Rosen's Breast Pathology, 4e

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Chapter 11

FIG. 11.72.  DCIS with vascular tumor emboli. A,B: After a needle core biopsy revealed DCIS, this patient underwent excisional biopsy. The specimen contained cribriform DCIS shown here with carcinoma cells in an adjacent vascular channel ( arrow ). C: Isolated cytokeratin (AE1/3) positive cells were present in subcapsular sinuses of the SLNs. concluded that “since invasive breast carcinoma may mimic intraductal growth, some cases of breast cancer diagnosed histologically as DCIS may, in reality, be invasive.” This phe- nomenon may be responsible for the rare patient found to have axillary nodal metastases, especially as a result of SLN mapping, when the breast appears to be the site of DCIS with no demonstrable invasion. The difficulties raised by the structural similarities of in situ and invasive duct carcinoma are complicated by the re- sults of studies that have demonstrated the presence of base- ment membrane components around groups of invasive carcinoma cells (Fig. 11.74). Arihiro et al. 305 found immuno- reactivity for laminin at sites of invasive carcinoma in 54% of 71 carcinomas. The presence of laminin was associated with a greater degree of tubule formation. These findings correlate with data obtained by Nadji et al. 306 as significantly related to low histologic and nuclear grade. In light of the foregoing discussion, it is evident that there are instances in which the presence or absence of micro- invasion can be difficult to determine with certainty, even with the immunohistochemical reagents currently avail- able. Some guidelines can be suggested based on experience: 1. Thepresenceofmyoepithelial cells at theperimeter of neo- plastic glands is the most convincing evidence of DCIS, especially if demonstrated with the p63 immunostain.

assume a growth pattern that simulates DCIS (Fig. 11.73). This occurrence is most easily appreciated in metastatic de- posits at sites outside the breast such as the ALNs and less frequently in visceral metastases. The phenomenon was de- scribed by Cowen 302 in 1980 and in a later report, Cowen and Bates 303 reported finding metastatic carcinoma with a DCIS-like appearance in lymph nodes from 35 of 391 pa- tients (9%) with axillary metastases. In two of these cases, no intraductal component was found in the primary tumor, but in the others the “pseudointraductal” carcinoma in metasta- ses resembled DCIS in the primary lesion. Barsky et al. 304 reported finding DCIS-like metastases in ALNs from 21% of 200 cases. These foci were termed “re- vertant” DCIS to reflect the hypothesis that this phenom- enon is a manifestation of a condition in which metastatic potential is inhibited or reversed by local factors. The au- thors observed complete concordance between primary and “revertant” DCIS with respect to architectural pat- tern, nuclear size determined by digital image analysis, and the expression of the prognostic markers p53, HER2, and Ki67. “Revertant” DCIS featured circumferential basement membranes demonstrated by immunoreactivity for laminin and type IV collagen, but lacked myoepithelial cells. The capacity of invasive carcinoma to assume an appearance that resembles its in situ counterpart could complicate the diagnosis of microinvasive carcinoma. Cowen and Bates 303