The PI3K pathway is one of the most frequently altered networks in cancer [1], with mutation and/or amplification of the genes encoding RTKs such as HER2 (ERBB2) and FGFR1, the PI3K catalytic subunits p110α (PIK3CA) and p110β (PIK3CB), the PI3K regulatory subunit p85α (PIK3R1), the PI3K activator mutant K-RAS, the PI3K effectors AKT1, AKT2, PDK1, and loss of the lipid phosphatases PTEN and INPP4B. Here, PIK3CD is linked to cancer.