Recent studies have shown that the RFS and effectivenessof a targeted therapy with trastuzumab are reduced in HER2-positive BC patientswith intratumoral heterogeneity of the receptor expression compared to tumorswith homogeneous expression [36].Despite this, the relationship between HER2 heterogeneity and long-termtreatment outcomes in patients after surgery remains to be studied. The gene discussed is ERBB2; the disease is breast cancer.