S3690 Recurrent Extranodal Diffuse Large B-Cell Lymphoma Presenting as a Cecal Mass Over a Decade After Remission

Introduction: Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of non-Hodgkin lymphoma, with extranodal involvement occurring in up to 40% of cases. However, involvement of the colon and retro-peritoneum remains rare. Case Description/Methods: A 70-year-old woman with a history of DLBCL in remission presented with progressive weight loss, early satiety, and urinary frequency. Cross-sectional imaging revealed a large cecal mass with retroperitoneal extension causing urinary tract obstruction. Colonoscopy demonstrated a bulky, circumferential, partially obstructing infiltrative mass in the distal ascending colon. Histopathologic examination showed medium-to-large lymphoid cells with vesicular chromatin and small nucleoli. Immunohistochemistry was positive for CD20, CD45, and Bcl-2, with partial expression of Bcl-6 in approximately one-third of cells—findings consistent with a germinal center B-cell (GCB) phenotype. Bone marrow biopsy was negative for disease involvement. Discussion: Extranodal involvement is relatively common in DLBCL, but primary colorectal lymphoma is rare, with colonic involvement seen in only 20–40% of gastrointestinal lymphoma cases. This patient’s presentation, with a cecal mass, gastrointestinal symptoms, and urinary tract obstruction due to retroperitoneal invasion, highlights the aggressive nature of recurrent DLBCL and the importance of tailored treatment strategies in high-risk populations. The GCB phenotype observed in this case (CD20+, Bcl-2+, partial Bcl-6+, CD10-, MUM1-) is associated with a more favorable prognosis compared to the activated B-cell (ABC) subtype. Management in this case was complicated by the patient's prior exposure to R-CHOP chemotherapy, the standard frontline regimen for DLBCL, particularly due to the cumulative cardiotoxicity of doxorubicin. Given her frailty and hypoalbuminemia, dose reduction was necessary, in accordance with treatment modifications typically recommended for elderly or medically complex patients. This case highlights an unusual presentation of recurrent DLBCL involving the colon, underscoring the importance of considering lymphoma in the differential diagnosis of atypical gastrointestinal and genitourinary symptoms. It also emphasizes the value of individualized treatment planning in patients with prior chemotherapy exposure and comorbidities. Ongoing surveillance remains essential, as late relapse can occur even after prolonged disease remission.