Incidental simultaneous caecal adenocarcinoma with appendix lymphoma in chronic lymphocytic leukaemia.

Simultaneous occurrence of colonic adenocarcinoma and appendiceal lymphoma in a patient with chronic lymphocytic leukaemia (CLL) is exceedingly rare. This unique coexistence presents diagnostic and therapeutic challenges, particularly in elderly patients with comorbidities. We report an unusual case of caecal adenocarcinoma and diffuse large B-cell lymphoma (DLBCL) of the appendix in a patient with known CLL. An 87-year-old male with a known diagnosis of CLL presented with a suspected caecal mass on imaging. Colonoscopy revealed a polypoidal caecal lesion, and biopsy confirmed adenocarcinoma. He underwent laparoscopic right hemicolectomy. Histopathology revealed moderately differentiated adenocarcinoma (pT3N0M0) and synchronous DLBCL in the appendix and mesenteric nodes, consistent with Richter's transformation. The patient was restarted on ibrutinib postoperatively. At 1.5 years, he developed an anastomotic recurrence managed with laparoscopic re-resection. He remains disease-free 3 years post-index surgery under multidisciplinary follow-up. This case highlights the importance of considering dual pathology in CLL patients presenting with gastrointestinal symptoms. Curative surgical resection, combined with targeted haematological therapy and regular surveillance, can result in favourable outcomes even in elderly patients with complex malignancies.