Distinct cadherin profiles in special variant carcinomas and other tumors of the breast

The cadherins are homotypic adhesion proteins that are important in cell so rting during organogenesis. Classical cadherins include several different t ypes that show tissue-specific expression. Cell lineage-specific expression of different cadherin subtypes can differentiate morphologically similar b ut histogenetically distinct tumors. We examined by immunohistochemistry in paraffin sections, the expression of E- (epithelial), N- (neural), and P- (placental) cadherin in 36 unusual tumors of the breast (22 medullary carci nomas, 5 metaplastic carcinomas, 2 carcinosarcomas, 4 phyllodes tumors, and 3 periductal stromal tumors). All carcinomas stain with E-cadherin (22 of 22 medullary and 5 of 5 metaplastic). E-cadherin also stained the epithelia l component but not the sarcomatous areas of 2 of 2 cases of carcinosarcoma s. E-cadherin was not detected in the stromal tumors (phyllodes, periductal stromal tumor). N-cadherin was most frequently expressed in sarcomatoid me taplastic carcinomas (5 of 5), and variably in other tumors, including the sarcomatous area of carcinosarcoma (1 of 2), and 6 of 22 medullary carcinom as. P-cadherin was frequently identified in medullary carcinomas (20 of 22) , in 5 of 5 metaplastic carcinomas, and in the proliferating stroma and ben ign epithelium of 3 of 3 periductal stromal, but not in phyllodes tumors (0 of 4). All sarcomatoid metaplastic carcinomas co-expressed all 3 classical cadherins. Our results show that these breast tumors have unique patterns of cadherin expression suggesting different histogenetic origin or lines of differentiation. The cadherin profiles in these tumors may be useful for c lassification and diagnosis, HUM PATHOL 30:1035-1039. Copyright (C) 1999 by W.B. Saunders Company.