Orbital Diffuse Large B-Cell Lymphoma: A Diagnostic Masquerade

Abstract Introduction: Orbital lymphomas, though uncommon, are significant masquerade syndromes that can resemble inflammatory or infectious orbital conditions like orbital cellulitis. Case Presentation: We describe the case of an 80-year-old woman who experienced sudden painful vision loss, proptosis, and limited eye movement, initially treated as orbital cellulitis with compressive optic neuropathy. The absence of clinical improvement led to further imaging and a biopsy, which identified diffuse large B-cell lymphoma. Conclusion: This case emphasizes the necessity for high clinical suspicion, particularly in older patients, and highlights the diagnostic challenges posed by steroid use and overlapping symptoms with infectious causes. We discuss the significance of a multidisciplinary approach and suggest a clinical checklist for recognizing masquerade syndromes in ophthalmology.