KMT2C and breast cancer: Table 1 summarizes the most commonly mutated genes (27, 44). Copy number alterations have been observed in PIK3CA, ERBB2, TP53, MAP2K4, MLL3, CDKN2A, PTEN, and RB1 (44). Approximately 35-40% of primary breast cancers harbor mutations in TP53 and PIK3CA, as well as amplification of ERBB2, FGFR1, and CCND (~15%), and mutations in MUC16, AHNAK2, SYNE1, KMT2C, AKT1, and GATA3 genes (10%) (25, 45). In 2012, the Cancer Genome Atlas Network (CGAN) identified novel significantly mutated genes (SMGs), including TBX3, RUNX1, CBFB, AFF2, PIK3R1, PTPN22, PTPRD, NF1, SF3B1, and CCND3 (26).