The
cadherins are homotypic adhesion
proteins that are important in cell sorting during organogenesis. Classical
cadherins include several different types that show tissue-specific expression. Cell lineage-specific expression of different
cadherin subtypes can differentiate morphologically similar but 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 carcinomas, 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 epithelial component but not the sarcomatous areas of 2 of 2 cases of
carcinosarcomas.
E-cadherin was not detected in the stromal
tumors (phyllodes, periductal stromal
tumor).
N-cadherin was most frequently expressed in sarcomatoid metaplastic
carcinomas (5 of 5), and variably in other
tumors, including the sarcomatous area of
carcinosarcoma (1 of 2), and 6 of 22
medullary carcinomas.
P-cadherin was frequently identified in
medullary carcinomas (20 of 22), in 5 of 5 metaplastic
carcinomas, and in the proliferating stroma and benign 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 classification and diagnosis.