K. L. Long1, S. Spires2, C. Lee1, D. Sloan1 1University Of Kentucky,Division Of General Surgery,Lexington, KY, USA 2University Of Kentucky,Division Of Pathology,Lexington, KY, USA
Introduction: Metastatic disease to the thyroid gland is an uncommon clinical occurrence, accounting for 1.4-3% of patients undergoing thyroid surgery. Commonly reported cancers found in the thyroid gland include renal cell carcinoma, lung cancer, and breast cancer. Questions remain as to whether thyroid metastases from non-thyroid malignancies (NTM) have a predilection for abnormal thyroid glands. We hypothesized that patients with metastatic disease to the thyroid gland are more likely to have underlying thyroid pathology, including thyroid cancer.
Methods: A 5-year retrospective case review was performed using an IRB-approved protocol (13-0532-P6H) for patients undergoing thyroid surgery at our institution from July 2008 through June 2013. During this time, 1708 thyroid procedures were performed.
Results: Six patients with NTM were identified, 4 of which were diagnosed with renal cell carcinoma metastatic to the thyroid (66%). One patient was found to have metastatic small cell lung cancer, and one patient was diagnosed with metastatic breast cancer. The average age at presentation was 65.1 years. 4 of 6 patients were female. Additionally, 4 of the 6 patients had a history of metastatic disease to organs other than the thyroid gland. The average time from initial cancer diagnosis to the first diagnosis of metastatic disease was 8.8 years (range 0 to 26 years). The average time from initial diagnosis to evidence of thyroid involvement was 11.5 years (0 to 27 years). In final pathologic specimens, 2 of 6 patients had incidental findings of papillary thyroid cancer. 2 additional patients were noted to have abnormal thyroid pathology.
Conclusion: Non-thyroid malignancy metastatic to the thyroid remains a rare but distinct entity. Any patient presenting with a thyroid mass and even a remote history of cancer should be evaluated for metastatic disease to the thyroid gland. Metastatic disease to the thyroid gland can present at any time after a primary cancer diagnosis and includes a wide range of tumor types. Likewise, the incidence of associated thyroid pathology remains high in these patients, and operative planning should account for these factors.