Nakanishi H, et al. - Considering the close association of immune system with malignant behavior in renal cell carcinoma (RCC), researchers investigated the clinical significance of densities of CD57+ cells, CD68+ cells, and mast cells, and their ratios in patients with clear cell RCC. Findings revealed that in RCC tissues, CD57+ cell density acted as an anti-cancer factor. Furthermore, important roles of CD68+ cell and mast cell were suggested in tumor progression in RCC. CD68+ cell/CD57+ cell ratio seemed to be a useful predictor for prognosis in RCC patients as this ratio reflected the status of cancer cell proliferation, apoptosis, and angiogenesis.