Immunohistochemical expression of metallothionein in invasive breast cancer in relation to proliferative activity, histology and prognosis.

Immunohistochemically detected metallothionein expression [MT(+)] was shown to be related to aggressive behavior of the invasive ductal carcinoma of the breast. In this study, MT expression was examined immunohistochemically in 92 cases of invasive breast carcinoma and compared with immunohistochemically demonstrated estrogen receptor (ER), c-erbB-2, Ki-67 status and clinicopathological characteristics. Of the 92 cases examined, 27.1% (25 cases) were MT(+), and high percentages of the solid tubular subtype of invasive ductal carcinoma (47%), medullary carcinoma (80%), and carcinomas with spindle cell metaplasia (100%) were positive for MT. MT(+) carcinomas showed tendency to have highly atypical nuclei, and nuclear staining for Ki-67 antigen was found in a higher percentage of cases than in MT(-) carcinomas. An inverse relationship between MT(+) and ER immunoreactivity was observed. MT expression was not associated with age distribution, menopausal status, tumor size or lymph node metastasis. The overall survival rate in MT(+) cases was worse than in those negative for MT, but no significant association was found. MT(+) was not associated with poor prognosis in total, estrogen receptor-negative or node-negative tumors. These findings suggest that MT expression in breast cancer cells is related to cell-proliferative activity, and that dedifferentiation of carcinoma cells may play a role in induction of MT expression.