Mosunetuzumab in Patients With Newly Diagnosed Extranodal Marginal Zone Lymphoma

This study tests mosunetuzumab, a bispecific antibody that redirects the immune system to attack lymphoma cells, in patients with newly diagnosed extranodal marginal zone lymphoma (EMZL) — a slow-growing type of blood cancer that starts in tissues outside lymph nodes (like the stomach, eyes, or salivary glands). **You may be eligible if:** - You are 18 or older with confirmed extranodal marginal zone lymphoma (EMZL) at any stage - You have not previously received systemic (whole-body) treatment for EMZL - You have at least one tumor that can be measured on imaging - You are able to comply with the study schedule - Special case: If you had stomach EMZL caused by H. pylori bacteria and were treated with antibiotics, you may still be eligible if lymphoma is confirmed on biopsy after antibiotic treatment **You may NOT be eligible if:** - You have already received systemic therapy for EMZL - Your lymphoma cannot be measured on imaging - You are not able to comply with study visits and procedures Talk to your doctor to see if this trial is right for you.