosis

3. Penile fibromatosis

Palmar fibromatosis

Also known as Dupuytren contracture

Palmar Fibromatosis

Irregular thickening of palmar fascia ↓

W/ attachment to overlying skin↓

Puckering & dimpling of skin ↓ After some time

Progressive flexion contracture of 4th & 5th fingers of hand

Plantar Fibromatosis

Irregular or nodular thickening of plantar fascia

Flexion contractures are uncommon

Penile Fibromatoses

Also known as Peyronie disease

Presents as a palpable induration or mass on dorsolateral aspect of the penis

Penile Fibromatosis

May cause:1) Abnormal curvature of the shaft

2) Constriction of the urethra

3) Both

A2. Deep-seated Fibromatosis (Desmoid Tumors)

Present as large, infiltrative masses that frequently recur after incomplete excision

Composed of well-differentiated fibroblasts

Age predilection: At any age but

commonly in the teens-30 y/o

Types of Deep-setaed Fibromatosis

1) Extra-abdominal

2) Abdominal

3) Intra-abdominal

W/ similar gross & histologic features

Gross Pathology

Gray-white, firm, poorly demarcated masses

Rubbery & tough

Infiltrative

Extra-abdominal Fibromatosis-Gross Pathology

Sites of Origin: Musculature of:1) Shoulder

2) Chest wall

3) Back

4) Thigh

Abdominal Fibromatosis-Gross Pathology

Site of Origin: Musculoaponeurotic structures of anterior abdominal wall in ♀ during or after pregnancy

Intra-abdominal Fibromatosis

Site: Mesentery or pelvic walls in individuals w/ familial adenomatous polyposis (Gardner syndrome)

Mutations in APC or β-catenin genes

Histopathology

Plump fibroblasts arranged in broad sweeping fascicles w/c infiltrate the surrounding tissue

B. Fibrosarcoma

Gross Pathology

Site: deep soft tissues of extremities

Unencapsulated, infiltrative, soft, fish-flesh masses

(+) hemorrhage & necrosis

Histopathology

All degrees of differentiation

Resemble cellular fibromatosis

MTC arranged in a herringbone pattern

Tumors w/ architectural disarray, pleomorphism, mitotic figures & necrosis

Fibrosarcoma

Pleomorphic Fibrosarcoma

III. Fibrohistiocytic Tumors

A. Benign Fibrous Histiocytoma

Benign tumor of the soft tissue w/ a fibrohistiocytic origin

Gross Pathology

Firm, small, mobile nodule

Histopathology

Variable mixture of :-Histiocyte-like cells

▪ Some foamy▪ Others multinucleated▪ Others containing hemosiderin

-Fibroblast-like cells

Histopathology

Maybe:-Extremely cellular

Mitotic activity usually scanty or absent

B. Malignant Fibrous Histiocytoma

Phenotype of TC: fibroblastic

Now: dropped as a diagnostic entity

Histopathology

Soft tissue tumors characterized by:-Marked cytologic pleomorphism

-Bizarre multinucleate cells

-Storiform architecture

IV. Tumors of the Skeletal Muscle

A. Rhabdomyosarcoma

Types

1) Embryonal

2) Alveolar

3) Pleomorphic

Histopathology

Rhabdomyoblast-Diagnostic cell in all types

-Eccentric eosinophilic granular cytoplasm

-Round or elongate

-(+)Cross-striations

Rhabdomyosarcoma

Embryonal Rhabdomyosarcoma

Variants:1) Sarcoma botryoides2) Spindle cell type3)Anaplastic type

Age predilection: < 10 y/o

Embryonal Rhabdomyosarcoma

Sites of Origin:1) Nasal cavity2) Orbit3) Middle ear4) Prostate5) Paratesticular region

Sarcoma Botryoides

Develops in wall of mucosal-lined structures s.a. :-Nasopharynx-Common bile duct-Bladder-Vagina

Histopathology:Cambium layer

Alveolar Rhabdomyosarcoma –Gross Pathology

Site of origin: deep musculature of extremities

Alveolar Rhabdomyosarcoma-Histopathology

Fibrous septae w/c divide cell into clusters or aggregates (pulmonary alveoli)

