Testicular Carcinoid : Differential
Primary well-differentiated neuroendocrine tumor (carcinoid) of the testis must be distinguished from metastasis to the testis. Features favoring metastasis include: bilateral involvement, multifocality, vascular invasion, extratesticular extension, and clinical history of a primary elsewhere. The lack of these features and the presence of other teratomatous elements points to primary WDNET of the testis.
This image of a primary testicular carcinoid shows small and medium sized nests of uniform tumor cells in a fibrotic stroma.