THU673 Unusual Metastasis Of Differentiated Thyroid Carcinoma

Disclosure: M. Aiad: None. O.A. Aluko: None. B. Bhatt: None. Background: Papillary thyroid cancer (PTC) is the most common form of differentiated thyroid malignancy. Distant metastasis of PTC are rare and usually occur in the bones, lungs, and lymph nodes of the neck. Retinal and skin metastases are extremely rare. We present a case of PTC with metastasis to the distal extremity with sites including retina, skin and breasts. Clinical Case: A 40-year-old Caucasian female with a past medical history of papillary thyroid cancer at age 16 status post total thyroidectomy followed by two radioactive iodine treatments, who is incidentally found to have recurrent metastatic disease to lungs, retina, subcutaneous soft tissue and bones. After having an accident, trauma CT revealed pulmonary nodules and around the time patient started to notice subcutaneous lumps on the chest and gradually worsening blurry vision indicating further imaging as well as ophthalmological evaluation. The biopsy of the right lower lung nodules showed metastatic differentiated follicular variant papillary thyroid cancer, positive for RET mutation. TSH was appropriately suppressed at 0.128uIU/mL on levothyroxine 100 mcg daily, with elevated thyroglobulin level 47ng/mL and antibody 1.7IU/mL. The molecular testing was positive for RET gene mutation; thus she started targeted therapy with selpercatinib 120 mg twice daily. Shortly after starting therapy, she presented to the ER with complaints of headaches and refractory nausea. Imaging done showed evidence of intracranial metastases, bilateral intraocular lesions in the posterior globe as well as intraventricular hemorrhage. She received IV steroids, selpercatinib was held due to the possibility of exacerbating intraventricular hemorrhage. Following multidisciplinary discussion between neuro-oncology and radiation oncology, she started stereotactic radiotherapy (SRT) to choroidal plexus lesions with a plan to restart systemic therapy once SRT is completed. Conclusion: The epidemiological aspects of thyroid metastases in rare sites are likely unknown and could significantly impact patient management. Most cases of uncommon metastasis have been reported after several years of diagnosis such as in our patient who developed multiple metastasis to rare sites including skin, retina, breast and choroid plexus. Presentation: Thursday, June 15, 2023