Prognostic significance of tumor subtypes in male breast cancer: a population-based study

Substantial controversy exists about the prognostic role of tumor subtypes in male breast cancer (MaBC). The aim of this study was to analyze the characteristics of each tumor subtype in MaBC and its association with prognosis compared with other factors. We evaluated MaBC patients between 2010 and 2012 with known estrogen receptor, progesterone receptor [together hormone receptor (HR)] status, and human epidermal growth factor receptor 2 (HER2) status reported to the Surveillance, Epidemiology, and End Results program. Patients were classified as: HR-positive/HER2-negative, HR-positive/HER2-positive, HR-negative/HER2-positive, and triple-negative (TN). Univariate and multivariate analyses determined the effect of each variable on overall survival (OS). We included 960 patients. Patient distribution was 84.9 % HR-positive/HER2-negative, 11.6 % HR-positive/HER2-positive, 0.6 % HR-negative/HER2-positive, and 2.9 % TN. TN patients were younger, had higher grade, presented with more advanced stage, were more likely to have mastectomy, and to die of breast cancer (all P < 0.05). Univariate analysis showed that HER2 positivity was associated with shorter OS (hazard ratio 1.90, P = 0.031) and TN patients had worse prognosis (hazard ratio 5.10, P = 0.0004). In multivariate analysis, older patients (hazard ratio 3.10, P = 0.032), those with stage IV (hazard ratio 16.27, P < 0.001) and those with TN tumors (hazard ratio 4.61, P = 0.002) had significantly worse OS. We observed significant differences in patient characteristics according to tumor subtype. HER2-positive and TN represented a small proportion of cases. In addition to age and stage, tumor subtype has clear influence on OS in MaBC.