Male breast cancer according to tumor subtype and race: a population-based study

Breast cancer occurs rarely in men. To the authors' knowledge, no population-based estimates of the incidence of human epidermal growth factor receptor 2 (HER2)-positive breast cancer or of the distribution of breast cancer subtypes among male breast cancer patients have been published to date. Therefore, the objective of the current study was to explore breast tumor subtype distribution by race/ethnicity among men in the large, ethnically diverse population of California.

This study included men who were diagnosed with invasive breast cancer between 2005 and 2009 with known estrogen receptor (ER) and progesterone receptor (PR) (together, hormone receptor [HR]) status and HER2 status reported to the California Cancer Registry. Among the men with HR-positive tumors, survival probabilities between groups were compared using log-rank tests.

Six hundred six patients were included. The median age at diagnosis was 68 years. Four hundred ninety-four men (81.5%) had HR-positive tumors (defined as ER-positive and/or PR-positive and HER2-negative). Ninety men (14.9%) had HER2-positive tumors, and 22 (3.6%) had triple receptor-negative (TN) tumors. Among the patients with HR-positive tumors, non-Hispanic black men and Hispanic men were more likely to have PR-negative tumors than non-Hispanic white men. No statistically significant differences in survival were observed according to tumor subtype (P = .08). Differences in survival according to race/ethnicity were observed among all patients (P = .087) and among those with HR-positive tumors (P = .0170), and non-Hispanic black men had poorer outcomes.

In this large, representative cohort of men with breast cancer, the distribution of tumor subtypes was different from that reported for women and varied by patient race/ethnicity. Non-Hispanic black men were more likely to have TN tumors and ER-positive/PR-negative tumors than white men.