Choroidal metastasis as initial presentation of aggressive medullary thyroid carcinoma with widespread mediastinal, brain, pituitary, bone, lung, and liver metastasis: Case report and literature review

Introduction: Medullary thyroid carcinoma (MTC) is a neuroendocrine tumor that originates from the parafollicular C cells of the thyroid gland. MTC can be due to sporadic or hereditary causes due to gain of function germ line mutations in the RET proto-oncogene. MTC presenting as ocular symptoms due to choroidal mass is rare with bad prognosis. Presentation of case: A 38-year-old Sudanese male presented to Hamad General Hospital, complaining of sudden painless decrease of vision of the right eye of 3 weeks duration. After investigations using imaging methods, the patient was discovered to have metastatic MTC that presented as choroidal mass and metastasized to his lung, bone, brain, pituitary, liver and mediastinum. Discussion: In terms of investigations, serum levels of calcitonin have superior diagnostic accuracy. Our patient undertook diagnostic imaging including ultrasonography, fine needle aspiration and computerized tomography (CT) scan and/or MRI imaging. He undertook total thyroidectomy and left neck dissection followed by stereotactic radiosurgery for the right orbit and pituitary. He then received systemic anti-RET therapy (Selpercatinib). At 5 months follow up there was dramatic drop in CEA from 888 μg/L to 164 μg/L, and calcitonin from >585.2 pmol/L to 354 pmol/L. Conclusion: Choroidal metastasis as initial presentation of MTC is extremely rare and challenging to diagnose. Surgeons need a high index of suspicion when ocular symptoms accompany a neck mass or thyroid-related symptoms. MTC has a progressive course with involvement of blood vessels and neck lymph nodes. Choroidal metastasis of MTC is challenging to manage.