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A 63-year-old woman presented with dyspepsia and gastric pain without B symptoms. She had been treated with methotrexate for 8 years for psoriatic arthritis. Endoscopy showed multiple gastric ulcers. Histological examination revealed submucosal infiltration by small- to medium-size lymphoid cells (panel A, original magnification ×40; panel B, original magnification ×400; hematoxylin and eosin stain) that were CD20⁺ (panel C, original magnification ×100; panel D, original magnification ×400; immunoperoxidase stain), CD5⁻, and CD23. Occasional large CD30⁺ cells were observed (panel E, arrow, original magnification ×400; immunoperoxidase stain). In situ hybridization showed numerous Epstein-Barr virus–positive (EBV⁺) lymphoid cells (panel F, original magnification ×200). Positron emission tomography/computed tomography revealed no pathological 18F-fluorodeoxyglucose uptake. EBV⁺ mucocutaneous ulcer (EBVMCU) was diagnosed. Methotrexate was stopped without improvement of the gastric ulcers. The patient received rituximab, achieving a complete remission.

EBVMCU is a polymorphic proliferation of EBV⁺ atypical B-cells that characteristically occurs in immunosuppressed patients, mostly in the oropharyngeal mucosa. EBVMCU has a morphological spectrum that may simulate diffuse large B-cell lymphoma or even classic Hodgkin lymphoma (in CD20⁻ cases). EBVMCU is usually characterized by spontaneous regression. However, rituximab may be required to induce remission, as in our patient. EBVMCU, a provisional entity of 2016 World Health Organization classification of lymphohematopoietic neoplasms, has been revised as distinct entity in the 2022 International Consensus Classification of mature lymphoid neoplasms.