Additionally, somatic mutation analysis in 34 premenopausal breast cancer FFPE samples deriving from our cohort, revealed that 71.4% (25/34) of tested patients were carriers of somatic variations in tumor suppressor genes (TP53, NF1, RB), genes involved in DNA repair (BRCA1, BRCA2, ATM, RAD50), in cell proliferation (PTEN, PIK3CA, FGFR3, AKT1, ROS1, ERBB2, NOTCH1), and in cell adhesion (CTNNB1). This evidence concerns the gene ERBB2 and breast cancer.