Abstract
A diffuse sclerosing variant of papillary thyroid carcinoma is uncommon and has a tendency for rapid growth and a higher incidence of cervical lymph node metastases. We experienced a case of a diffuse sclerosing variant of papillary thyroid carcinoma in a 48-year-old man. This case showed benign features on initial ultrasonography and positron emission tomography (PET) scan. A new nodule was detected on follow-up ultrasonography that showed rapid enlargement. This case was confirmed by surgical excision. We herein describe the initial and follow-up ultrasonographic findings of a diffuse sclerosing variant of papillary thyroid carcinoma.