Metastatic malignant melanoma to the thyroid gland detected by FDG-PET imaging

The thyroid gland is a rare site of metastasis and there have been very few reports of metastatic involvement of the thyroid from malignant melanoma. A 52-year-old female, who was initially diagnosed to have melanoma of the skin on the left breast, was thought to be disease-free following excision until she underwent FDG-PET for a whole body survey 16 months later. FDG-PET showed foci of uptake in the left thyroid lobe, right costophrenic angle, the right hepatic lobe anteroinferiorly, and the left chest wall. The latter corresponded to a palpable nodule at that site. A chest CT chest demonstrated a lung nodule corresponding to the site of uptake at the right costophrenic angle. An ultrasound examination of the neck revealed several thyroid nodules which were identified in both lobes. The largest nodule was in the mid portion of the left lobe and this had a densely calcified rim. Histopathologic examination was most consistent with a metastatic lesion from malignant melanoma. © 2007 Lippincott Williams & Wilkins, Inc.