A very unusual thyroid tumor: a nodule with mature fat papillary hyperplasia and focal atypia.

Fat-containing lesions of the thyroid are rare, encompassing several clinical-pathological conditions such adenolipomas, thyrolipomatosis and lipomotous tissue in case of amyloidosis. Furthermore, cases of papillary thyroid carcinoma have been identified in association with thyrolipomatosis. We report a case of 51 years old man referred to surgery for a multinodular goiter, showing multiple cystic and hemorrhagic nodules of up to 3 cm. One of these lesions showed features of papillary hyperplasia with focal cytological atypia and mature fat. Here, we describe and discuss the histological and immunophenotypical features of this rare lesion.