Objective: investigate the expression of apoptosis markers in metastatic breast cancer. Methodology: A total of 25 paraffin samples of breast carcinomas and 25 samples of cell block of malignant pleural effusion were evaluated, for the same patients. The sections were subjected to immunohistochemistry using antibodies markers of apoptosis, Bcl-2 (anti-apoptotic) and Bax (pro-apoptotic). Results: It was observed that 100% (n = 25) of primary tumor samples and 96% (n = 24) samples of malignant pleural effusion were positive for marker Bax. There was a significant association between increased Bcl-2 expression in breast tumor and the consequent decrease of Bax expression in malignant pleural effusion (p = 0.045). Bax protein was significantly increased in cases where there is low spread of breast tumors (p = 0.040). The outcome of death was observed in 72% (n = 18) case. Correlation was found between the pro-apoptotic protein expression and decreased survival time from diagnosis of pleural effusion and death (p = 0.041). Conclusion: It is observed that there is a relationship between increased anti-apoptotic marker expression in the primary tumor and the consequent reduction of the pro-apoptotic marker in metastasis, and the marker of apoptotic promotion (Bax), is associated with better outcomes and increased survival of patients with metastatic breast cancer. Breast cancer is currently the leading cause of cancer death in women. Studies of genes involved in the apoptotic process aimed at broadening the knowledge of humoral progression, and establish new prognostic markers for these patients.