Mammary lesion atlas

Duct ectasia	This lesion is characterized chiefly by dilation of ducts, inspissation of breast secretions, and a marked periductal and interstitial chronic granulomatous inflammatory reaction. The dilated ducts are filled by granular debris that contains principally lipid-laden macrophages. The periductal and interductal inflammation is manifested by heavy infiltrates of lymphocytes and macrophages, with a striking predominance of plasma cells in some cases. On occasion, granulomatous inflammation forms around cholesterol deposits. Fibrosis may eventually produce skin and nipple retraction.
Fat necrosis	Grossly, the lesion may consist of hemorrhage in the early stages and, later, central liquefactive necrosis of fat. Still later, it may appear as an ill-defined nodule of gray-white, firm tissue containing small foci of chalky white or hemorrhagic debris. The central focus of necrotic fat cells is initially surrounded by macrophages and an intense neutrophilic infiltration. Then, during the next few days, progressive fibroblastic proliferation, increased vascularization, and lymphocytic and histiocytic infiltration wall off the focus. Subsequently, foreign body giant cells, calcifications, and hemosiderin make their appearance, and eventually, the focus is replaced by scar tissue or is encysted and walled off by collagenous tissue.
Lymphocytic mastitis	This condition presents with single or multiple hard palpable masses. In some cases, the masses are bilateral or are detected as mammographic densities. The lesions are so hard that it can be difficult to obtain tissue with a needle biopsy. Microscopically, they show collagenized stroma surrounding atrophic ducts and lobules. The epithelial basement membrane is often thickened. A prominent lymphocytic infiltrate surrounds epithelium and blood vessels. This condition is most common in women with type 1 (insulin-dependent) diabetes or autoimmune thyroid disease. Therefore, it is hypothesized that this is an autoimmune disease of the breast. The only clinical significance is to distinguish this condition from carcinoma.
Granulomatous Mastitis	Granulomas in the breast are caused by a wide variety of diseases, all of them rare, and are present in fewer than 1% of all breast biopsies. Systemic granulomatous diseases (e.g., Wegener granulomatosis, sarcoidosis) may involve the breast; on occasion, the breast may be the presenting site of involvement. Infections (mycobacterial, fungal) occur, most commonly in immunocompromised patients or in the setting of a breast prosthesis or nipple piercing. Granulomatous lobular mastitis is an uncommon breast-limited disease distinguished by granulomas involving lobular epithelium. Only parous women are affected, and it is hypothesized that the disease is a hypersensitivity reaction mediated by prior alterations in lobular epithelium during lactation.
Fibrocystic disease	The basic morphologic changes are as follows: formation of cysts, apocrine metaplasia, fibrosis of the stroma, calcification, chronic inflammation, epithelial hyperplasia, and fibroadenomatoid change.

Sclerosing Adenosis	It is characterized by elongated and compressed proliferating tubules lined by two cell types that are themselves elongated along the tubular axis. The stroma is dense and may show foci of elastosis.
Microglandular Adenosis	It is characterized by small uniform glands with open lumina containing an eosinophilic secretion distributed in an irregular fashion within fibrous tissue or fat. The glands are lined by a single layer of small uniform cuboidal or flat cells with vacuolated or granular cytoplasm, lacking apocrine-type "snouts.".
Radial scar	It is characterized by densely fibrotic connective tissue center with clumps of basophilic material, strongly reactive for elastic tissue stain. Embedded within this stroma are small disorganized ductular formations, at the periphery of the spokes are larger dilated ducts that may exhibit epithelial hyperplastic changes. Some obliterated ducts are also seen.
Tubular adenoma	A close packing of uniform small tubules lined by a single layer of epithelial cells and an attenuated layer of myoepithelial cells is seen; the stroma is characteristically sparse. Sometimes this pattern is seen combined with that of a fibroadenoma, suggesting that the two processes are closely related.
Lactating adenoma	It composed microscopically of proliferated glands lined by actively secreting cuboidal cells.
Ductal adenoma	It presents as an encapsulated solid intraductal tumor composed of arrays of long, narrow tubules composed of a dual population of epithelial and myoepithelial cells and a modest amount of fibrous tissue.

