Thyroid paraganglioma: A diagnostic pitfall in thyroid FNA

Abstract

BACKGROUND: Thyroid paragangliomas are extremely rare and often are misdiagnosed by preoperative fine-needle aspiration (FNA) because their cytologic features overlap with those of other thyroid neoplasms. The objective of this study was to review the cytomorphology in a series of thyroid paragangliomas and correlate the findings with histopathology. METHODS:Five thyroid paraganglioma cases that underwent FNA were reviewed. Their clinical presentation, radiology features, cytomorphology, ancillary tests, and histopathology were analyzed. RESULTS: All patients were women with an average age of 49 years (age range, 35-61 years) and presented with an asymptomatic, solitary thyroid nodule. Radiologically, these nodules (size range, 1.8-3.0 cm) were well circumscribed, hypoechoic, and hypervascular. FNA smears showed clusters of loosely cohesive, medium-to-large epithelioid cells with clear-to-eosinophilic and occasionally foamy cytoplasm that had indistinct cytoplasmic borders. The nuclei were round to oval with focal nuclear membrane irregularities, inconspicuous nucleoli, focal marked anisonucleosis, and occasional intranuclear pseudoinclusions. Naked nuclei, variable numbers of plasmacytoid cells, multinucleated giant cells, and sustentacular cells were present in the background along with blood vessels and lymphocytes. Cytology diagnoses were incorrect and included follicular neoplasm (n = 4) and follicular lesion of undetermined significance (n = 1). Final histopathology with immunohistochemistry revealed conventional paraganglioma (n = 3) or sclerosing paraganglioma with invasive features (n = 2). CONCLUSIONS: All thyroid paragangliomas were misdiagnosed on FNA as follicular neoplasms, in part because of the rarity of these tumors in this location and cytomorphology mimicking follicles.The absence of colloid, the presence of naked nuclei, focal marked anisonucleosis, and the presence of sustentacular cells are important cytology clues.

Cytologic and histological features of rare nonepithelial and nonlymphoid tumors of the thyroid

“…[43][44][45][46] Specifically, soft tissue paragangliomas show diffuse positivity for synaptophysin (98%) and S100 (80%) and focal positivity for keratins (5%), while carotid body paragangliomas have focal positivity for S100 (2%) and negativity for keratin and synaptophysin. 44 A study by Satturwar et Cancer Cytopathology August 2021 al 47 that included 5 thyroid paragangliomas yielded positivity for synaptophysin and chromogranin, as well as S100 of sustentacular cells, but negative staining for pankeratin, TTF-1, thyroglobulin, calcitonin, CEA, and HBME. Hence, based on this limited case series, the immunohistochemical profile of thyroid paragangliomas seems to best match that of soft tissue paragangliomas and not carotid body tumors.…”

“…Loss of SDHB is observed in tumors from patients with germline SDHX mutations. 1,2,[43][44][45][46][47][48][49][50]…”

Immunocytochemistry for diagnostic cytopathology—A practical guide

“…The use of an ICC panel, ideally on CB material, is recommended. The most common scenarios are listed in Table 3 61–70 …”

Fine-needle Aspiration Washout Precipitation Specimens: An Acceptable Supplement to Genetic Mutation Detection of Thyroid Nodules

“…[ 4 , 5 ] However, the limitations of FNA include nondiagnostic modality, indeterminate cytology, and false-negative and false-positive results, which are 10.0%–40.0% of all cytological results. [ 6 , 7 ] An indeterminate cytopathology report results in difficult clinical decisions. The options for management may include sonographic monitoring, repeat FNA, or surgical removal.…”