CD4 and neoplasm: Mis-match deficient (MMR) microsatellite instability (MSI)-high OCCCs have been shown to harbor significantly higher CD8+ tumour-infiltrating lymphocytes (TILs), higher CD8 +/CD4 + ratios and higher PD1+ TILs compared to microsatellite-stable (MSS) OCCCs [22], and although MMR deficiency is only seen in around 10% of OCCC, some degree of tumoural and stromal PD-L1 expression has been reported in around 74% of OCCC [23], suggesting that additional subsets of OCCC show immunogenicity [20].