Primary carcinoid tumor of kidney. Light and electron microscopy, and immunohistochemical study

We present a case of primary renal carcinoid tumor with the appearance of type B carcinoid with trabecular and ribbon-like structure. All the immunohistochemical stains were negative. Electron microscopy revealed numerous cytoplasmic granules with polar distribution and masses of intermediate microfilaments. We believe only 8 cases have been reported in the literature.