Germ cell origin of testicular carcinoid tumors.
OBJECTIVE
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.


METHODS
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 beta-catenin was detected in three cases.


CONCLUSIONS
Our findings suggest that testicular carcinoid represents a phenotypic expression of testicular teratoma and is of germ cell origin.
Abbosh
Phillip H
PH
Department of Pathology and Laboratory Medicine, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA.
Zhang
Shaobo
S
Maclennan
Gregory T
GT
Montironi
Rodolfo
R
Lopez-Beltran
Antonio
A
Rank
Joseph P
JP
Baldridge
Lee Ann
LA
Cheng
Liang
L
D000328:Adult; D014408:Biomarkers, Tumor / Q000378:metabolism*; D002276:Carcinoid Tumor / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D002864:Chromogranins / Q000378:metabolism; D002881:Chromosomes, Human, Pair 12 / Q000235:genetics; D006801:Humans; D007124:Immunoenzyme Techniques; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D016708:Synaptophysin / Q000378:metabolism; D013736:Testicular Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D051176:beta Catenin / Q000378:metabolism
D014408:Biomarkers, Tumor; D002864:Chromogranins; D016708:Synaptophysin; D051176:beta Catenin