Primary renal carcinoid tumor in horseshoe kidney: a case report

Primary carcinoid tumor of the kidney is a very rare entity (< 1%). About 90 cases have been reported in the literature. Carcinoid tumors appear over-represented in horseshoe kidneys compared with normal renal anatomy. Herein, we reported a 33-year-old male with primary renal carcinoid tumor arising from a horseshoe kidney. The tumor showed nests and trabeculea of uniformly polygonal cells separated by vascular stroma. The cells have fine uniform nuclei and scanty to moderate amount of eosinophilic cytoplasm. No mitosis was seen. The tumor cells were positive for cytokeratin and neuroendocrine cell marker, synaptophysin, but negative for chromogranin A. To the best of our knowledge, this is the first case of primary renal carcinoid tumor arising from a horseshoe kidney in Egypt and the 19th in the literature.