Introduction
Anaplastic thyroid cancer (ATC) is a rare cancer that is found in about 1% of thyroid malignant tumors and has an extremely poor prognosis. Generally, papillary thyroid carcinoma (PTC) grows slowly, but when it exhibits a rapid growth, it is necessary to bear in mind the anaplastic transformation. It is known that most of anaplastic transformation occurs in primary lesions, but rarely occurs in cervical lymph node lesions or distant metastasis lesions.
We have experienced cases in which metastatic cervical lymph nodes have undergone anaplastic transformation. In this manuscript, we report our experience with courses and outcomes of a patient demonstrating papillary carcinoma in primary lesion but showing anaplastic transformation in the metastatic cervical lymph nodes with rapid recurrence after surgery.