8078 TERT Positive Thyroid Nodule in the Setting of Metastatic Melanoma

Abstract Disclosure: E. Langnas: None. S. Chao: None. K.M. Gomes: None. A. Bhan: None. Metastatic disease to the thyroid gland is uncommon with a reported incidence of up to 4% in post-surgical specimens. Lung cancer is the most common primary tumor site in autopsy series. Clinically, renal cell carcinoma is the most common primary tumor site. Metastatic melanoma to the thyroid gland is clinically rare, however, in autopsy series, it has been reported with incidence of up to 39%. A 61-year-old man presented to the endocrinology clinic for an incidentally detected thyroid nodule. He had recently presented with a chronic cough, prompting a chest x-ray that revealed pulmonary nodules. Subsequent computed tomography (CT) showed numerous bilateral lung nodules measuring up to 2.5 cm and an incidental thyroid nodule. Ultrasound of the thyroid identified a 2.7 cm mixed cystic-solid right thyroid nodule. No risk factors for thyroid cancer were identified. His TSH was 3.51uIU (0.45 - 5.33 uIU/mL). The thyroid nodule was biopsied, and pathology revealed atypical spindle cells with irregular nuclear membranes and scattered histiocytes. A further review with cytopathology suggested non-thyroidal origin of the cells. Molecular testing with AFIRMA reported a telomerase reverse transcriptase (TERT) promoter mutation at C228T. The sequencing was negative for TERT C250T, BRAF, RET, PETC1, PTC3 and MTC. Due to concerns about metastatic disease, a positron-emission tomography (PET)-CT was conducted, revealing hypermetabolic lesions in numerous bilateral lung nodules, right thyroid nodule, porta hepatis lymph node, and a soft tissue nodule within the greater curvature of the gastric body. Subsequent biopsies of the right lung and gastric body confirmed the diagnosis of metastatic melanoma. On further questioning, it was found that the patient had a history of a skin lesion on his back that was excised several years ago with pathology reporting tumoral melanosis. Malignant melanoma has a poor prognosis due to high recurrence and metastatic rates. In melanoma, TERT promoter mutations are the most common mutations in noncoding regulatory regions. TERT C228T mutations and C250T mutations are seen in malignant melanoma and studies have shown that TERT promoter mutations are associated with aggressive clinical behavior. These TERT promoter mutations can also be seen in various other cancers including primary thyroid cancers with a similar association with more aggressive thyroid tumor characteristics. Our case describes a patient with a thyroid nodule and molecular testing noting a TERT promoter mutation. Both primary thyroid cancer and metastatic disease to the thyroid should be considered in these cases. This case also highlights the importance of obtaining a thorough history of prior malignancy in patients with thyroid nodules to assess the risk of metastatic disease. Presentation: 6/1/2024