PIK3CA and breast cancer: From breast cancer actionability, PIK3CA (ESCAT Tier IA) was reported in 39.4% (n = 97), AKT1 mutation (ESCAT Tier IIB) in 45.9% (n = 113), and ERBB2 mutation (ESCAT Tier IIB) in 17.1% (n = 42) of early-stage Taiwanese breast cancers (Table 3).