terminal duct–lobular unit (tdlu). a diagrammatic ...two different breast lesions diagnosed as...

Terminal ductTerminal duct––lobular unit (TDLU). lobular unit (TDLU). AA, , Diagrammatic representation of this structure. Diagrammatic representation of this structure.

ETD = ETD = ExtralobularExtralobular terminal duct; ITD = terminal duct; ITD = intralobularintralobular terminal duct. terminal duct.

Mammary glandMammary gland

Terminal ductTerminal duct––lobular unit (TDLU). lobular unit (TDLU). BB, , Photomicrograph of this unit as seen in a normal Photomicrograph of this unit as seen in a normal

adult female. adult female.

Mammary glandMammary gland

ImmunocytochemicalImmunocytochemical markers of mammary markers of mammary lobule. lobule. AA, , LactalbuminLactalbumin, showing , showing positivitypositivity in in

secretorysecretory epithelium and epithelium and intraglandularintraglandular luminalumina. .

ImmunocytochemicalImmunocytochemical markers of mammary lobule. markers of mammary lobule. BB, , ActinActin, showing , showing positivitypositivity in the outer in the outer myoepithelialmyoepithelial cell cell component. Smooth muscle cells present in adjacent component. Smooth muscle cells present in adjacent

vessel walls serve as builtvessel walls serve as built--in controls. in controls.

LactationalLactational changes in mammary lobule. There is changes in mammary lobule. There is marked marked cytoplasmiccytoplasmic vacuolization. vacuolization.

Cystic involution of lobule. This is an ageCystic involution of lobule. This is an age--related related change of no clinical significance. change of no clinical significance.

AA, Pregnancy, Pregnancy--like changes in mammary lobule. like changes in mammary lobule. These two clinically inconsequential alterations These two clinically inconsequential alterations

may coexist. may coexist.

BB, Clear cell changes. These two clinically , Clear cell changes. These two clinically inconsequential alterations may coexist. inconsequential alterations may coexist.

Gross appearance of mammary duct Gross appearance of mammary duct ectasiaectasia. . Some of the dilated ducts contain a thick dark Some of the dilated ducts contain a thick dark

material. material.

PostPost--traumatic fat necrosis involving breast. traumatic fat necrosis involving breast.

Retraction of skin in a patient with fat necrosis Retraction of skin in a patient with fat necrosis (arrow), as seen in a photograph taken from a (arrow), as seen in a photograph taken from a

wellwell--seasoned paper. seasoned paper.

SclerosingSclerosing lymphocyticlymphocytic mastitis in a diabetic mastitis in a diabetic woman. Some of the lymphocytes infiltrate the woman. Some of the lymphocytes infiltrate the

gland. gland.

Florid Florid granulomatousgranulomatous reaction to silicone. Foamy reaction to silicone. Foamy macrophages, foreign bodymacrophages, foreign body--type multinucleated type multinucleated

giant cells, and lymphocytes are present. giant cells, and lymphocytes are present.

Gross appearance of Gross appearance of fibroadenomafibroadenoma. The lesion is . The lesion is sharply circumscribed and perfectly round, and it sharply circumscribed and perfectly round, and it

contains numerous slits. contains numerous slits.

Microscopic appearance of Microscopic appearance of fibroadenomafibroadenoma. The . The tumor shown in tumor shown in BB has a slightly has a slightly hypercellularhypercellularstromastroma but not to a degree that would justify a but not to a degree that would justify a

diagnosis of diagnosis of phyllodesphyllodes tumor. tumor.

Heavy, coarse calcification in a large breast Heavy, coarse calcification in a large breast fibroadenomafibroadenoma as seen in a mammogram. as seen in a mammogram.

FibroadenomaFibroadenoma with with apocrineapocrine metaplasiametaplasia. . AA, , HematoxylinHematoxylin––eosin section showing a prominent eosin section showing a prominent

discontinuous layer of plump discontinuous layer of plump eosinophiliceosinophilic cells at the cells at the base of the gland. These should not be confused with base of the gland. These should not be confused with

neuroendocrineneuroendocrine cells. cells.

