Background The association of subacute thyroiditis (SAT) and papillary thyroid carcinoma is a rare finding. In this study, we aimed to investigate the prevalence of differentiated thyroid cancer in a cohort of patients followed with the diagnosis of SAT. Patients and methods We retrospectively screened medical records of Endocrinology and Metabolism outpatient clinic in the past 20 years for patients with SAT. Patients with nodules and suspicious ultrasonography findings who underwent fine needle aspiration biopsy (FNAB) and operated due to malignancy risk were identified. Results We identified 137 (100 females, 37 males) patients with reliable records to confirm the diagnosis of SAT. The mean age of female patients was 41.1 ± 9.1 (range, 20-64) and of male patients was 43.0 ± 9.3 (range, 20-65). One or more FNAB was performed in 23 of the patients (16.8%) at the beginning and/or during the follow-up period when needed. Seven patients with suspicious FNAB findings were operated, and histopathological examination of the nodules confirmed the diagnosis of papillary thyroid carcinoma in 6 patients (4.4%). Conclusions Our observations suggesting a relatively higher prevalence of thyroid cancer in a small series of SAT patients warrant further studies to identify the real frequency of differentiated thyroid cancer and its association with inflammatory pathogenesis of SAT. This finding is compatible with the trend of increased thyroid cancer incidence all over the world. A repeat ultrasonography after resolution of clinical and inflammatory findings, and FNAB should be recommended to all patients with suspicious nodules.
Keywords: subacute thyroiditis; thyroid cancer; thyroid nodule; ultrasonography.