Male breast cancer: immunohistochemical subtypes and clinical outcome characterization

The aim of this study was to assess the molecular subtype profiles of male breast cancer (MBC) and subsequent clinical outcome using a validated 6-marker immunohistochemical panel.

A total of 43 cases of MBC were examined retrospectively using a semiquantitative immunohistochemical analysis of estrogen receptor (ER), progesterone receptor (PR), Ki-67, human epidermal growth factor receptor 2 (Her2), epidermal growth factor receptor and cytokeratin 5/6. Patients were classified into the following categories: luminal A, luminal B, Her2-positive or basal-like subtypes.

The median age of patients was 63 years (r: 32-89). The predominant histology was invasive ductal carcinoma (91%). Only 1 patient had advanced breast cancer at diagnosis. Ninety-three percent were ER-positive and 84% were PR-positive. Two patients had tumors that were ER- and PR-negative. The distribution of tumor molecular subtypes was 19 (44%) luminal A, 22 (51%) luminal B and 2 (5%) basal-like. The Her2-positive tumor subtype was not identified. The clinicopathological characteristics did not differ significantly between tumor subtypes A and B. There were no significant differences in 6-year disease-free survival (74 vs. 82%, p = 0.77) or overall survival (74 vs. 82%, p = 0.69) between luminal A and luminal B subtypes, respectively.

The most common subtypes in our cohort of MBC were luminal B followed by luminal A, and no differences were found between both tumor subtypes in terms of clinicopathologic characteristics and patient outcome.