Sarcoid-like granulomas in renal cell carcinoma: The Houston Methodist Hospital experience

Sarcoid-like (SL) granulomas have been previously described in association with malignant tumors. These granulomas appear to be tumor-related but are not indicative of systemic sarcoidosis, and hence are referred to as SL reactions. These SL reactions can be seen within the primary tumor, its vicinity, or in uninvolved sites such as the spleen, bone marrow, skin, and/or regional lymph nodes draining the tumor. It is a widely held view that SL granulomas are caused by soluble antigenic factors, shed by tumor cells or released due to tumor necrosis. SL reactions reported in Hodgkin lymphoma have been associated with a better prognosis. SL granulomas are thought to play an important role in the host's defenses against metastatic extension. SL granulomas have been reported in approximately 4.4% of carcinomas. Isolated cases of renal cell carcinoma (RCC) with SL granulomas have been reported with questionable prognostic significance. We identified 11 cases of RCCs with SL granulomas. Interestingly, all cases had abundant clear cell cytoplasm (10 clear cell RCC cases and 1 clear cell papillary RCC). We propose that this clear, abundant cytoplasm of the tumor cells with high content of glycogen and lipids may trigger granuloma formation akin to that seen in seminomas with SL granulomas. To date, this is the largest case series of RCCs with SL granulomas.