[Isolated thyroid and skin metastases of renal carcinoma]

Metastases to the thyroid gland from renal carcinoma are observed in 10% of the uncommon metastatic thyroid tumours. They are the first sign of renal carcinoma in 25% of cases or appear after primary treatment of renal neoplasia, up to 27 years later. Metastases are more frequent in pathological glands, perhaps because intraparenchymal blood flow is slowed and tissue oxygen partial pressure is reduced. Thyroid metastases are frequently associated with lung ones, whether those associated with metastases to other organs (duodenum, pancreas, skin) are very unusual. Clinical manifestations are thyroid node without hormonal modifications or acute swelling of the gland with hormonal hyperfunction; other signs are dysphonia and/or dysphagia. Thyroid nodes are "cold" at 131I scanning and with mixed structure at ultrasonography. Fine needle aspiration is often diagnostic. Problems in differential diagnosis are among clear-cell renal carcinoma and some types of thyroid adenoma, adrenal carcinoma, parathyroid carcinoma, testicular seminoma and hypernephroid thyroid carcinoma. Treatment is surgical: subtotal or total lobectomy, with or without isthmectomy, if metastasis is single, total thyroidectomy in diffuse disease. Some Authors always choice total thyroidectomy to erase microscopic foci of disease in contralateral lobe. Reported survival after treatment is from a few months to 27 years. Survival is longer with a metastasis appearing after nephrectomy and with unique versus multiple ones.