Recurrent Thyroid Cancer with Changing Histologic Features

We present the case of a 57-year-old woman diagnosed with breast cancer and a thyroid mass that was suspicious for cancer. The breast cancer was estrogen and progesterone receptor negative, HER2/neu borderline, with a high proliferative index. Treatment of this cancer took precedence. Nine months later, a total thyroidectomy was done for papillary thyroid cancer with metastases to 2 of 8 perithyroid lymph nodes. Postoperative radioactive iodine ablation was given. Recurrent thyroid disease was found in the right neck 1 year later and was resected; no radioactive iodine was given at that time. After 2½ years, the cancer recurred as a more highly aggressive, undifferentiated anaplastic thyroid carcinoma. Treatment is discussed.