An early study of PD-L1 expression in cancer found that high protein expression of PD-L1 on tumour cells from a mixed group of ovarian cancer histological subtypes, was associated with significantly poorer patient prognosis compared to low expression, and was inversely correlated with numbers of intraepithelial CD8+ tumour infiltrating lymphocytes (TILs) [31]. This evidence concerns the gene CD8A and neoplasm.