Mononuclear cell infiltration in clear-cell renal cell carcinoma independently predicts patient survival

BACKGROUND. The impact of mononuclear cell infiltration on renal cell carcinoma (RCC) biology has been controversial, previously reported to be associated with either a favorable or unfavorable prognosis. The objective of the current study was to evaluate associations between mononuclear cell infiltration in routinely prepared paraffin-embedded specimens with survival in patients with clear-cell RCC. METHODS. A total of 306 patients were identified treated with nephrectomy for clear-cell RCC between 1990 and 1994. A single urologic pathologist, blinded to patient outcome, reviewed the specimens and quantified the extent of mononuclear cell infiltration as absent, focal, moderate, or marked. Cancer-specific survival was estimated using the Kaplan-Meier method. Associations of mononuclear cell infiltration with death from RCC were assessed using Cox proportional hazards regression models. RESULTS. At last follow-up, 173 of the 306 patients studied had died, including 96 patients who died from RCC. Mononuclear cell infiltration was absent in 165 (54%), focal in 70 (23%), moderate in 53 (17%), and marked in 18 (6%). Univariately, patients with specimens that had mononuclear cell infiltration were over 2 times more likely to die from RCC compared with patients whose specimens exhibited no mononuclear cell infiltration (risk ratio, 2.63; P<.001). After adjusting for the Mayo Clinic SSIGN (stage, size, grade, and necrosis) score, patients with specimens that had mononuclear cell infiltration exhibited a significantly increased likelihood of dying from RCC compared with patients whose specimens had no mononuclear cell infiltration (risk ratio, 1.61; P = .028). CONCLUSIONS. Mononuclear cell infiltration is associated with death from RCC even after multivariate adjustment. Routine documentation of mononuclear cell infiltration is recommended during the pathologic assessment of RCC.