Renal cell carcinoma metastasis in a microfollicular adenoma of the thyroid gland

A 60-year-old woman had a nephrectomy of her left kidney because of a renal cell carcinoma. She came to us for an oncologic F-18-fluordeoxyglucose-positron emission tomography (F-18-FDG-PET). In the positron emission tomography there was a pathologic fluordeoxyglucose-uptake in the left thyroid gland lobe. Thyroid investigation and Tc-99 m pertechnetate scintigraphy of the thyroid gland was done. It showed a hyperfunctioning nodule in the left thyroid gland lobe. Surgery was suggested. Histology showed a metastasis of a clear cell renal carcinoma in a microfollicular adenoma of the thyroid gland--a very rare combination.