Metastasis to the Thyroid Gland: Report of a Large Series from the Mayo Clinic

Objectives: Metastases to the thyroid gland are not as unusual as previously believed. This study reports the largest number of patients with metastatic disease of the thyroid to date, confirms the accuracy of fine-needle aspiration (FNA) in diagnosing metastasis, and reviews the incidence and management through our institutional experience. Methods: This study entailed review of all thyroid FNAs performed at Mayo Clinic, Rochester during the period 1980 to 2010 and identified 97 patients with a metastatic solid neoplasm of the thyroid gland. Results: Frequent primary tumor sites included kidney (22%), lung (22%), and head and neck (12%). The median age at discovery of thyroid metastasis was 63 years. The time from diagnosis of primary tumor to metastasis to the thyroid gland was most considerable for renal cell carcinoma (mean 113 mo). Forty-one patients underwent thyroid resection with an average tumor size of 3 cm. Median survival in all patients with metastases was 20 months (range, 1 to 228 mo). Patients who underwent thyroid resection had a median survival of 30 months (range, 3 to 171 mo), whereas survival in patients without thyroid surgery was 12 months (range, 1 to 228 mo, log-rank test P=0.09). Conclusions: Our experience over the last 30 years confirms that FNA remains a sensitive and specific method to detect metastases to the thyroid. In any patient with a history of a malignancy, a new thyroid mass should be promptly evaluated for recurrent malignancy as early diagnosis and surgical resection resulted in a nonstatistically significant increased median survival.