Diffuse Large B-cell Lymphoma Developing on the Background of Long-standing Ulcerative Colitis: A Case Report.

Ulcerative colitis (UC) is a chronic inflammatory bowel disease that may result in malignant complications over time, though lymphoma is rarely reported. This paper describes a 46-year-old woman with an eight-year history of UC who was admitted with acute severe ulcerative colitis based on the Truelove and Witts criteria. She initially improved with intravenous corticosteroids, but hematochezia recurred during tapering. A cytomegalovirus infection was confirmed by PCR and treated with ganciclovir, resulting in partial symptom relief. Repeated colonic biopsies were obtained because of persistent bleeding. A histological examination revealed atypical lymphoid infiltration, and immunohistochemical staining confirmed the diagnosis of diffuse large B-cell lymphoma arising on the background of long-standing UC. The diagnosis led to a major change in management, shifting from the planned initiation of infliximab to systemic chemotherapy. This case emphasizes the importance of considering lymphoma as a rare but serious complication in patients with chronic UC, particularly in those with atypical or partially responsive disease courses. Thorough histopathological evaluations, including immunohistochemistry, are crucial for preventing misdiagnoses and ensuring safe and effective treatment decisions.