A case report of anaplastic thyroid carcinoma transformed from small papillary carcinoma successfully detected by ultrasonography in its early stage with review of literature.

An 82-year-old woman was referred to our hospital because of a suspicious thyroid nodule. She was diagnosed with papillary microcarcinoma with a maximum diameter of 9 mm based on ultrasonography and fine-needle aspiration (FNA) cytology. She preferred observation without surgery.