Anaplastic Transformation in Mandibular Metastases of Follicular Variant of Papillary Thyroid Carcinoma: A Case Report and Review of the Literature.

Anaplastic transformation of well-differentiated thyroid carcinomas at distant metastatic sites is a rare condition. Most cases described in the literature have occurred in the thyroid or regional lymph nodes. We report a case of anaplastic transformation of the follicular variant of papillary thyroid carcinoma in mandibular metastases. A 76-year-old female presented with a painful and enlarging mandibular mass. She had been treated in the past for the follicular variant of papillary thyroid carcinoma. A palliative hemi-mandibulectomy was performed. Histology revealed a metastatic papillary thyroid carcinoma, follicular variant, with an unusual finding of solid pleomorphic epithelioid and spindle cell areas, consistent with anaplastic transformation.