FibroadenomaFibroadenoma with with apocrineapocrine metaplasiametaplasia. . BB, , ImmunostainImmunostain for GCDFPfor GCDFP--15. 15.

Giant Giant fibroadenomafibroadenoma occurring in an adolescent occurring in an adolescent female. female.

FibroadenomaFibroadenoma with focal involvement by lowwith focal involvement by low--grade grade intraductalintraductal carcinoma. carcinoma.

Gross appearance of lactating adenoma. The Gross appearance of lactating adenoma. The mass has a distinct lobular configuration, mass has a distinct lobular configuration,

yellowish color, and marked yellowish color, and marked vascularizationvascularization. .

SoSo--called called ““lactating adenoma.lactating adenoma.”” The The hyperplastichyperplasticlobules show marked lobules show marked cytoplasmiccytoplasmic vacuolization. vacuolization.

Gross appearance of Gross appearance of intraductalintraductal papillomapapilloma. A . A polypoidpolypoid mass is seen protruding within the mass is seen protruding within the

lumen of a markedly dilated duct. lumen of a markedly dilated duct.

IntraductalIntraductal papillomapapilloma. . AA, Low, Low--power appearance power appearance showing complex showing complex arborizingarborizing architecture. architecture.

IntraductalIntraductal papillomapapilloma. . BB, High, High--power view power view showing dual cell composition, with a wellshowing dual cell composition, with a well--defined defined

row of row of myoepithelialmyoepithelial cells. cells.

Gross appearance of Gross appearance of papillomapapilloma presenting as a presenting as a mural nodule within a cyst. mural nodule within a cyst.

PapillomaPapilloma of breast showing entrapment of of breast showing entrapment of epithelial structures by epithelial structures by fibrohyalinefibrohyaline stromastroma, , resulting in a resulting in a pseudoinvasivepseudoinvasive appearance. appearance.

Typical Typical polypoidpolypoid shape of nipple adenoma, as shape of nipple adenoma, as seen in a whole mount. seen in a whole mount.

Nipple adenoma. The complex architectural Nipple adenoma. The complex architectural arrangement can lead to arrangement can lead to overdiagnosisoverdiagnosis. The . The

continuity with the continuity with the squamoussquamous epithelium of the epithelium of the skin is a typical feature of this entity. skin is a typical feature of this entity.

SclerosingSclerosing adenosisadenosis. . AA, Low, Low--power view. The power view. The lobular configuration of the lesion is obvious. lobular configuration of the lesion is obvious.

SclerosingSclerosing adenosisadenosis. . BB, Medium, Medium--power view. power view. Note the spindle shape of the proliferating cells in Note the spindle shape of the proliferating cells in the center of the lobule and the the center of the lobule and the fibrillaryfibrillary quality of quality of the cytoplasm, indicative of the cytoplasm, indicative of myoepithelialmyoepithelial nature. nature.

SclerosingSclerosing adenosisadenosis. . CC, , ImmunocytochemicalImmunocytochemicalstain for stain for actinactin showing strong showing strong immunoreactivityimmunoreactivity in in

the the myoepithelialmyoepithelial cell component. cell component.

SclerosingSclerosing adenosisadenosis. . DD, , SclerosingSclerosing adenosisadenosis with with lobular carcinoma in situ. Note the regularity of lobular carcinoma in situ. Note the regularity of the edge and absence of infiltrative features. the edge and absence of infiltrative features.

Benign Benign ““perineurialperineurial invasioninvasion”” in a breast lesion in a breast lesion that had elsewhere the typical features of that had elsewhere the typical features of

sclerosingsclerosing adenosisadenosis. .

Involvement of the wall of a vessel by Involvement of the wall of a vessel by sclerosingsclerosingadenosisadenosis, as highlighted by the , as highlighted by the VerhoeffVerhoeff––van van

GiesonGieson stain. stain.

MicroglandularMicroglandular hyperplasia. hyperplasia. AA, Low, Low--power power appearance, showing haphazardly scattered appearance, showing haphazardly scattered

small round glands. small round glands.

