ERBB2 and breast carcinoma: We next examined PKCα expression stratified by breast cancer subtype categorized as luminal A (ERα+/PR+/Her2−), luminal B (ERα+/PR+/Her2+), HER2 (ERα−/PR−/Her2+), and triple-negative breast cancer (TNBC, ERα−/PR−/Her2−) based solely on receptor expression as determined by IHC.