CD5-positive diffuse large B-Cell lymphoma presenting with protein-losing enteropathy.

Primary gastrointestinal lymphoma accounts for only 1-4% of all gastrointestinal malignancies, yet the gastrointestinal tract is the most common extranodal site of non-Hodgkin lymphoma, comprising 10-15% of all non-Hodgkin lymphomas. Among these, diffuse large B-cell lymphoma (DLBCL) and mucosa-associated lymphoid tissue lymphoma frequently affect the stomach and small intestine. Protein-losing enteropathy associated with malignant lymphoma is exceedingly rare, particularly when caused by CD5-positive DLBCL. We report the case of a 60-year-old woman with a four-year history of refractory diarrhea and progressive lower extremity edema, ultimately diagnosed with CD5-positive DLBCL of the small intestine. Diagnostic workup revealed hypoproteinemia with significant protein leakage in the ascending colon and distal small intestine. Double-balloon endoscopy demonstrated shallow, wide ulcers with patchy whitish exudates, and histopathology confirmed a diagnosis of de novo CD5-positive DLBCL. Chemotherapy with rituximab, etoposide, prednisolone, vincristine, cyclophosphamide, and doxorubicin (DA-EPOCH-R) led to prompt improvement in serum albumin levels and resolution of the protein-losing enteropathy. Subsequent high-dose chemotherapy with autologous stem cell transplantation has maintained remission. Given the rarity of this presentation and its strong similarity to a previously reported case of CD5-positive DLBCL with protein-losing enteropathy, we propose that this might represent a distinct clinical entity.