Orbital Proptosis as the Sentinel Sign of Metastatic Desmoplastic Small Round Cell Tumor: A Rare Ophthalmic Gateway to Systemic Malignancy.

Desmoplastic small round cell tumor (DSRCT) is a rare, extremely aggressive soft-tissue sarcoma that primarily develops in the abdomen of children and young adults. Orbital involvement is uncommon and typically occurs late in the disease course. We present a case of a 56-year-old male who attended the ophthalmology outpatient department with rapidly progressive, painless left-eye proptosis for 15 days. Ophthalmic examination showed axial proptosis with peripapillary flame-shaped hemorrhages; therefore, neuro-orbital imaging was performed. Magnetic resonance imaging revealed a lobulated extraconal mass with contiguous extension into the anterior temporal fossa without associated bony erosion. Systemic evaluation revealed a retroperitoneal mass and multiple hepatic lesions. Computed tomography-guided biopsy confirmed DSRCT based on typical histology and immunohistochemical positivity for Wilms tumor 1, desmin, epithelial membrane antigen, vimentin, and integrase interactor-1. The orbital mass was excised through lateral orbitotomy, and the patient received systemic therapy with imatinib and multidisciplinary oncologic care. This case is notable because orbital proptosis was the first clinical manifestation of occult metastatic DSRCT. The unusual radiological finding of extra-axial intracranial extension without bone involvement further distinguishes this presentation. Ophthalmologists should consider systemic malignancy in patients with unexplained progressive proptosis.