Nickan Research Institute Immunopathologia Persa 2423-8015 10 1 2024 01 01 Duodenal monomorphic epitheliotropic intestinal T cell lymphoma along with unpredictable intestinal Epstein-Barr virus infection; a rare newly redefined entity in a rare site and review of literature e25261 e25261 10.34172/ipp.2022.25261 EN Somaia Ahmed Saad El-Din https://orcid.org/0000-0001-9729-0857 Khalid Al Hashmi Khaled Hamad Fahad Al-Ghafri Journal Article 10.34172/ipp.2022.25261 2021 04 25 2021 07 10 Introduction: Monomorphic epitheliotropic intestinal T-cell lymphoma (MEITL), previously known as type II enteropathy associated T-cell lymphoma (EATL), was redefined by the WHO (2016) as separate entity from the celiac disease-associated lymphoma. It is an extremely rare and highly aggressive peripheral T-cell lymphoma. It mainly involves jejunum and ileum and rarely duodenum. Case Presentation: This was a 38-year-old male patient presented by daily vomiting related to meals for 8 months along with generalized colicky abdominal pain associated with constipation and marked weight loss. Upper endoscopy showed large ulcerated mass at the third part of the duodenum. Histopathological examination showed the diffuse malignant lymphoid infiltrate with morphology and immunophenotyping consistent with MEITL associated with unpredictable Epstein-Barr virus (EBV) in intestinal epithelial cells. The patient underwent five cycles of chemotherapy (cyclophosphamide, hydroxydaunorubicin, oncovin and prednisone) followed by duodenectomy. Conclusion: This case represents a rare newly redefined lymphoma entity in a rare site associated with unpredictable non-neoplastic epithelial EBV infection, which proved to be oncogenic agent involved in various hematopoietic and other neoplasms with unclear relationship to the development of this MEITL.