MicroglandularMicroglandular hyperplasia. hyperplasia. BB, On high power, , On high power, the glands are open and contain a luminal the glands are open and contain a luminal

secretion. The secretion. The myoepithelialmyoepithelial cell layer is not cell layer is not discernible. discernible.

AdenomyoepithelialAdenomyoepithelial adenosisadenosis. The glands are relatively . The glands are relatively large, with a wide, open lumen and large, with a wide, open lumen and apocrineapocrine metaplasiametaplasia. .

The cellular component in between is composed of The cellular component in between is composed of myoepithelialmyoepithelial cells. cells. BB, S, S--100 Protein stain highlights the 100 Protein stain highlights the

prominent prominent myoepithelialmyoepithelial component. component.

Fibrocystic changes, including cystic dilatation, Fibrocystic changes, including cystic dilatation, apocrineapocrine metaplasiametaplasia, florid , florid ductalductal hyperplasia, hyperplasia,

and fibrosis. and fibrosis.

Photomicrograph demonstrating florid Photomicrograph demonstrating florid ductalductal hyperplasia. There is hyperplasia. There is no evidence of necrosis, and individual cells are well supportedno evidence of necrosis, and individual cells are well supported by by

their their stromastroma. A prominent cleft has formed between a solid . A prominent cleft has formed between a solid intraluminalintraluminal proliferation and an outer epithelial row. This feature proliferation and an outer epithelial row. This feature

is usually indicative of a benign condition. is usually indicative of a benign condition.

Florid Florid ductalductal hyperplasia. Note the oval shape of hyperplasia. Note the oval shape of the nuclei and the parallel arrangement, resulting the nuclei and the parallel arrangement, resulting

in a in a ““streamingstreaming”” effect. effect.

Structure resembling a renal Structure resembling a renal glomerulusglomerulus in florid in florid ductalductal hyperplasia. hyperplasia.

DuctalDuctal hyperplasia showing irregularly shaped hyperplasia showing irregularly shaped ridges connecting opposite portions of the wall. ridges connecting opposite portions of the wall. Note the fact that the oval nuclei are arranged Note the fact that the oval nuclei are arranged

parallel to the long axis of the ridge. parallel to the long axis of the ridge.

CollagenousCollagenous spherulosisspherulosis. The cylinders have a . The cylinders have a round shape and a homogeneous pink staining round shape and a homogeneous pink staining quality, consistent with basement membrane quality, consistent with basement membrane

material. material.

Gross appearance of radial scar. Gross appearance of radial scar.

Typical Typical stellatestellate shape of radial scar as seen on shape of radial scar as seen on low power. low power.

Abundant deposition of elastic tissue in the Abundant deposition of elastic tissue in the central portion of a radial scar, as highlighted by central portion of a radial scar, as highlighted by

the the VerhoeffVerhoeff––van van GiesonGieson stain. stain.

AA, Benign , Benign ductularductular structures entrapped in radial structures entrapped in radial scar. Note their regular contour and the scar. Note their regular contour and the

hypocellularhypocellular hyaline quality of the hyaline quality of the stromastroma. .

BB, Tubular carcinoma shown for comparison. , Tubular carcinoma shown for comparison. Note the angulated shape of the glands and the Note the angulated shape of the glands and the

desmoplasticdesmoplastic stromastroma. .

Radial scar with associated lowRadial scar with associated low--grade grade intraductalintraductalcarcinoma. carcinoma.

Two different breast lesions diagnosed as atypical Two different breast lesions diagnosed as atypical lobular hyperplasia by four experts in breast pathology. lobular hyperplasia by four experts in breast pathology. There is lobular enlargement and proliferation, but some There is lobular enlargement and proliferation, but some

luminalumina are preserved, and there is only minimal are preserved, and there is only minimal distention of individual units. distention of individual units.

