(A, B) Papillary thyroid carcinoma at 23 years of age. (C, D) Recurrent papillary thyroid carcinoma after 5 years. Poorly differentiated cells are seen at focal areas of the papillary thyroid carcinoma. (E, F) Recurrent anaplastic thyroid carcinoma in the pretrachea adjacent thyroid bed.Anaplastic Transformation of Papillary Thyroid Carcinoma in a Young Man: A Case Study with Immunohistochemical and BRAF Analysis. Park JH, Kwon HJ, Park CS, Hong S - Korean journal of pathology (2014) Not Altered. CC.