Anaplastic transformation in lung metastases of differentiated papillary thyroid carcinoma: an autopsy case report and review of the literature.

Anaplastic transformation of papillary thyroid carcinoma is a rare condition and is associated with an aggressive behavior. Most cases described in the literature have occurred in the thyroid gland or in the surrounding cervical lymph nodes. We report a case of an 83-year-old man who, 10 years after being treated for a conventional papillary thyroid carcinoma, presented with widespread metastases in his lungs. At autopsy, he was found to have extensive metastatic deposits in both lungs, which histologically and immunohistochemically were consistent with papillary thyroid carcinoma. An unusual finding was the presence of solid pleomorphic foci within tumor deposits, consistent with anaplastic transformation.