Central Papilloma	Papillomas are complex, cellular, and often intricately arborescent. Features favoring benignancy in a papillary breast lesion are a well-developed stroma in the papillary folds, the presence of two cell types, normochromatic and often oval nuclei, scanty mitotic activity, the presence of apocrine metaplasia, and a lack of cribriform or trabecular patterns. Tumor necrosis is nearly always absent.
Peripheral papillomas	Multiple, arise in smaller ducts.
Intraductal papillary carcinoma	The features favoring carcinoma are uniformity in size and shape of the epithelial cells (whether round, oval, or spindle), presence of one cell type only (i.e., lack of myoepithelial cells), nuclear hyperchromasia and high nucleocytoplasmic ratio, high mitotic activity, lack of apocrine metaplasia, cribriform and trabecular patterns, scanty or absent stroma, and lack of benign proliferative disease in the adjacent breast.
Intracystic papillary carcinoma	This tumor appears as a mural nodule within a large cystic space supposedly representing a dilated duct.

Atypical ductal hyperplasia	Proliferative lesion in which some but not all of the features of intraductal carcinoma are present.
Ductal carcinoma in situ	Several morphologic variants of DCIS exist, it is divided in a three-grade on the basis of cytologic criteria: grade 1 (solid/cribriform/micropapillary) which composed of smaller uniform cells unassociated with necrosis, grade 3 (comedocarcinoma) which characterized by large pleomorphic cells associated with necrosis, and those showing intermediate cytologic features are reported as grade 2. /
Atypical lobular hyperplasia	Proliferative lesion in which some but not all of the features of lobular carcinoma in situ are present.
Lobular carcinoma in situ	In this lesion the lobules are distended and completely filled by relatively uniform, round, small to medium-sized cells with round and normochromatic (or only mildly hyperchromatic) nuclei.

Ductal carcinoma	This tumor can grow in diffuse sheets, well-defined nests, cords, or as individual cells. Glandular/tubular differentiation may be well developed, barely detectable, or altogether absent. The tumor cells vary in size and shape, but by definition they are larger and more pleomorphic than those of invasive lobular carcinomas, their nuclei and nucleoli are more prominent, and mitotic figures are more numerous. Areas of necrosis occur in about 60% of the cases.
Lobular carcinoma	It is characterized by the presence of small and relatively uniform tumor cells growing singly, in Indian file, and in a concentric ("pagetoid") fashion around lobules involved by in situ lobular neoplasia. Gland formation is not a feature of classic ILC. The stroma is usually abundant, is of dense fibrous type, and contains foci of periductal and perivenous elastosis in virtually every case.
Tubular carcinoma	It simulates a benign condition (particularly radial scar and microglandular adenosis) because of the well-differentiated nature of the glands, absence of necrosis or mitoses, and scanty pleomorphism. The clues to the diagnosis are the haphazard arrangement of the glands in the stroma with absence of any organoid configuration; frequent invasion of fat at the periphery of the lesion; irregular and often angulated contours of the glands; open lumina with basophilic secretion; apocrine-type "snouts" in the apical cytoplasm; formation of trabecular bars; lack of a myoepithelial cell component lack of basement membrane; and occurrence in two thirds or more of the cases of typical intraductal carcinoma in ducts within or outside the lesion, nearly always of micropapillary or cribriform type.
Invasive cribriform and papillary carcinoma	It is closely related to tubular carcinoma and sharing with it an excellent prognosis. As the name indicates, the tumor has a cribriform appearance similar to that seen in the more common in situ counterpart, but it also exhibits stromal invasion. This pattern is often seen in association with tubular formations, the relative proportion of the two elements determining the term used. Most papillary carcinomas of the breast are entirely or predominantly in situ lesions. The invasive component of a papillary carcinoma also may be papillary or have the features of an ordinary ductal-type carcinoma; the prognosis is substantially better for the former.
Invasive micropapillary carcinoma
Metaplastic carcinoma	It is a generic term for breast carcinoma of ductal type in which the predominant component of the neoplasm has an appearance other than epithelial and glandular. It includes the following categories: -sarcomatoid carcinoma (carcinoma with sarcoma-like stroma), and carcinosarcoma. -Spindle-cell carcinoma. -Carcinoma with osteoclastic giant cells. -Squamous cell carcinoma.
Medullary carcinoma	It is characterized by pushing borders. The pattern of growth is diffuse, with minimal or no glandular differentiation or intraductal growth and absence of mucin secretion. The tumor cells are large and pleomorphic, with large nuclei and prominent nucleoli and numerous mitoses. The cell borders are indistinct, giving the tumor a syncytial appearance. Spindle cell metaplasia, bizarre tumor giant cells, extensive necrosis, and the absence of calcification are other common features.A constant microscopic component is a prominent lymphoplasmacytic infiltrate at the periphery of the tumor.
Adenoide cystic carcinoma
Mucinous carcinoma	It is manifested by small clusters of tumor cells "floating in a sea of mucin". These clusters may be solid or exhibit acinar formations. The mucin is almost entirely extracellular.
Signet ring cell carcinoma	In this type a significant number of tumor cells show intracytoplasmic mucin accumulation, resulting in the typical signet ring appearance.
Apocrine carcinoma	It is composed entirely or predominantly of apocrine-type epithelium. The large tumor cells have an abundant acidophilic, somewhat granular cytoplasm, which may contain eosinophilic or golden brown granules that are strongly PAS positive. The nuclei are vesicular and nucleoli are prominent. Glandular differentiation is usually found, the luminal portion of the tumor having a characteristic bulbous expansion ("apocrine snout").
Lipid rich carcinoma

