FDG PET-negative liver metastases of a malignant melanoma and FDG PET-positive Hurthle cell tumor of the thyroid

A Hurthle cell tumor (oncocytoma) of the thyroid presented as a hypermetabo lic focus in a fluo-rodeoxyglucose positron emission tomography (FDG PET) s tudy which was performed as staging procedure in a patient with malignant m elanoma. This finding led to the initial diagnosis of a metastasis. In cont rast, multiple liver metastases, seen on MRI and sonography, did not show a ny increased FDG uptake, Cytology results of one liver mass confirmed a mel anoma metastasis, and of the neck mass, a Hurthle cell tumor. The Hurthle c ell tumor was, based on clinical evidence, thought to be benign. This is th e first description of a FDG PET-positive benign Hurthle cell tumor, with F DG PET-negative liver metastases of a malignant melanoma, in the same patie nt.