TC-moderate size & w/ little cytoplasm

Center- dyscohesive-Periphery-TC line the septae

Alveolar Rhabdomyosarcoma

Pleomorphic Rhabdomyosarcoma-Gross Pathology

Site of origin: Deep soft tissue of adults

Pleomorphic Rhabdomyosarcoma-Histopathology

TC-large, maybe multinucleated, bizarre & eosinophilic

V. Tumors of the Smooth Muscle

A. Leiomyoma

A benign stromal tumor mainly composed of mature smooth muscle bundles

Types

1) Cutaneous 2) Genital

3) Vascular

Gross Pathology

Yellow-yellowish pink

Sharply circumscribed

Fairly firm

Leiomyoma

Histopathology

Intersecting fascicles of smooth muscle cells:-Encircle vascular lumina lined by

normal endothelial cells

No:-Mitotic activity-Necrosis-Hemorrhage

Leiomyoma

B. Leiomyosarcoma

A malignant mesenchymal tumor w/ predominantly smooth muscle differentiation

Typically :-Adults-Elderly

Gross Pathology

Location: anywhere but mostly in extremities

May arise from walls of arteries, veins, venules & arterioles

Gross Pathology

Maybe as well-circumscribed as leiomyoma but:-Larger-Softer-Tendency for:

▪ Tumor necrosis▪ Hemorrhage▪ Cystic degeneration

Leiomyosarcoma

Histopathology

Pattern of Growth:-Predominantly fascicular

-Tumor bundles intersect at wide angles

Histopathology

Cellular features:-Elongated blunt-ended nuclei

-Acidophilic fibrillary cytoplasm

Leiomyosarcoma

VI. Synovial Sarcoma

Cell of origin is unclear

Age predilection: Mostly 20-40 y/o

Gross Pathology

Location:1) Deep soft tissue (frequently the lower

extremity)

2) Head & Neck

3) Viscera

Histopathology

Maybe monophasic or biphasic

(+) Calcified concretions

Monophasic Synovial Sarcoma

Spindle cells only

Epithelial cells only

Biphasic Synovial Sarcoma

Both epithelial-like cells & mesenchymal-like cells

Epithelial cells:-Cuboidal to columnar-Pattern: form glands, cords or

aggregates

Biphasic Synovial Sarcoma

Spindle cells:-Form fascicles that surround epithelial

cells

Biphasic Synovial Sarcoma

Pathology of the Nerves

I. Peripheral Nerve Sheath TumorsA. SchwannomaB. NeurofibromaC. Malignant Peripheral Nerve Sheath

Tumor

A. Schwannoma

Usually adulthood

Location:-Cerebellopontine angle

▪Nearly all produce hearing loss▪Bilateral eighth nerve examples

are defining feature of

neurofibromatosis type 2

Location:-Can present as interventricular masses

-May involve cranial nerves other than acoustic

Gross Pathology

Cerebellopontine angle:-Nearly all originate in vestibular branch

of cranial nerve VII (Acoustic schwannoma or neuroma)

Gross Pathology

Lumbosacral spinal extramedullary space-Predilection for sensory divisions,

typically the posterior roots

-Often “dumbbell” configuration

Gross Pathology

NF-2-associated variant:-Often multilobulated growth pattern

Schwannoma

Histopathology

Antoni A and B structure

Verocay bodies

Infiltration by foamy macrophages

Vascular hyalinization

Schwannoma

B. Neurofibroma

Most are manifestations of neurofibromatosis type 1

Types

1) Cutaneous Neurofibroma

2) Plexiform Neurofibroma

Cutaneous Neurofibroma-Gross Pathology

Location: demis & subcutaneous fat

Unencapsulated masses

Cutaneous Neurofibroma-Histopathology

Spindle cells

W/ a collagenous stroma w/ little myxoid material

Plexiform Neurofibroma-Gross Pathology

Site of origin: anywhere along a nerve

Affected nerves are irregularly expanded

Plexiform Neurofibroma-Histopathology

Cell types present:-Schwann cells-Fibroblastic sells-Inflammatory cells

Loose myxoid stroma w/ areas containing collagen bundles

Plexiform Neurofibroma

C. Malignant Peripheral Nerve Sheath Tumor

Originate in:-Cranial nerve roots-Spinal Nerve roots

May arise in:-Cerebral parenchyma-Lateral ventricle

Often originate in neurofibroma

Histopathology

Variable

Majority - fibrosarcomatous, herringbone pattern is detectable focally

Densely cellular tumor

Frequent mitotic figures

Histopathology

Geographic necrosis

Histopathology

Cytologic features:-Elongated nuclei w/ tapered ends

MPNST

MPNST