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Germ Cell Origin of Testicular Carcinoid Tumors

Authors' Affiliations: Departments of ¹ Pathology and Laboratory Medicine, and ² Urology, Indiana University School of Medicine, Indianapolis, Indiana; ³ Department of Pathology, Case Western Reserve University, Cleveland, Ohio; ⁴ Institute of Pathological Anatomy and Histopathology, School of Medicine, Polytechnic University of the Marche Region (Ancona), United Hospitals, Ancona, Italy; ⁵ Department of Pathology, Cordoba University, Cordoba, Spain; and ⁶ CellNetix Pathology, Swedish Medical Center, Seattle, Washington

Requests for reprints: Liang Cheng, Department of Pathology and Laboratory Medicine, Indiana University School of Medicine, 350 West 11th Street, Clarian Pathology Laboratory, Room 4010, Indianapolis, IN 46202. Phone: 317-491-6442; Fax: 317-491-6419; E-mail: liang_cheng{at}yahoo.com.

Purpose: Carcinoids are neuroendocrine tumors and most frequently occur within tissues derived from the embryonic gut. These tumors can occur in any organ site but are rare in the testis. The cell type giving rise to testicular carcinoid is unknown. We hypothesized that testicular carcinoid may have a germ cell origin.

Experimental Design: We describe our analysis of protein and genetic markers of germ cell neoplasia, using immunohistochemistry and fluorescence in situ hybridization, in four testicular carcinoid tumors.

Results: All four cases of testicular carcinoid tumor arose in a background of mature teratoma. Isochromosome 12p was identified in carcinoid tumor cells in all four samples. 12p overrepresentation was also observed in three cases. Isochromosome 12p and 12p overrepresentation were present in cells of coexisting mature teratoma in three cases. Carcinoid tumors showed strong immunoreactivity for synaptophysin and chromogranin, but no immunoreactivity for OCT4, CD30, c-kit, TTF-1, and CDX2. Membranous and cytoplasmic staining for β-catenin was detected in three cases.

Conclusion: Our findings suggest that testicular carcinoid represents a phenotypic expression of testicular teratoma and is of germ cell origin.