Two different breast lesions diagnosed as atypical Two different breast lesions diagnosed as atypical ductalductalhyperplasia by two experts in breast pathology. There is hyperplasia by two experts in breast pathology. There is marked epithelial proliferation in structures of marked epithelial proliferation in structures of ductalductal type type

associated with associated with atypiaatypia, but they were felt not to fulfill , but they were felt not to fulfill criteria for carcinoma in situ. criteria for carcinoma in situ.

ProliferativeProliferative ductalductal lesion diagnosed as atypical lesion diagnosed as atypical ductalductal hyperplasia on account of the hyperplasia on account of the

cytoarchitecturalcytoarchitectural features and small size. features and small size.

Flat epithelial Flat epithelial atypiaatypia. The spaces are dilated and . The spaces are dilated and lined by columnar epithelium showing scanty lined by columnar epithelium showing scanty

atypiaatypia. .

LowLow--power area of calcification power area of calcification

HighHigh--power views of the corresponding power views of the corresponding microscopic specimen. microscopic specimen.

Specimen from a fine needle aspiration (FNA) biopsy. Specimen from a fine needle aspiration (FNA) biopsy. This was diagnosed as breast carcinoma and followed This was diagnosed as breast carcinoma and followed by the performance of a mastectomy, which confirmed by the performance of a mastectomy, which confirmed

the the cytologiccytologic interpretation. interpretation.

CytologicCytologic features of various types of breast features of various types of breast lesions as seen in FNA specimens: lesions as seen in FNA specimens: AA, ,

fibroadenomafibroadenoma. .

CytologicCytologic features of various types of breast features of various types of breast lesions as seen in FNA specimens: lesions as seen in FNA specimens: BB, , apocrineapocrine

metaplasiametaplasia. .

CytologicCytologic features of various types of breast features of various types of breast lesions as seen in FNA specimens: lesions as seen in FNA specimens: CC, invasive , invasive

ductalductal carcinoma. carcinoma.

CytologicCytologic features of various types of breast features of various types of breast lesions as seen in FNA specimens: lesions as seen in FNA specimens: DD, invasive , invasive

ductalductal carcinoma. carcinoma.

CytologicCytologic features of various types of breast features of various types of breast lesions as seen in FNA specimens: lesions as seen in FNA specimens: EE, , medullarymedullary

carcinoma. carcinoma.

CytologicCytologic features of various types of breast features of various types of breast lesions as seen in FNA specimens: lesions as seen in FNA specimens: FF, , mucinousmucinous

carcinoma. carcinoma.

CytologicCytologic features of various types of breast features of various types of breast lesions as seen in FNA specimens: lesions as seen in FNA specimens: GG, invasive , invasive

lobular carcinoma. lobular carcinoma.

BiopsyBiopsy--induced induced artifactualartifactual changes: changes: AA, tumor , tumor cells along needle tract. cells along needle tract.

BiopsyBiopsy--induced induced artifactualartifactual changes: changes: BB, tumor , tumor cells in lumen of lymph vessel. cells in lumen of lymph vessel.

BiopsyBiopsy--induced induced artifactualartifactual changes: changes: CC, tumor , tumor cells in lumen of artery. cells in lumen of artery.

In situ In situ ductalductal carcinoma with carcinoma with comedocomedo--type type necrosis. necrosis.

Preservation of a Preservation of a myoepithelialmyoepithelial cell layer in highcell layer in high--grade grade intraductalintraductal carcinoma. (Smooth muscle carcinoma. (Smooth muscle

actinactin immunostainimmunostain) )

Invasive Invasive ductalductal carcinoma associated with carcinoma associated with extensive extensive intraductalintraductal carcinoma component. carcinoma component.

IntracysticIntracystic carcinoma of the breast. The papillary carcinoma of the breast. The papillary configuration of the tumor is already grossly configuration of the tumor is already grossly

evident. evident.

HighHigh--power view of an in situ papillary carcinoma. power view of an in situ papillary carcinoma. Note the layering of cells, loss of nuclear polarity, Note the layering of cells, loss of nuclear polarity,

marked marked hyperchromasiahyperchromasia, and lack of a , and lack of a myoepithelialmyoepithelial cell layer. cell layer.

