Primary Epithelial Neuroendocrine Tumors of the Retroperitoneum.

Neuroendocrine tumors are either epithelial or neural in origin. Neuroendocrine tumors of the retroperitoneum are mostly metastatic. Primary epithelial neuroendocrine tumors of the retroperitoneum are exceedingly rare. We describe a case of a retroperitoneal tumor that was discovered incidentally during exploratory laparotomy for small-bowel obstruction. Histopathologic and immunochemical analyses of the biopsied mass were consistent with an epithelial neuroendocrine tumor. The tumor was subsequently removed and final analyses confirmed the initial diagnosis. No evidence of lymph nodes or paraganglia were found within the tumor on histologic examination. Extensive evaluation did not reveal any other primary or metastatic lesions. Therefore, the diagnosis of primary epithelial neuroendocrine tumor of the retroperitoneum was made. The literature is reviewed and discussed. To date, this is only the fifth reported case of primary epithelial retroperitoneal neuroendocrine tumor. Although extremely rare, the possibility of such diagnosis should be included in the differential diagnosis of a retroperitoneal tumor.