Howitt [93] described for the first time an epidemiologically rare but clinically relevant cohort composed by MMR deficient CCOCs, highlighting how they were associated with a significantly higher number of TILs and PD-1-positive TILs with respect to their microsatellite-stable counterpart and HGSOC; furthermore, MSI CCOCs homogenously expressed PD-L1 in the tumor cells and/or in the intraepithelial or peritumoral immune cells. Here, CD274 is linked to neoplasm.