Thyroid Paraganglioma Diagnosed by Fine-Needle Aspiration Biopsy, Correlated With Histopathological Findings: Report of a Case.

Thyroid paragangliomas are rare neuroendocrine tumors. They are difficult to diagnosis by fine-needle aspiration biopsy (FNAB) and can be misdiagnosed as other types of thyroid disease. Here, we present an unusual case of primary thyroid paraganglioma diagnosed by FNAB. A 66-year-old woman presented with multinodular goiter. Ultrasound (US)-guided FNAB of the 3 cm nodule in the superior portion of the right lobe of the thyroid was performed. The cytological smears showed single cells or loose clusters of round to ovoid cells with oval granular nuclei. To differentiate between thyroid paraganglioma and other thyroid neoplasms, cell block material from the FNAB specimen was immunohistochemically stained with antibodies to thyroglobulin, calcitonin (CT), AE1-AE3, carcinoembryonic antigen (CEA), synaptophysin, chromogranin A (CH-A), neuron-specific enolase (NSE), thyroid transcription factor-1 (TTF-1), parathyroid hormone (PTH), and S-100. Immunohistochemical staining was positive for synaptophysin, CH-A, NSE, and S-100, and negative for thyroglobulin, CT, AE1-AE3, PTH, CEA, and TTF-1. Congo red staining was also negative. Paraganglioma and other neuroendocrine neoplasms were considered in the differential diagnosis. A total thyroidectomy was performed, and a final diagnosis of paraganglioma was made. Paraganglioma is a rare neuroendocrine tumor of the thyroid and should be considered in the differential diagnosis based on cytology of thyroid neuroendocrine tumors. Immunohistochemistry should be performed when making a diagnosis of thyroid paraganglioma, particularly when evaluating fine-needle aspiration smears. Diagn. Cytopathol. 2016;44:643-647. © 2016 Wiley Periodicals, Inc.