CD8A and ovarian cancer: The unique peritoneal metastasis microenvironment of ovarian cancer is composed of tumor cells, immune cells including CD4+ and CD8+ T cells, tumor-associated macrophages (TAMs), natural killer cells (NK cells), dentritic cells (DCs), and myeloid-derived suppressor cells (MDSCs), as well as stromal cells including adipocytes, fibroblasts, human peritoneal mesothelial cells, and endothelial cells.