PIK3CA and osteosarcoma: Aberrant activation of the PI3K/AKT pathway has been observed in almost all types of tumor cells (37–39), such as ovarian cancer (40, 41), lung cancer (42, 43), gastric cancer (44, 45), pancreatic cancer (46, 47), breast cancer (48, 49), hepatocellular carcinoma (50, 51), lymphoma (52, 53), osteosarcoma (54) and so on.