Subacute thyroiditis presenting as a painful suspicious thyroid nodule

SUMMARY: We report a case of subacute thyroiditis in a 40-year-old female who initially presented with painful thyroid nodules without clinical and biochemical evidence of hyperthyroidism. Thyroid ultrasound was done to evaluate the thyroid nodules and fine-needle aspiration (FNA) was performed in view of the suspicious features. As the FNA showed a follicular lesion of undetermined significance or atypia of undetermined significance (FLUS/AUS, Bethesda III), she was advised for surgical excision. She was subsequently diagnosed with subacute thyroiditis based on her clinical symptoms, biochemical evidence of hyperthyroidism, raised erythrocyte sedimentation rate (ESR) as well as low uptake on thyroid scintigraphy. The thyroid lesions disappeared after symptomatic treatment. It is important to recognise that subacute thyroiditis can present with painful thyroid lesions with ultrasound features similar to suspicious thyroid nodules which can resolve with the resolution of the thyroiditis. LEARNING POINTS: Subacute thyroiditis can present with atypical features such as the absence of pain, normal erythrocyte sedimentation rate or absence of hyperthyroidism. In subacute thyroiditis, ultrasound findings are commonly described as focal or multifocal lesions with poorly defined and heterogeneous and hypoechoic echogenicity which can be misdiagnosed as malignancy. Thyroid lesions can resolve with the resolution of thyroiditis with or without symptomatic treatment.