8161 A Rare Case of Malignant Melanoma Metastatic to the Thyroid Gland

Abstract Disclosure: J. Ferri-Guerra: None. O. Abdulhussein: None. E. Kasper-Guerra: None. G. Madrigal Loria: None. L. El Hage: None. 69 yo female presented with neck swelling in 2014. TSH was normal. Thyroid ultrasound showed multiple nodules with a right 2.9 x 2.3 x 2.1 cm that was cold on subsequent thyroid uptake scan. FNA of the right nodule in 08/2014 showed malignant cells with spindle cell pattern thought to be medullary thyroid cancer. She was scheduled for total thyroidectomy but presented with small bowl obstruction prior to her surgery and was diagnosed with metastatic melanoma (BRAF +). Initial PET scan showed a 4.1 x 2.8 x 2.8 cm hypermetabolic right thyroid lobe lesion in addition to other multiple hypermetabolic lesions consistent with known melanoma. The thyroid FNA specimen correlated with the small bowel excision specimen and showed similar features diagnosing metastatic melanoma to the thyroid gland.She was started on ipilimumab with subsequent scan in 04/2015 showing increase in right thyroid mass size to 5.4 x 4.2 x 9 cm with mixed results of other metastatic locations. She was switched to pembrolizumab and later dobrafenib/trametinib in 05/2015. Imaging thereafter showing significant improvement including a decrease in the right thyroid nodule size to 1.6 cm x 2.5 cm x 2.4 cm with no hypermetabolic activity on further PET scans. Repeat thyroid ultrasound in 2021 showed multiple nodules with a 2.2 x 1.5 x 1 cm nodule in the right. Repeat FNA of the right nodule was benign. Last imaging in 2023 showed stable nodules. Conclusion: metastasis to thyroid gland from malignant melanoma is a rare finding and should be considered in rapidly growing thyroid nodules. These lesions can be treated with targeted therapy that can spare affected individuals surgery. Presentation: 6/1/2024