PIK3CB and cancer: The molecular alterations leading to activation of the PI3K pathway in cancer are varied and include mutations in the genes encoding the PI3K alpha (PIK3CA) and beta (PIK3CB) catalytic subunits, AKT1 mutations, and loss of expression of the phosphatidylinositol-3,4,5 trisphosphate (PIP3) phosphatases PTEN and INPP4B. Mutations in PIK3CA and AKT1 are relatively uncommon in triple-negative breast cancer [7]; however, loss of PTEN and/or INPP4B has been reported in 30–60% of basal-like tumors [7–9].