EMA: a differentiation antigen related to node metastatic capacity of breast carcinomas.

Epithelial membrane antigen (EMA), also known as MUC1, is a mucinous glycoprotein fixed to the luminal domain of the epithelial cell membrane of normal breast ducts. However, in breast cancer cells, it is usually dispersed in the cytoplasm. EMA staining patterns of 330 breast carcinomas were examined, and three groups formed: lineal (16%), cytoplasmic (75%), and negative (9%). Although these patterns were somewhat related to histological cancer types, this was not statistically significant. However, EMA showed statistically significant univariate relationships to tumor grade, tumor size, estrogen and progesterone receptors, and nodal stage. Logistic regression analysis showed that among these variables, all of which were univariately related to node metastasis, only tumor size and EMA were independent nodal stage predictors. A combined analysis of these two factors revealed that the statistical probability of a tumor metastasizing to four or more nodes increased in each tumor size group from 0.9% to 12% for pT1, from 2% to 29% for pT2 and from 10% to 63% for pT3, depending on the EMA staining. The tumors showing a lineal pattern were the least metastasizing, while the EMA-negative tumors were the most. After recognizing these relationships between EMA staining patterns and other well-known differentiation markers and the lymph node metastatic capacity of carcinomas, and considering the results obtained by others on survival, one might conclude that EMA is both a differentiation marker and a histological prognostic factor.