[Thyroid metastases from cancer of the kidney. Two cases]

Non-thyroid cancers rarely metastases to the thyroid gland. Metastases can be divided into those with clinical expression and those identified at necropsy. Symptom producing thyroid metastases are usually due to a primary renal cell cancer. We report two cases of thyroid metastasis of a clear cell renal carcinoma. In the first case, an 82-year-old woman presented with an enlarged thyroid gland. This inaugural element led to the diagnosis of thyroid metastasis and identification of recurrent renal cell carcinoma which had been treated by radiotherapy 24 years earlier. After radiotherapy for a concomitant pulmonary metastasis, the patient is in good general health with no signs of recurrence. In the second case, increased thyroid volume led to signs of compression in a 71-year-old man. The pathology report after left lobular thyroidectomy suggested trabecular adenoma or metastasis of a clear-cell primary tumour. Abdominal CT-scan revealed a 3.5 cm tumour found to be a clear-cell renal carcinoma at nephrectomy. Another osteolytic metastasis to the femur was also observed three months after surgery. The patient is in good health 15 months after the initial diagnosis. The significance of thyroid metastasis of renal cell carcinoma would vary according to the different cases reported in the literature with survival ranging from 32 months to 3-7 years after surgical exeresis. Prognosis would thus not appear to be as poor as for thyroid metastasis from other primary tumours.