CD274 and ovarian carcinoma: The presence of abundant reactive cells in Reed Sternberg cells and tumor microenvironment is its significant clinicopathological feature, and most Reed Sternberg cells have the expression of programmed cell death ligand 1 (PD-L1), which may be related to tumor cells escaping from the immune response of the body.[1] PD-L1 is highly expressed in melanoma,[2] gastric cancer,[3] liver cancer,[4] ovarian cancer,[5] and other tumors.