ERBB2 and neoplasm: Regarding other sources of intratumoral heterogeneity in particular subtypes, TN and HER2+ have been associated with a more immunogenic tumor microenvironment, with a higher presence of immune cells such as tumor-infiltrating lymphocytes (TILs) [7] and the activation of multiple signaling pathways as programmed death 1/programmed death ligand 1 (PD-1/PD-L1) [8,9].