Basal cytokeratin expression in relation to biological factors in breast cancer

The objective of this study was to determine the predictive impact of several established tumor biological markers and clinicopathological findings for basal-like carcinoma. Expression was determined by immunohistochemistry using antibodies to cytokeratins 5/6, 14, and 17, and the cases were divided into basal-like carcinoma and non basal-like carcinoma. These subgroups were compared in terms of biological markers (HER2, estrogen receptor, progesterone receptor, Ki-67, P-53, and P-glycoprotein) and clinicopathological behavior. Of the 49 basal-like carcinoma cases, 25(51.0%) were P-53–positive, whereas 100 (35.9%) of the 278 non basal-like carcinoma cases were P-53–positive. A high ratio of nuclear Ki-67 expression was detected in 39 (79.6%) of 49 basal-like carcinoma cases and was significantly more common than in non basal-like carcinoma cases (81/278, 29.1%). P-glycoprotein expression was identified in 29 (59.2%) of 49 basal-like carcinomas but only 85 (30.6%) of 278 non basal-like carcinomas. We observed high levels of P-53, Ki-67, and P-glycoprotein, with the reduction or loss of estrogen receptor, progesterone receptor, and HER2 being more obvious, in basal-like carcinomas than in non basal-like carcinomas. Our findings provide further evidence that basal-like carcinoma has different mechanisms of histogenesis.