PD-L1 expression on tumor cells, described in about 70% of cases, has recently been identified as a poor prognostic factor in GIST and is inversely correlated with the presence of CD8+ T-lymphocytes (56, 57), suggesting a real lymphocyte anergy induced by PD-L1 expression on tumor cells. The gene discussed is CD8A; the disease is gastrointestinal stromal tumor.