In situ papillary carcinoma. The In situ papillary carcinoma. The arborizingarborizing nature nature of this tumor and the stout of this tumor and the stout fibrovascularfibrovascular core are core are not too different from those of a benign not too different from those of a benign papillomapapilloma. .

Papillary carcinoma with soPapillary carcinoma with so--called called ““globoidgloboid”” or or ““clear clear cells.cells.”” These cells, which are These cells, which are immunoreactiveimmunoreactive for for

GCDFPGCDFP--15, should not be confused with 15, should not be confused with myoepithelialmyoepithelialcells. cells. BB, Negative , Negative immunostainimmunostain for smooth muscle for smooth muscle actinactin. .

Solid type of in situ Solid type of in situ ductalductal carcinoma. There is no carcinoma. There is no necrosis. necrosis.

LowLow--grade in situ grade in situ ductalductal carcinoma of carcinoma of cribriformcribriformtype. type.

TrabecularTrabecular bars in bars in intraductalintraductal carcinoma. Note carcinoma. Note the perpendicular arrangement of the nuclei in the perpendicular arrangement of the nuclei in

relation to the long axis of the bars. relation to the long axis of the bars.

MicropapillaryMicropapillary carcinoma of breast. Some of the carcinoma of breast. Some of the papillae lack a central papillae lack a central fibrovascularfibrovascular core. core.

DuctalDuctal carcinoma in situ of socarcinoma in situ of so--called called ““clinging type.clinging type.”” One One or two layers of atypical cells line dilated glandular or two layers of atypical cells line dilated glandular

structures containing granular structures containing granular intraluminalintraluminal material in material in which ghosts of tumor cells are identified. which ghosts of tumor cells are identified.

SoSo--called called ““lobular lobular cancerizationcancerization..”” The lobule is markedly The lobule is markedly expanded and composed of relatively large tumor cells expanded and composed of relatively large tumor cells with the appearance of with the appearance of ductalductal--type carcinoma. Typical type carcinoma. Typical

ductalductal carcinoma was present elsewhere in the carcinoma was present elsewhere in the specimen. specimen.

ApocrineApocrine variant of in situ variant of in situ ductalductal carcinoma. carcinoma.

EndocrineEndocrine--type type ductalductal carcinoma in situ: carcinoma in situ: AA, , hematoxylinhematoxylin––eosin. eosin.

EndocrineEndocrine--type type ductalductal carcinoma in situ: carcinoma in situ: BB, , chromograninchromogranin. .

Typical pattern of involvement of terminal ductTypical pattern of involvement of terminal duct––lobular unit by lobular carcinoma in situ. lobular unit by lobular carcinoma in situ.

Marked expansion of a lobular unit by lobular Marked expansion of a lobular unit by lobular carcinoma in situ. A few small spaces are still carcinoma in situ. A few small spaces are still

present in the smaller focus. present in the smaller focus.

Involvement of duct by lobular carcinoma in situ. Involvement of duct by lobular carcinoma in situ. In the presence of such change, a thorough In the presence of such change, a thorough

search for typical areas of lobular involvement search for typical areas of lobular involvement should be undertaken. should be undertaken.

Typical gross appearance of invasive Typical gross appearance of invasive ductalductal carcinoma. carcinoma. Note the irregular (crabNote the irregular (crab--like) shape of the tumor, white like) shape of the tumor, white fibrous appearance, and chalky streaks. Retraction of fibrous appearance, and chalky streaks. Retraction of the overlying skin is obvious in the specimen shown in the overlying skin is obvious in the specimen shown in

BB. .

AA, Gross appearance of typical invasive , Gross appearance of typical invasive ductalductalcarcinoma. carcinoma. ““Chalky streaksChalky streaks”” can be seen can be seen

throughout the tumor. A central space can be throughout the tumor. A central space can be identified in some of them (arrows). identified in some of them (arrows).

