CD274 and gastrointestinal stromal tumor: Because recent evidence revealed that PD-1 and PD-L1 levels in several tumors may be relevant prognostic factors [17,28,29,30], our investigation aimed to discover if soluble forms of immunomodulatory molecules, such as PD-1, PD-L1, BTN3A1, and pan-BTN3As, may be helpful in predicting the survival of metastatic GIST (mGIST) patients, in order to obtain significant information about the clinical evolution of disease.