Carcinoid tumor occurring in a mature testicular teratoma

A rare case of a primary testicular carcinoid tumor, occurring in a mature teratoma from a 33 year old man, was examined histochemically, immunohistochemically and by electron microscopy. Both argyrophil and argentaffin reactions were positive. Immunoreactive cells for 5-hydroxytryptamine (5-HT) and gastrin were present. Electron microscopy demonstrated neurosecretory-type granules. The English literature was reviewed and this revealed at least 6 similar cases.