Apoptosis and cell proliferation in medullary carcinoma of the breast: A comparative study between medullary and non-medullary carcinoma using the TUNEL method and immunohistochemistry

Background and Objectives: Medullary carcinoma of the breast has generally been considered to result in better prognosis than ordinary invasive ductal carcinoma, which would seem to be discrepant when one considers its anapla stic histology and high mitotic rate. We attempted to elucidate the prognos tic implications of apoptosis and cell proliferation in medullary carcinoma of the breast. Methods: Formalin-fixed, paraffin-embedded specimens of 50 cases of typical medullary carcinoma (MC) of the breast and those of 50 control cases of no n-medullary invasive ductal carcinoma (N-MC), which were matched to the MC cases in both age and TNM classification, were investigated utilizing the t erminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) method and immunohistochemistry for p53, bcl-2, and Ki-67. Results: Mean values of the apoptotic index (AI), the proliferative index ( PI), and the ratio of AI to PI (AI/PI) were significantly higher in MC than in N-MC (P < 0.0001). MC exhibited significantly lower positivity for bcl- 2 than N-MC (P = 0.00003), while there was no significant difference in p53 positivity between MC and N-MC. Conclusions: A high frequency of apoptosis may be related to a favorable pr ognosis in MC, even though it demonstrates a high proliferative activity, e xhibiting a rapid cell turnover. J. Surg. Oncol. 1999;70:209-216. (C) 1999 Wiley-Liss, Inc.