Expression of bcl-2 by breast cancer: a possible diagnostic application

Expression of bcl-2 is most commonly associated with the t(14;18) translocation present in most folicular lymphomas (1). More recently, bcl-2 oncoprotein has been identified in normal tissues and in nonhematologic malignancies. In this study, we investigate the use of bcl-2 as a marker to distinguish metastatic breast carcinoma from primary lung and gastric cancers, and we evaluate the role of bcl-2 as an independent prognostic factor in breast carcinoma and its relationship to other breast cancer markers. bcl-2 immunostains were done on 371 adenocarcinomas of the breast, lung, and stomach. Additionally, 231 samples of metastases from patients with breast or gastric cancer were evaluated for bcl-2 expression. All breast cancer tissue samples had immunohistochemical data on expression of estrogen and progesterone receptors, p53, neu/cerb2, and MIB-1. A large proportion (79.3%) of invasive breast carcinomas expressed bcl-2, whereas only 5.6% and 8.3% of pulmonary and gastric carcinomas did. Moreover, staining was moderate to intense in 70.2% of the breast cancers, compared with only one specimen of lung carcinoma (1.9%) and gastric carcinoma (0.9%) that showed moderate staining. There was agreement of bcl-2 expression between primary and metastatic sites in all specimens except one. Expression of bcl-2 in breast adenocarcinomas was significantly associated with hormone receptor positivity and low histologic grade. Nonetheless, 20.6% of bcl-2-positive specimens were estrogen receptor negative and 24.2% of bcl-2-positive specimens were progesterone receptor negative. Neither the presence nor the absence of bcl-2 expression significantly predicted disease-free survival or overall survival in patients with breast cancer. We conclude that adenocarcinomas with intense bcl-2 staining are more likely to be of breast than of pulmonary or gastric origin. We recommend the addition of bcl-2 to a panel of antibodies (estrogen receptor, GCDFP-15, and S100) that might contribute to the identification of a larger proportion of metastatic breast carcinomas, because almost one-half of the estrogen-receptor negative cancers were bcl-2 positive.