BB, Elastic tissue stain of the lesion illustrated in A , Elastic tissue stain of the lesion illustrated in A showing that showing that ““chalky streakschalky streaks”” correspond to a markedly correspond to a markedly

thickened elastic layer in the wall of nonthickened elastic layer in the wall of non--neoplasticneoplastic ducts ducts crossing the tumor. (crossing the tumor. (BB, , VerhoeffVerhoeff––van van GiesonGieson) )

Prototypical invasive Prototypical invasive ductalductal carcinoma. carcinoma.

Vascular invasion by breast carcinoma Vascular invasion by breast carcinoma demonstrated by demonstrated by positivitypositivity of endothelial cells for of endothelial cells for

UlexUlex europaeuseuropaeus lectinlectin I. I.

Tubular carcinoma of breast. The angulated Tubular carcinoma of breast. The angulated shape of the glands and the cellular shape of the glands and the cellular stromastroma are are

characteristic of this lesion. characteristic of this lesion.

Invasive Invasive cribriformcribriform carcinoma. Some of the carcinoma. Some of the nodules have a predominantly solid appearance. nodules have a predominantly solid appearance.

Typical gelatinous gross appearance of pure Typical gelatinous gross appearance of pure mucinousmucinous carcinoma. Note the sharply carcinoma. Note the sharply

circumscribed quality of the tumor. circumscribed quality of the tumor.

MucinousMucinous carcinoma of the breast. Clusters of carcinoma of the breast. Clusters of wellwell--differentiated tumor cells are seen floating in differentiated tumor cells are seen floating in

a sea of a sea of mucinmucin. .

Argyrophilic cells present in another case of mucinouscarcinoma of the breast, indicative of neuroendocrine

differentiation. (Sevier–Munger stain)

Early form of mucin-producing low-grade carcinoma showing the mechanism of formation of the epithelial

strips typically seen floating in the mucin.

Gross appearance of medullary carcinoma. Note the well-circumscribed character and fleshy

appearance.

Medullary carcinoma. The large tumor cells grow in a “syncytial” fashion and are sharply separated from the

surrounding stroma, which is heavily infiltrated by lymphocytes and plasma cells.

Gross appearance of secretory carcinoma. The tumor is well circumscribed and shows a

variegated cut surface.

Secretory carcinoma. The small uniform glands are filled by a secretory material.

Breast carcinoma with neuroendocrinedifferentiation (so-called “carcinoid tumor of

breast”).

Strong reactivity for chromogranin in breast carcinoma with neuroendocrine differentiation.

Gross appearance of metaplastic carcinoma. A large, fleshy mass is seen protruding inside a cavity.

Microscopically, this tumor showed an admixture of squamous and spindle elements.

Metaplastic carcinoma. The tumor shown in A exhibits a blending of the carcinomatous and sarcoma-like components, whereas that depicted in B has a biphasic (“carcinosarcomatous”) appearance.

Large tumor embolus in a dermal lymph vessel in a case with the clinical appearance of

inflammatory carcinoma.

Eczema-like hyperemic and eroded clinical appearance of Paget’s disease.

Low-power views of Paget’s disease. The cleft-like separation between the tumor cells and the overlying squamous epithelium is characteristic.

High-power views of Paget’s disease. The cleft-like separation between the tumor cells and the overlying squamous epithelium is characteristic.

Melanin colonization in breast carcinoma as seen with argentaffin stain.

Immunohistochemical demonstration of malignant intraepithelial cells in Paget’s disease: A, EMA

immunostain.

Immunohistochemical demonstration of malignant intraepithelial cells in Paget’s disease: B,

HER2/neu immunostain.

Biopsy of nipple showing scattered clear cells in the basal layer (“Toker’s cells”). These cells show a mild

degree of nuclear atypia and were immunohistochemically similar to the cells of Paget’s

disease.

Invasive lobular carcinoma. The tumor cells are small and uniform with round nuclei and grow in

an Indian file fashion.

Typical target-like growth of tumor cells around an uninvolved duct in invasive lobular

carcinoma.

Indian file pattern of growth of invasive lobular carcinoma.

Pleomorphic variant of invasive lobular carcinoma.

Cytoplasmic vacuolization with nuclear displacement in breast carcinoma due to lipid

accumulation.

