Rectus Muscle Metastasis from Primary Uveal Melanoma: A Case Series and Literature Review.

Introduction: We aim to describe 2 patients with metastatic uveal melanoma who developed metastases to the contralateral rectus muscles and review the literature on this rare presentation. Case Presentations: Patient 1 was a woman in her 60s with a history of cirrhosis who presented with a medium-sized choroidal melanoma in the right eye that was treated with plaque brachytherapy. She underwent regular hepatic imaging for surveillance post-treatment. Two-and-a-half years later, she developed diplopia, and a left medial rectus muscle lesion was found on MRI imaging. Biopsy was consistent with metastatic uveal melanoma. Systemic therapy with tebentafusp was initiated. The lesion slowly progressed over 2 years. The patient passed away from complications from her cirrhosis. Patient 2 was a man in his 70s with a large choroidal melanoma in the left eye treated with enucleation. He had metastatic disease at the time of diagnosis that was treated with multiple systemic therapies. Metastases to the right superior and lateral rectus muscles were noted on MRI imaging and were initially observed. He developed painful proptosis and was found to have acute enlargement of the lesions. Treatment with 30 Gy external beam radiation to the right orbit was performed with good local response. He passed away from tumor progression. Conclusion: Metastasis to rectus muscles from uveal melanoma has historically been exceedingly rare. These cases highlight new challenges in treating symptomatic intraorbital metastasis as surgical outcomes and survival improve in patients due to advances in systemic therapy.