Non-Epstein-Barr Virus Sinonasal Undifferentiated Carcinoma Presenting as Diplopia and Rhinorrhea

Sinonasal undifferentiated carcinoma (SNUC) is an extremely rare and highly aggressive malignant neoplasm of the nasal cavity and/or paranasal sinuses. SNUC is clinicopathologically distinctive from other tumors but is difficult to study due to its low incidence. There is also very little consensus about the etiology of SNUC, including its association with Epstein-Barr virus (EBV). Treatment modalities include surgery, chemotherapy, and radiation depending on the stage and grading. Herein, we discuss a patient who presented to the emergency department with chronic rhinorrhea and various ophthalmologic symptoms such as flashes, floaters, and diplopia. The patient was later diagnosed with SNUC in the setting of negative serological testing for EBV in addition to his previously concomitant history of bladder cancer. The purpose of this case report is to contribute to the broader literature of SNUC and the specifics surrounding the diagnostic modalities utilized, management, and outcome of non-EBV sinonasal undifferentiated carcinoma in a patient with atypical symptomatology.