Subacute granulomatous thyroiditis mimicking thyroid carcinoma: diagnostic challenges

Abstract

Background: Subacute granulomatous thyroiditis (SGT) is a self-limiting inflammatory disease of the thyroid gland, often associated with viral infections. It is typically diagnosed through clinical and laboratory evaluation, although ultrasonography can be a useful adjunct. However, the most common ultrasonographic finding—nodular hypoechoic areas—may raise suspicion for other pathologies, such as thyroid carcinoma. Case Description: A 34-year-old female patient presented with neck pain and progressive odynophagia. Thyroid ultrasound and cytology revealed a suspicious thyroid nodule. Ultrasonography showed a nodule in the right lobe measuring 1,4cm x 1,8cm x 0,6cm,  with increased Doppler vascularity, and fine-needle aspiration cytology was classified as Bethesda V, suggestive of neoplasia. A right lobectomy was performed, and histopathological examination confirmed the diagnosis of SGT. Discussion: Although SGT is a benign condition, its clinical and cytological features may mimic those of thyroid carcinoma, posing a diagnostic challenge that may require more invasive procedures for histopathological evaluation and clinical decision-making. Histopathological findings such as the presence of giant cells, follicular atypia, and inflammatory patterns can lead to suspicion of malignancy. Recognizing this entity in histopathological analysis is essential. Conclusion: It is important to correlate clinical, laboratory, and imaging findings in the evaluation of thyroid nodules, especially in the presence of cytological features suggestive of malignancy. In this context, considering SGT as part of the differential diagnosis is crucial to guide appropriate therapeutic decisions.