Immunohistochemical investigation of CD34 antigen in male breast carcinoma.

A total of 30 archival cases of male breast carcinoma were studied immunohistochemically for the expression of CD34 antigen. An obvious CD34 staining was found in three cases. By adding the original CD34-positive case, recently published as unique CD34-stained male breast carcinoma, the number of positive cases comes to four. This case was classified as an invasive papillary carcinoma of solid conformation, whereas the three other cases were invasive ductal carcinomas, not otherwise specified. The aim of this study is to establish whether the CD34 positivity, observed in the case of papillary subtype, was a case-specific finding. CD34 expression in the male breast carcinoma, according to our findings, seems to be neither a feature presented exclusively by a singular case nor a specific immunophenotype characterising a special type. The presence or preservation of CD34 antigen in four totally male breast carcinomas may be considered as a novel finding that supports a relationship between these tumours and the progenitor CD34-positive stem cells, committed to the organogenesis of mammary gland. In this context we hypothesise an origin of male breast carcinoma from the stem cells expressing or not the CD34 antigen according to their stage of differentiation.