Recurrent Composite Lymphoma in an Elderly Man: A Case of Marginal Zone Lymphoma With Classic Hodgkin Features Treated With Brentuximab and Immunotherapy.

Composite lymphoma (CL) is a rare and diagnostically challenging condition where two or more distinct types of lymphoma coexist within the same anatomical site. We report the case of an 82-year-old man with a history of low-grade B-cell lymphoma, now presenting with recurrent disease characterized by a composite histology of marginal zone lymphoma (MZL) and classic Hodgkin's lymphoma (CHL). Management involved single-agent brentuximab due to comorbidities, followed by immune checkpoint inhibition upon relapse. This case illustrates key considerations in the diagnosis, staging, and treatment of CLs in geriatric patients. The clinical course further highlights the importance of personalized therapy selection based on age, comorbidities, and histological features. This case also contributes to the limited literature on real-world outcomes in patients with CL and underscores the need for future prospective studies and biomarker-driven treatment approaches in this rare entity.