A histochemical, immunohistochemical and electron microscopic study was made on a case of ovarian strumal carcinoid arising from a mature cystic teratoma. This tumor formed a solid nodule and was histologically composed of both thyroid tissue and carcinoid tumor. In this nodule, the carcinoid component was predominant and a trabecular pattern was observed with ribbons of identical cells. Carcinoid cells had argyrophilic granules with Grimelius stain, but argyrophilic granules could not be detected in the thyroid tissue. Both components were negative to Masson-Fontana reaction. By immunoperoxidase technique, immunoreactive thyroglobulin was demonstrated within the thyroid follicles and their epithelial cells. Serotonin was positive in some of the carcinoid cells, but negative in the thyroid components. Carcinoembryonic antigen (CEA), calcitonin, cdetoprotein and adrenocorticotropic hormone (ACTH) were all negative in these components. Microfollicles or acinar structures in the intermediate zone from the thyroid tissue to the carcinoid component showed a mixed characteristic, being positive for thyroglobulin and Grimelius stain. Electron microscopically, round and densecored neurosecretory granules could be seen in the cytoplasm of the trabecular part. These findings suggest that strumal carcinoid developed in close association with the teratomatous thyroid tissue in the mature cystic teratoma of the ovary.
