Objective: Thyroid paragangliomas are rare tumors, and both preoperative and postoperative differential diagnosis is difficult. We report the case of a 24-year-old man with a thyroid paraganglioma and the ultrasonographic imaging, histologic, and immunohistochemical findings.
Design: The patient presented with an asymptomatic thyroid nodule. An ultrasonogram showed a 3-cm-diameter solid nodule in the upper portion of the right lobe of thyroid, and color Doppler ultrasonography revealed intranodular hypervascular flows. Fine-needle aspiration biopsy yielded single cells and loose clusters of round to oval cells containing ovoid nuclei. A clinical diagnosis of follicular thyroid tumor was made, and right thyroid lobectomy was performed. The tumor was encapsulated and exhibited a prominent lobular pattern. To differentiate between thyroid paraganglioma and other thyroid neoplasms, paraffin sections of the specimen were immunochemically stained with antibodies to calcitonin (CT), carcinoembryonic antigen (CEA), chromogranin A, neuron-specific enolase (NSE), S-100, and thyroglobulin.
Main outcome: The immunohistochemical staining was positive for chromogranin A and NSE and negative for thyroglobulin, CT, CEA, and S-100. Congo red staining was also negative. Based on these findings, final diagnosis of thyroid paraganglioma was made.
Conclusions: The definitive diagnosis of paraganglioma is made on the basis of the results of immunohistochemical staining. The diagnosis of thyroid paraganglioma is difficult to make both preoperatively and postoperatively.