PIK3CB and gastrointestinal stromal tumor: As the most common mesenchymal tumor of the digestive system, gastrointestinal stromal tumors (GISTs) mainly harbor mutually exclusive KIT or PDGFRA mutations, which lead to constitutive activation of the encoded receptor tyrosine kinase (RTK) and activation of downstream pathways including PI3K/AKT pathway [132, 133].