Massive Gastric Diffuse Large B-Cell Lymphoma: A Rare Case of Aggressive Primary Refractory Disease

Abstract Diffuse large B-cell lymphoma (DLBCL) is the most common non-Hodgkin lymphoma. It accounts for 30% of all non-Hodgkin lymphomas and typically presents as nodal disease. However, up to 40% of patients initially present with extranodal involvement, most commonly in the gastrointestinal tract. Although “bulky disease” is defined as tumor size >7.5 cm, cases exceeding 20 cm are exceedingly rare. We report a massive 25 × 17 cm gastric DLBCL with transmural extension into the transverse colon and small bowel in a patient who demonstrated rapidly progressing disease that was refractory to multiple lines of treatment, including R-CHOP, R-ICE, and R-GemOx. A 45-year-old man with a history of gastric DLBCL diagnosed 1 year earlier presented with progressive abdominal distension, pain, intolerance to oral intake, and bilateral lower limb edema. He had completed eight cycles of R-CHOP, two cycles of R-ICE, and then four cycles of R-GEMOX, with the last cycle 3 weeks prior. On examination, the abdomen was distended, firm, and tender. Laboratory tests revealed anemia (hemoglobin 7 g/dL). Contrast-enhanced computed tomography showed a gastric mass from 25 × 17 cm, with peritoneal and nodal involvement, compression of adjacent viscera, and probable invasion of the transverse colon. The patient underwent exploratory laparotomy with distal gastrectomy, segmental colectomy, and small bowel resection. Postoperative histopathology confirmed DLBCL, NOS, CD20 positive. MYC, Bcl2, Bcl6, MUM1, and CD10 were all negative. The patient recovered well postoperatively and was planned for oncological assessment. This case highlights the aggressive biology of gastric DLBCL with extreme tumor bulk and colonic invasion, underscoring the limitations of standard chemotherapy in bulky, refractory disease, and the importance of multidisciplinary management.