Papillary carcinomas of the breast (PCB), also termed malignant papillary carcinomas of the breast, are rare forms of the breast cancers. The World Health Organization (2019) classified papillary neoplasms (i.e. benign or cancerous tumors) of the breast into 5 types: intraductal papilloma, papillary ductal carcinoma in situ (PDCIS), encapsulated papillary carcinoma (EPC), solid-papillary carcinoma (SPC), and invasive papillary carcinoma (IPC). The latter four carcinomas are considered here; intraductal papilloma is a benign neoplasm. The World Health Organization regarded solid papillary carcinoma as having two subtypes: in situ and invasive SPC. PCB develop from the epithelial cells that line the outer surfaces of ducts leading from exocrine glands or organs, blood vessels, or inner surfaces of the cavities in many internal organs. PCB are carcinomas derived from the epithelial cells of mammary gland ducts. They are a clinically, histologically, and biologically heterogeneous group of breast cancers that are often difficult to distinguish from each other as well as from other papillary breast lesions. The identification of PBS tumors may require the input of breast pathologists familiar with papillary lesions of the breast. The four types of PCB are defined and diagnosed in part by several of their microscopic features including: 1) the presence of tumor invasion into adjacent normal tissues; 2) the presence and location of myoepithelial cells, i.e. cells that normally rest on the basement membrane of mammary gland ducts and function to contract and thereby expel milk from mammary glands (these cells are identified by immunohistochemistry staining tumor tissue with, e.g. cytokeratin 5/6 antibodies that detect two markers of myoepithelial cells, cytokeratin 5 and keratin 6A); 3) the presence of a thick fibrous capsule enclosing the carcinoma; 4) the presence of areas of neuroendocrine differentiation, i.e. sites of accumulated neoplastic cells with features combining those of nerve and hormone-producing cells including in particular the presence of neurosecretory granules, i.e. cytoplasmic granules about 180 nanometers in diameter that are found in neurons and secretory cells; and 5) the presence of signet ring-shaped cells bearing mucin-containing granules.
Papillary ductal carcinoma in situ
Presentation Information on the frequency and clinical features of PDCIS is limited since it and EPC were regarded as the same lesion termed intracystic papillary carcinoma until 2012. PDCIS is usually a small symptomless tumor that occurs in postmenopausal women. It is often first detected on routine screening mammography which shows microcalcifications (i.e. tiny deposits of calcium salts too small to be felt) or nodular densities. Rare cases of PDCIS have presented with a bloody nipple discharge. Males have presented with PDCIS: in one institutional review, 51 men aged 19 to 88 years were diagnosed with PDCIS; two of these men had gynecomastia. It is the most common type of ductal carcinoma in situ diagnosed in men. PDCIS tumors may occur alongside of (non-papillary) ductal carcinoma in situ or EPC tumors.
Pathology
The microscopic histopathology of typical PDCIS lesions (refer to adjacent high-power photomicrograph) prepared with a hematoxylin and eosin stain consists of mammary ducts that have papillary fronds (i.e. thin, finger-like or leaf-like structures) lined with one or several layers of neoplastic, columnar-shaped epithelial cells (i.e. tall, narrow cells with their nuclei close to the site of their ductal attachment). The fronds have branching fibrovascular cores. Epithelial cells lining the fronds' inner surfaces commonly form solid, cribriform (i.e. large nests of cells perforated by many rounded, variably sized spaces), or micro-papillary patterns. There may be a second population of epithelial cells lining the papillae that have abundant clear cytoplasm in addition to the usual neoplastic epithelial cells which line the papillae. These cells, which are not myoepithelial cells, have been termed globoid cells. They have eosinophilic cytoplasm (i.e. pink or red cytoplasm due to its uptake of eosin stain). PDCIS tumors with these cells have been termed dimorphic variants of PDCIS. Myoepithelial cells are typically present at the periphery of the fronds but absent within the involved ducts. The presence of a fibrous capsule and/or absence of peripherally located myoepithelial cells are strong indicators that the tumor is an ESP rather than a PDCIS. PDCIS tissues may also contain areas of "Comedo-type necrosis", i.e. areas where dead cells have accumulated. An Immunohistochemical study conducted in 2009 of 54 individuals diagnosed with PDCIS found that the tumor cells in 34, 31, and 35 cases, respectively, expressed the estrogen receptor, progesterone receptor, and HER2/neu protein. More resent reports find that these tumor cells strongly express the estrogen receptor in most cases and that PDCIS with tumor cells that do not express the estrogen receptor generally have a more malignant microscopic histopathology. While there are no specific gene alterations that have been repeatedly found in PDCIS tumor cells, the isolated cases in which they have been found were alterations similar to those occurring in low grade ductal carcinoma in situ tumors.
Treatment and prognosis PDCIS is managed primarily by surgical removal in the same manner as ductal carcinoma in situ tumors that have the same nuclear grade and estrogen receptor expression by their tumor cells (see treatment of ductal carcinoma in situ). (Nuclear grade describes how closely the nuclei of cancer cells look like the nuclei of normal breast cells; the higher the nuclear grade, the more abnormal appearing the nuclei are and the more aggressive the tumor cells tend to be.) PDCIS has an excellent prognosis with long-term survival rates similar to those for EPC.
Encapsulated papillary carcinoma
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