Androgen receptor expression shows distinctive significance in ER positive and negative breast cancers

Androgen receptor (AR), a nuclear steroid hormone receptor, is differentially expressed in breast cancer subgroups with distinct clinical implications.

To investigate the clinical significance of AR in breast cancers more precisely, the expression of AR in a large cohort of breast cancer was correlated with clinicopathological features, biomarker expression, and patients' survival according to different molecular groupings in this study.

Higher AR expression was found in ER+ (57.8 %) than in ER- (24.7 %) cancers. In the ER+ cancers, AR expression was associated with favorable clinicopathological features, including lower grade (p < .001), lower pT stage (p < .001), and positivity for PR (p < .001). It was an independent prognostic factor for longer disease-free survival, mainly in the HER2+ luminal B cancers (hazard ratio [HR] = 0.251, 95 % CI 0.065-0.972, p = .045). In ER- cancers, AR expression was associated with features distinct from basal-like breast cancer, and such features were found in molecular apocrine (MA) cancers. AR correlated with presence of extensive in situ component (p = .006) and apocrine phenotype (p < .001), HER2 (p = .026), and EGFR (p = .048), but negatively with c-kit (p = .041), CK5/6 (p < .001), CK14 (p = .002), and αB-crystallin (p = .038). However, AR expression was found only in 37.8 % of immunohistochemically defined MA. Of note, AR-MA appeared to have a trend of worse overall survival than AR+MA.

AR expression was different in ER+ and ER- cancers and had different clinical implications. AR alone may not be a good marker for MA subtype. Its expression in MA may have substantial prognostic implication and as such warrants further validation.