THYROID PARAGANGLIOMA - A CLINICOPATHOLOGICAL AND IMMUNOHISTOCHEMICALSTUDY OF 3 CASES

We report three cases of intrathyroidal paraganglioma. The patients we re adult women without significant personal or family histories that p resented with an asymptomatic thyroid nodule. The tumors were single, well-circumscribed solid masses, 2 cm in greatest diameter, located wi thin one thyroid lobe. Microscopically, they were encapsulated and sho wed the typical nesting (Zellballen) pattern of paraganglioma in other sites. Two of the tumors were composed of small-to medium-sized cells with granular amphophilic cytoplasm, and the third consisted of relat ively large cells having a similar staining quality. Immunohistochemic ally, all tumors showed positivity for neuron-specific enolase, chromo granin A, and synaptophysin. S-100 protein-positive sustentacular cell s were demonstrated in each case. Negative staining for epithelial mar kers, thyroglobulin, carcinoembryonic antigen, calcitonin, calcitonin gene-related peptide, serotonin, vimentin, and Congo red excluded othe r turners that were considered in the differential diagnosis, such as medullary carcinoma, hyalinizing trabecular adenoma, atypical follicul ar adenoma, Hurthle-cell neoplasm, and metastatic carcinoid tumor. The patients were alive and well without evidence of recurrent disease at the time of the last follow-up. The previous literature on these tumo rs is discussed. We conclude that intrathyroidal paraganglioma exists and that this tumor can be distinguished from other similar-appearing neoplasms in this organ.