A man in his 20s presented to his local ear, nose, and throat (ENT) clinic with a 1-year history of progressive, unilateral left-sided nasal blockage associated with facial pain and pressure sensation over the left cheek. He also had a history of intermittent left-sided epistaxis during childhood. He was otherwise fit and healthy and not taking any regular medications.Clinical examination showed a large unilateral nasal mass filling the left nasal cavity and deviation of the septum to the right. Findings from the remainder of the ENT examination were normal.In light of the unilateral nature of the clinical signs and symptoms, the patient underwent imaging with computed tomographic (CT) imaging ( Figure 1A) and magnetic resonance imaging (MRI) of the paranasal sinuses ( Figure 1B and C). Both scans confirmed the presence of a soft-tissue heterogenous mass within the left antrum, with clinically significant widening of the maxillary sinus ostium permitting extension of the antral mass into the left nasal cavity. There was also associated expansion and signs of pressure erosion of the medial and superior walls of the antrum with bony dehiscence of the left orbital floor. The mass extended posteriorly into the nasopharynx and displaced the nasal septum to the right.The patient was subsequently admitted for examination under anesthesia and biopsy of the left nasal mass. Postoperatively, he developed clinically significant epistaxis from the left operated side, requiring nasal packing. Following histological diagnosis, he was referred to our center for definitive treatment.