Abstract
Breast cancer (BC) is classified based on the expression of histopathological markers, namely, estrogen receptor (ER), progesterone receptor (PgR), and human epidermal growth factor receptor 2 (HER2). Carcinomas with apocrine differentiation (CAD) are classified based on morphology. Androgen receptor (AR) is highly expressed in CAD; however, no study has comprehensively examined AR-related proteins in CAD. Therefore, we examined the expression of AR-related proteins and AR, compared protein expression patterns between morphologically identified CAD and other BC subtypes, and investigated CAD characteristics. We performed immunohistochemistry for AR and various AR-related proteins in 66 invasive ductal carcinoma (32 ER+/PgR+/HER2-, 8 ER+/PgR+/HER2+, 12 ER-/PgR-/HER2+, and 14 ER-/PgR-/HER2- [triple-negative breast cancer)), 21 invasive lobular carcinoma, and 27 CAD cases. In the CAD group, all cases were AR-positive; some AR-related proteins were highly expressed. Nuclear phosphorylated-mammalian target of rapamycin was highly expressed in CAD cases compared with that in other BC groups, with a 33.3% sensitivity and 97.7% specificity. AR-expressing CAD cases exhibited high expression of other AR-related proteins. Specifically, the combination of AR+, GCDFP15+, and ER - or AR+, FOXA1+, and ER - may be useful for the diagnosis and treatment of AR-positive BC and CAD. These results may assist in androgen-related molecular targeted therapy research.