Primary carcinoid tumor of the kidney: a light and electron microscopic, and immunohistochemical study.

We report a case of primary carcinoid of the kidney. The neoplasm had a trabecular growth pattern and was argyrophil positive and argentaffin negative. An extensive battery of immunohistochemical stains was negative for specific peptide products and keratin. Electron microscopy disclosed numerous cytoplasmic membrane-bound electron-dense core secretory granules and masses of intermediate microfilaments. A review of the pertinent medical literature revealed 5 previously reported cases.