Extranodal natural killer-cell lymphoma presenting to the emergency room with abdominal pain: a case report.

BACKGROUND

Extranodal natural killer (NK)/T-cell lymphoma, nasal type (ENKL), is a rare and aggressive Epstein-Barr virus (EBV)-associated non-Hodgkin lymphoma with a predilection for extranodal sites. Primary gastrointestinal involvement is exceedingly uncommon, accounting for < 1% of all malignant lymphomas, and often presents with nonspecific symptoms. Perforation is rare but is associated with dismal outcomes.

CASE PRESENTATION: A previously healthy Japanese male patient, aged 20-year-old male developed sudden-onset abdominal pain and an episode of bloody stool. On admission, he was febrile and tachypneic but hemodynamically stable. Physical examination revealed lower abdominal tenderness without peritoneal signs, and laboratory tests showed only a slight elevation in inflammatory markers. Contrast-enhanced abdominal computed tomography (CT) revealed no abnormalities. Despite analgesic administration, the pain persisted, necessitating hospitalization. On hospital day 2, repeat CT revealed intraperitoneal free air, prompting emergency laparotomy. Intraoperatively, a perforated ileal lesion with semi-circumferential ulceration was identified 100 cm proximal to the terminal ileum, and partial resection was performed. Histopathology and immunohistochemistry confirmed ENKL (EBV-encoded RNA-positive, CD3 positive, CD20 negative). Postoperatively, the patient received two cycles of SMILE (dexamethasone, methotrexate, ifosfamide, l-asparaginase, and etoposide) chemotherapy. During hematopoietic recovery, he developed EBV-related hemophagocytic lymphohistiocytosis with acute liver failure. Despite intensive treatment, the patient died within 3 months of presentation.

CONCLUSION

This case highlights the diagnostic challenge of primary gastrointestinal ENKL in patients presenting with abdominal pain and hematochezia in the absence of computed tomography (CT) abnormalities. Persistent unexplained abdominal pain should prompt consideration of rare ulcerative small bowel diseases, including ENKL, particularly when perforation is a potential complication. Early multidisciplinary intervention is essential to improve the outcomes of this devastating condition.