Fibroadenoma	It vary in appearance from case to case depending on the relative amounts of glandular and connective tissue. The tubules are composed of cuboidal or low columnar cells with round uniform nuclei resting on a myoepithelial cell layer. The stroma is usually made up of loose connective tissue.
Complex Fibroadenoma	Fibroadenomas with cysts, sclerosing adenosis, calcifications, or papillary apocrine changes are referred to as "complex".
Juvenile fibroadenoma	It tends to occur in adolescents, reach a large size (over 10 cm), and show hypercellularity of glands and/or stroma.
Phyllodes Tumour (low grade)	The two key features of phylloides tumor are stromal hypercellularity and the presence of benign glandular elements as an integral component of the neoplasm. The low grade type has the configuration of fibroadenomas with a cellular stroma without atypical features
Phyllodes Tumour (high grade)	The high grade type has marked nuclear atypia, numerous mitoses, and loss of the relationship between glands and stroma.
Mammary hamartoma

Myoepitheliosis

It should be recognized that myoepithelial participation is an integral component of benign proliferative breast diseases (such as sclerosing adenosis, ductal hyperplasia, intraductal papilloma, and nipple adenoma) and that in some instances it dominates the histologic picture. Such cases, when presenting in the form of multifocal microscopic lesions, have been designated as myoepitheliosis.

Adenomyoepithelioma

It is a small (~1 cm), firm, well-circumscribed tumor microscopically composed of cells of polygonal shape and optically clear cytoplasm, arranged in nests sometimes centered by gland-forming epithelial cells.The patterns of growth may be spindle-cell (myoid), tubular, or lobulated.

Malignant myoepithelioma

It is purely composed of myoepithelial cells and is cytologically malignant.

Pseudo-angiomatous Hyperplasia
Hemangioma
Angiosarcoma	The diagnostic areas are characterized by anastomosing vascular channels lined by atypical endothelial cells.
Lipoma
Breast Lymphoma	Primary lymphoma of the breast is almost always of non-Hodgkin's type and usually has a diffuse pattern of growth. In adult patients, the most common lymphoma is the large cell type, followed by small lymphocytic and follicular types; nearly all of these tumors are of B-cell nature.
Metastatic Tumours	Malignant melanoma and carcinoma of the lung, ovary, kidney, and stomach are the most common sources.
Male gynecomastia	In this lesion the ducts show a variable and sometimes very prominent degree of epithelial hyperplasia and are surrounded by a prominent swollen stroma.