Cytokeratin 8 immunostaining pattern and E-cadherin expression distinguishlobular from ductal breast carcinoma

Immunohistochemistry using antibodies to cytokeratin 8 can serve as a valua ble diagnostic tool for the differentiation of lobular from ductal carcinom as of the breast. In contrast with ductal carcinomas, which exhibit a perip heral-predominant immunostaining pattern, adjacent tumor cells "molding" to each other lobular carcinomas exhibit a ring-like perinuclear immunostaini ng pattern, creating a "bag of marbles" appearance with neighboring tumor c ells. This immunostaining pattern is stable even in the tumors that otherwi se do not exhibit characteristic histomorphologic features (ie, solid or pl eomorphic type of a lobular carcinoma) and tumors that mimic growth pattern s characteristic of the respective other turner type (ie, targetoid or sing le-file growth pattern in a ductal carcinoma). Furthermore, we demonstrate that ductal carcinomas express E-cadherin in a similar peripheral-predomina nt immunostaining pattern (33/33 cases), while all 15 lobular carcinomas we re negative for E-cadherin, suggesting a role for E-cadherin in the archite ctural organization of the cytoskeletal scaffolding within the tumor cells.