Rosen's Breast Pathology, 4e

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Chapter 11

FIG. 11.66.  DCIS, basement membrane and microinvasion . A: DCIS, comedo type with calcification ( right ) and micro- invasive carcinoma ( left ). B: The immunostain for laminin shows a multilayered basement membrane of variable thickness. The basement membrane is incomplete in the lower left region, which is adjacent to the microinvasive carcinoma shown in a parallel section in (A) . C: The immu- nostain for CD34 shows maximal periductal neovascular- ity on the left in the region of microinvasion. The choice of an immunohistochemical marker for myoep- ithelial cells “should be dependent on a combination of factors, including published evidence of its diagnostic utility, its avail- ability, performance characteristics that have been achieved in a given laboratory, and the specific diagnostic criteria.” 293 The markers or myoepithelium that are commonly de- tected by immunostain in diagnostic pathology include the following, in alphabetical order: Calponin inhibits ATPase activity of myosin in mammary myoepithelial cells, wherein it is highly sensitive but not specific as it is reactive in a subset ofmyofibroblasts. CD10 is an endopeptide that is relatively sensitive for the detection of myoepithelial cells. CKs 5, 10, 14, and 17 are expressed in myoepithelial cells. CK-K903 (34βE12) is not specific formyoepithelial cells, but is useful for the diagnosis of metaplastic spindle cell carcinoma. H-caldesmon is an SMA-binding protein expressed in myoepithelial cells, mainly around ducts. Maspin is a serine protease inhibitor, which is expressed in the cytoplasm and nuclei of myoepithelial cells. P-cadherin is a cell adhesion molecule with high sen- sitivity for myoepithelial cells, which is not reactive in myofibroblasts. p63 , a p53 homolog, is highly sensitive for myoepithelial cells and is expressed in nuclei thereof. S-100 protein can be identified in a proportion of benign and malignant mammary epithelial cells, as well as myoepi- thelial cells, and therefore is not useful.

than 1.0 cm in diameter. 289–291 Microinvasive carcinoma is a subcategory of minimally invasive carcinoma. Microinvasion is defined as an invasive focus 1 mm or less in greatest extent. A controversial aspect of the histologic diagnosis of mi- croinvasion relates to the interpretation of ducts that have poorly defined walls with an indistinct basement membrane. In such regions, the neoplastic epithelium may appear to protrude from the duct wall, seeming to come in direct con- tact with the stroma although it remains connected with the intraductal neoplasm 292 (Figs. 11.29 and 11.67). This find- ing often elicits diagnostic uncertainty reflected in such ca- veats as “suspect microinvasion” or “microinvasion cannot be ruled out.” Retrospective studies have given no indication that these ambiguous findings are associated with an appre- ciable risk of systemic metastases, but they may account for some instances in which micrometastases have been detected in sentinel lymph nodes (SLNs) from patients with DCIS. To qualify for the term microinvasion , the cells deemed to be invasive must be distributed in a fashion that does not represent tangential sectioning of a duct or a lobular gland with DCIS (Figs. 11.67 and 11.68). Tangentially sectioned in situ carcinoma that simulates microinvasion usually results in compact groups of tumor cells that have a smooth border surrounded by a circumferential layer of cells of stromal and/ or myoepithelial origin. These “organoid” foci are distributed in the specialized periductal or intralobular stroma. Immu- nostains may be helpful in resolving the problem.