Intrathyroid metastases (ITM) in literature are considered rare and with a dismal prognosis. The aim of this study is to detect which neoplasms metastasize most often to the thyroid gland, their clinical features, and treatment options.

Retrospective analysis of clinical files of patients submitted to surgery for thyroid disease over 16 years at 5 tertiary referral centers. 18 patients (median age 67,7 years) were affected by ITM.

The site of the primary tumor was: kidney (15), lung (2), melanoma (1). The mean delay from the primary tumor was 127+/-18 months. Seven patients (40%) complained of preoperative symptoms, in the others, thyroid involvement was incidentally discovered during the follow-up for the primary cancer. 12 patients (67%) underwent total thyroidectomy, 6 thyroid lobectomy. Morbidity was 28% (3 recurrent nerve palsies with 2 nerves involved by tumor, and 2 transient hypoparathyroidism) mortality was nil. The median follow-up was 23 months and 5 year overall survival after thyroid surgery was 90%.

Even if thyroid metastases are rare, we recommend thyroid imaging be included in the follow-up of tumors known to be prone to metastasize to the thyroid. Fine-needle agobiopsy (FNAB) with immunohistochemical stains may help in preoperative workup. A long delay between the primary tumor and the recurrence warrants surgery since long survival can be achieved. Due to the high complication rate, these patients should be referred to high-volume centers