Clinically significant, isolated metastatic disease to the thyroid gland.

Despite being second only to the adrenal glands in terms of relative vascular perfusion, the thyroid gland is a rare site of metastatic disease; but when thyroid metastases occur, long-term survival has been reported to be dismal. To determine the incidence and management of isolated, metastatic disease to the thyroid, we reviewed our clinical experience. Between June 1986 and August 1994 ten patients underwent thyroidectomy for isolated, metastatic disease of nonthyroidal origin (mean +/- SD age 58 +/- 6 years, 30% female). The primary tumors were renal cell carcinomas (RCCs) (n = 5), esophageal adenocarcinoma (n = 1), pulmonary squamous cell carcinoma (n = 1), gastric leiomyosarcoma (n = 1), lingual squamous cell carcinoma (n = 1), and parotid gland carcinoma (n = 1). Three patients underwent preoperative fine-needle aspiration (FNA), all of which were suggestive of metastatic disease. The mean time from resection of the primary tumor to thyroid metastases was 3.5 +/- 6.0 years (range 0-19.5 years). Total thyroidectomy (n = 5) or lobectomy (n = 5) was performed without morbidity or mortality. After a median follow-up of 5.2 years six patients are alive and two are free of disease. Moreover, no patients have had recurrent disease in the neck. Thus carcinomas metastatic to the thyroid represent a rare cause of clinically significant thyroid disease, with RCCs comprising 50%. Most thyroid metastases (80%) present within 3 years of primary tumor resection, but with RCC they can occur as late as 19 years. The diagnosis of metastatic disease should be suspected in patients with even a remote history of cancer, especially RCC, and an FNA revealing clear cell or spindle cell carcinoma. Contrary to previous reports, long-term survival can be achieved after resection of the metastatic tumor. Furthermore, thyroidectomy may also palliate/prevent the potential morbidity of tumor recurrence in the neck.