ERBB2 and breast cancer: PAM50 is a well-known set of 50 genes that were found and identified by analyzing many genome-wide expression profiles of breast cancer patients (mainly by Charles M. Perou and collaborators), and included in a classifier of breast cancer tumors (i.e. PAM50) that defined five gene expression-based intrinsic subtypes: Luminal A, Luminal B, HER2-enriched, Basal- and Normal-like (Parker et al., 2009).