Sue-A-Quan R, Patel PG, Shakfa N, et al. - Researchers herein describe the pretreatment tumour immune landscape of clear cell carcinoma of the ovary (CCOC). They employed multiplex immunohistochemistry to assess the density of CD3+, FoxP3+, CD8+ T cells, CD20+ B cells as well as expression of PD-1, PD-L1 and IDO1 immune checkpoints in a cohort of 162 CCOC tumour specimens on a tissue microarray. They found that increased infiltration of CD3+ CD8- (helper T) cells, CD8+ (cytotoxic T) cells, and CD68+ macrophages was significantly related to a shorter disease-free survival, recurrence-free survival and overall survival. Essentially, better clinical results were obtained in relation to higher expression of PD-L1 and IDO-1 immune checkpoints. These observations are fundamental for the future developments in immunotherapeutic management of CCOC.