Male breast cancer: correlation between immunohistochemical subtyping and PAM50 intrinsic subtypes.

1585Background: Male breast cancer (MBC) is a rare disease that is still poorly understood. It is mainly classified by immunohistochemistry (IHQ) as a luminal disease. In this study, we use for the first time the PAM50 signature to unravel the molecular genetic heterogeneity in MBC. Methods: We collected surgical specimens of invasive MBC from four different Spanish pathology laboratories. IHQ staining for estrogen receptor (ER), progesterone receptor (PR), androgen receptor (AR), human epidermal growth factor receptor 2 (HER2), cytokeratin 5/6 (CK5/6), epidermal growth factor receptor (EGFR) and Ki-67 was performed on tissue microarrays composed of 3 cores sized 0.6 mm per case by standard methods. Breast cancer molecular subtypes were classified according to Cheang et al. (2009). Gene-expression profiling was performed on a research-use-only (RUO) nCounter Analysis System using the RUO PAM50 assay analyzed with the Prosigna algorithm. We explored the association of IHQ and PAM50 subtypes using Fisher’s ...