Primary renal carcinoid.

A case of primary renal carcinoid in a 34-year-old man is reported. The lesion was morphologically identical to carcinoid tumors arising in the gastrointestinal or respiratory tracts. The renal carcinoid was focally argyrophilic and contained chromogranin and neuron-specific enolase disclosed by immunohistochemical studies. The diagnosis was further confirmed by membrane-bound cytoplasmic neurosecretory granules visualized by electron microscopy. The possible histogenesis of this unusual tumor and a review of the literature are discussed.