MON-468 Hypoechoic Nodule Is Not Always the Bad Guy: Lessons Learned from a Patient with Subacute Painful Thyroiditis

Introduction: The diagnosis of subacute painful thyroiditis (SAT) is primarily based on clinical manifestations (thyroid tenderness and diffuse goiter). Suppressed TSH, elevated erythrocyte sedimentation rate (ESR) and low thyroid uptake help confirm the diagnosis. Thyroid ultrasonography and fine-needle aspiration biopsy (FNAB) are rarely necessitated. SAT produces a typical sonographic findings of ill-defined heterogeneously hypoechoic areas, which is difficult to differentiate from thyroid carcinoma. We herein report a patient with SAT who was initially diagnosed as malignancy. Case Presentation: A 36-year-old female had pain and swelling at the left thyroid gland for 3 weeks. A left thyroid nodule was diagnosed by her primary care physician. Ultrasonography revealed a poorly defined hypoechoic nodule measuring 2.5x1.1x1.5 cm at the mid pole of the left thyroid gland, for which biopsy was recommended. The nodule showed peripheral vascularity and no calcification. No suspicious cervical lymphadenopathy was detected. Histologic analysis from core biopsy found findings consistency with follicular neoplasm. Thyroid function tests were within normal range. She was treated with ibuprofen as management of thyroid pain and referred for surgery. However, the repeated ultrasonography was performed by endocrinologist in the next 2 weeks and found an interval reduction in size of hypoechoic lesion. FNAB was performed due to the risk of infiltrative malignancies. Cytologic analysis was compatible with SAT. ESR was slightly elevated. Surgery was cancelled and she was treated with ibuprofen. Two weeks later, she reported that the left thyroid pain and swelling had subsided. However, she developed thyroid pain associated with glandular tenderness and swelling of the right thyroid. On sonographic examination, the right lobe, which was previously normal was now similarly affected. Thyroid function showed thyrotoxicosis. The patient was given a further course of beta-blocker, ibuprofen and prednisolone for 2 weeks and recovered well. On follow-up at 2 months, the patient developed biochemical hypothyroidism and received levothyroxine replacement. The lesions in the thyroid gland were not visualized in the 6-month follow-up sonography. Conclusion: The ultrasonographic features of the thyroid during the acute stage of SAT may mimic thyroid carcinoma. Awareness of the sonographic findings and interval changes of SAT lesions may helpful for proper diagnosis and treatment of SAT.