Case report of extranodal NK/T-cell lymphoma mimicking Behcet syndrome

Rationale: Extranodal natural killer (NK)/T-cell lymphoma is an uncommon non-Hodgkin lymphoma, prevalent in Asia. It often involves the nasal and upper airway regions but can disseminate to other sites like skin, soft tissue, testis, and gastrointestinal tract, characterized by Epstein–Barr virus association. Patient concerns: This report discusses a 48-year-old male initially diagnosed with Behcet syndrome with dry mouth, uveitis, pruritic macules, and human leukocyte antigen-B51 positivity. Despite steroid treatment, a growing testicular mass and erythema nodosum led to reevaluation. Diagnoses: Biopsy confirmed Epstein–Barr virus-positive extranodal NK/T-cell lymphoma. The imaging indicated lymphoma spread to the nasal cavity, lymphatic chains, bones, and spleen. Interventions: The patient received multi-agent SMILE (methotrexate, ifosfamide, L-asparaginase, mesna, etoposide, dexamethasone) chemotherapy. Outcomes: The patient achieved a metabolic complete response after 2 cycles of SMILE chemotherapy. Lessons: This report highlights the diagnostic pitfalls due to symptoms and signs overlapping between Behcet syndrome and extranodal NK/T-cell lymphoma.