[Thyroid metastasis from renal carcinoma. Clinical case].

Metastatic thyroid tumours are uncommon among reported clinical cases, but are more frequent in autopsy series. The most common sites of the primary tumours are the breast (21%), kidney (12%) and lung (11%) and in some cases are detected only at autopsy. The clinical presence of thyroid tumefaction, whether associated or not with compressive symptoms, in a patient with a history of surgical treatment for renal cell carcinoma should lead to the suspicion of a metastatic nodule. The most important diagnostic technique is cytological examination after fine needle aspiration biopsy, combined with immunohistochemical staining. Total thyroidectomy, whether associated or not with radiation therapy, is the procedure of choice in these cases, when possible, above all in the presence of regional symptoms. In spite of treatment, however, the prognosis of metastatic disease is very poor. Therapeutic measures allow a mean survival of 34 months in the various reported series. The authors report the case of a 66-year-old female patient who had undergone left-side nephrectomy for a renal cell carcinoma 7 years earlier. The woman presented an increased thyroid volume mainly on the right side, with signs of tracheal compression. Ultrasonography of the thyroid gland and fine needle aspiration cytology showed malignant features. Scintigraphy strongly suggested the presence of a cold nodule in the right lobe. Subsequently, total thyroidectomy was performed and the histological examination revealed that the nodule was composed of tumour cells with abundant clear cytoplasm and round nuclei; with the characteristics of the renal cell carcinoma resected 7 years previously. Since computed tomography revealed secondaries in the lungs, the patient is still being managed with chemotherapy, with arrest of the metastatic progression, and is in a fairly good clinical condition.