MON-351 A Case of Papillary Thyroid Cancer with Development of Non-Iodine-Avid, Non-Hypermetabolic Liver Metastasis

Abstract Disclosure: S. Wang: None. V. Del Signore: None. A. Hageboutros: None. F.H. Morgan: None. Background: Papillary thyroid cancer is the most common type of differentiated thyroid cancer (DTC), accounting for over 85% of all DTC cases. Metastasis is rare, and primarily localized to the lungs or bones. Metastatic lesions to the liver are noted in less than 1% of cases, and consequently few cases are reported in the literature. Furthermore, most of these reports detail liver metastases found via iodine-avidity on whole body radioactive iodine (RAI) uptake scan or hypermetabolism on positive emission tomography (PET) scan. Clinical Case: Here we describe the clinical presentation, workup, and treatment course of a 72-year-old woman with a past medical history of papillary thyroid cancer (PTC) found to have incidental pulmonary nodules measuring up to 15mm following evaluation for new onset back pain. The patient’s PTC was initially diagnosed and treated with surgical resection and 150mci of radioactive iodine more than 15 years prior to this diagnosis of recurrent disease. Until the incidental imaging finding, there was no ultrasonographic or biochemical evidence of recurrence. Subsequent thyrogen-stimulated thyroglobulin levels were significantly elevated to 452 ng/mL, raising concern for additional metastatic lesions. Whole-body RAI scan and PET scan again noted the pulmonary nodules, but no evidence of recurrent disease in the thyroid bed, lymphadenopathy, or other metastases. MRI of the abdomen noted liver lesions which were radiographically favored to be hemangiomas on both initial and second review. Repeat MRI abdomen 6 months later noted significant growth in size of the hepatic mass, from 3.8 cm to 5.4 cm, raising further concern for malignancy. Core biopsy confirmed to be metastatic thyroid carcinoma. Genomic analysis of the specimen noted a NRAS p.Q61K mutation. Patient was started on tyrosine-kinase inhibitor therapy with levantanib with noted reduction in disease burden. Conclusion: Cross sectional imaging is important in the evaluation of thyroid cancer as not all metastatic disease will be radioactive iodine avid. When thyroglobulin levels suggest distant metastasis, biopsy of even atypical sites of metastasis should be considered. Presentation: Monday, July 14, 2025