Cytokeratin 8 immunostaining pattern and E-cadherin expression distinguish lobular from ductal breast carcinoma.

Immunohistochemistry using antibodies to cytokeratin 8 can serve as a valuable diagnostic tool for the differentiation of lobular from ductal carcinomas of the breast. In contrast with ductal carcinomas, which exhibit a peripheral-predominant immunostaining pattern, adjacent tumor cells “molding” to each other, lobular carcinomas exhibit a ring-like perinuclear immunostaining pattern, creating a “bag of marbles” appearance with neighboring tumor cells. This immunostaining pattern is stable even in the tumors that otherwise do not exhibit characteristic histomorphologic features (ie, solid or pleomorphic type of a lobular carcinoma) and tumors that mimic growth patterns characteristic of the…