Challenges in Diagnosing Non-Nasal Natural Killer/T-Cell Lymphoma Mimicking Behçet Disease: A Case Report

BACKGROUND Natural killer/T-cell lymphoma (NKTL) represents a distinct subtype of non-Hodgkin lymphoma associated with Epstein-Barr virus infection. NKTLs can be classified into nasal or non-nasal forms, which differ substantially in clinical, pathophysiological, and genetic features. Non-nasal-type NKTL and Behçet disease share overlapping clinical manifestations, including recurrent ulcerations, unexplained fever, abdominal pain, and other systemic symptoms. Distinguishing between these 2 diseases poses a significant challenge in clinical practice. This report describes a patient with non-nasal-type NKTL that was initially misdiagnosed as Behçet's disease, resulting in missed optimal therapeutic intervention. CASE REPORT A 45-year-old man had been suffering from recurrent oral ulcerations accompanied by odynophagia, dysphagia, and genital ulcerations for 1 month. During the first hospitalization, the patient was initially diagnosed with Behçet disease and achieved symptomatic remission following corticosteroid therapy. However, despite regular glucocorticoid therapy, within 3 months, symptoms recurred, with disease progression manifesting as larger oral ulcers, recurrent fever, and gastrointestinal hemorrhage. Further refined serological, imaging, and bone marrow aspiration cytology examinations did not yield a definitive diagnosis. The diagnosis of NKTL was finally established through histopathological examination of concurrent oral and ileocecal ulcer biopsies. However, the patient declined further antitumor therapy and was discharged against medical advice. CONCLUSIONS When recurrent mucocutaneous lesions co-occur with systemic symptoms suggestive of lymphoma, it is critical to pursue early mucosal and bone marrow biopsies to ensure accurate diagnosis and avoid mismanagement. Enhanced clinical vigilance and thorough pathological assessment are essential to distinguish mimicking conditions and initiate timely treatment.