Signet ring carcinoma of the breast, this is regarded as a variant of lobular carcinoma. B,

Alcian blue–PAS stain.

Immunocytochemical stain for estrogen receptors in invasive breast carcinoma. The strong nuclear

positivity in tumor cells is shown against a negative cytoplasmic and stromal background.

Strong (3+) membrane immunoreactivity for HER2/neu in high-grade breast carcinoma.

Breast carcinoma metastatic to vertebra. The normal bone marrow has been flushed out by placing a thin

slice of tissue under a strong jet of water.

Metastasis of mammary lobular carcinoma to lamina propria of large bowel mucosa. B,

Keratin 7 immunostain.

Cluster of metastatic cells in sentinel lymph node highlighted with keratin stain.

Breast implant (left) surrounded by a thick fibrous wall that has undergone heavy calcification

(right).

Striking vacuolization of breast carcinoma cells induced by chemotherapy. The appearance simulates that of histiocytes. The tumor cells shown in B are located

within a blood vessel.

Benign mixed tumor of breast. A prominent myxochondroid stroma is interspersed among

the glandular structures.

Adenoid cystic carcinoma of breast. The appearance is similar to that of its more

common homolog in salivary glands.

Adenomyoepithelioma. In some areas there is a clear relationship between the secretory and the myoepithelial component

(similar to that seen in adenomyoepitheliosis), but in others the spindle myoepithelial cells become the exclusive neoplastic

element.

Gross appearance of phylloides tumor. The tumor shown in A exhibits the typical appearance of the cut

surface. The tumor illustrated in B has undergone extensive hemorrhagic infarct.

Two views of low-grade phylloides tumor, showing cleft-like spaces and concentration of

tumor cells beneath the epithelium.

Phylloides tumor with adipose tissue differentiation of the neoplastic stromal

component.

Typical hemorrhagic gross appearance of angiosarcoma of breast.

Extremely well-differentiated angiosarcoma of breast.

Complex anastomosing vascular pattern in angiosarcoma of breast.

Benign hemangioendothelioma of breast in a child. The appearance is identical to that of the homologous

tumor seen more commonly in skin or salivary gland.

Epithelioid (histiocytoid) hemangioma located within the breast substance.

Sarcoma of breast. The entrapped epithelial tissue lacks the features of a phylloides tumor.

MALT-type malignant lymphoma of breast. Some of the neoplastic lymphocytes infiltrate the

glandular structures.

Granulocytic sarcoma of breast. It is easy to misdiagnose this lesion as a large cell

lymphoma.

Gross appearance of so-called “hamartoma of breast.”There is a combination of cystic dilatation of ducts,

fibrosis, and entrapment of adipose tissue. This lesion is more distinctive and impressive grossly than

microscopically.

Glandular epithelium and fibrous stroma with distorted arrangement in hamartoma of breast.

So-called “myoid hamartoma of breast.”

Gross appearance of fibromatosis involving breast. The mass is solid and ill defined.

Pseudoangiomatous stromal hyperplasia. Thin channels lined by spindle cells are seen

scattered within a hyalinized stroma.

Bizarre multinucleated cells in mammary stroma. This neoplastic change is analogous to that more often seen in the stroma of the upper aerodigestive tract

and in the genital tract.

So-called “virginal hypertrophy of breast,”showing proliferative changes in epithelium and

stroma.

Juvenile papillomatosis (Swiss cheese disease). The gross appearance is that of clustered cystic

formations.

Juvenile papillomatosis (Swiss cheese disease). Whole-mount view showing variously sized cystic formations,

alternating with solid epithelial proliferations.

Epithelial proliferation surrounded by a hypocellular myxoid halo in gynecomastia.

Myofibroblastoma of male breast. The microscopic appearance is very reminiscent of

solitary fibrous tumor.

Carcinoma of the male breast composed of well-differentiated tumor cells with abundant

granular cytoplasm having oncocytic features.

Grading of the immunohistochemical staining for HER2/neu overexpression

terminal duct–lobular unit (tdlu). a diagrammatic ...two different breast lesions diagnosed as...

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