Subacute thyroiditis (SAT) association with thyroid carcinoma has been rarely reported in the literature. We present a patient with SAT and papillary thyroid cancer that was suspected by ultrasonographic evaluation (US) following SAT treatment. A fifty-four-year old female patient referred to our department due to tachycardia, jitteriness and pain in cervical region for the past one month. SAT diagnosis was established by physical examination, laboratory and ultrasonographic findings. After treatment, control thyroid US revealed regression of the hypoechogenic regions seen in both lobes, and a previously unreported hypoechogenic lesion with microcalcification focus that had irregular borders and was not clearly separated from the surrounding parenchyma located in the posterior aspect of the lobe (Elasto score: 4, Strain index: 7.08). Fine needle aspiration biopsy was taken from this nodule; cytology was assessed to be compatible with papillary thyroid carcinoma. Postsurgical pathology evaluation showed a papillary microcarcinoma. SAT may produce ultrasound changes that obscure the coexistence of papillary carcinoma. We recommend that patients with SAT have ultrasonography after they recover. Hypoechogenic regions bigger than 1 cm that are present in the follow-up post-therapy US should be assessed by biopsy.
