[A case of primary renal carcinoid tumor].

The patient was a 44-year-old woman in whom a mass of the right kidney was found when she underwent abdominal ultrasonography in a physical checkup. The computed tomography of abdomen and the magnetic resonance imaging of abdomen revealed a 3 x 3 cm solid mass at the right kidney. Excretory urograms showed a deformity of the right collecting system due to a mass lesion. The specimen of the resected tumor showed a cellular arrangement specific to carcinoid tumor and positive reaction of Grimelius stain. Electron microscopy confirmed the presence of dense-core granules in the tumor cells. Gastrointestinal investigation after the operation revealed no particular findings suggesting a carcinoid syndrome. No evidence of metastasis or recurrence was noted for 5 months after the operation. This was a very rare case of primary renal carcinoid tumor, representing the 12th case in the literature in Japan.