RESUMEN
A 68-year-old Chinese man presented with an eight-month history of pyrexia of unknown origin and chronic sinusitis despite multiple courses of antibiotics. He underwent extensive investigations, including workups for infections, chronic granulomatous diseases and malignancy. Nasal biopsies were performed twice under local anaesthesia, but did not show any evidence of malignancy. Eventually, the patient was diagnosed with natural killer (NK)/T-cell lymphoma, nasal variant, based on histopathological findings from harvested deep tissue obtained via functional endoscopic sinus surgery. This study highlights that, for patients presenting with pyrexia of unknown origin and nasal symptoms, NK/T-cell lymphoma must be considered as a differential diagnosis. Generous amounts of tissue should be harvested under general anaesthesia rather than limited tissue under local anaesthesia, in order to facilitate and ensure a definitive diagnosis.