Primary carcinoid of the kidney: light and electron microscopic study.

A case of an asymptomatic primary renal carcinoid tumor in a 61-year-old male is presented. The tumor was large with extensive hemorrhagic necrosis. Metastases were present in para-aortic lymph nodes. Ultrastructurally, dense core granules and masses of cytoplasmic filaments, including tonofilaments, were seen. The granules were faintly argyrophilic. The relevant literature is reviewed.