Marginal zone lymphoma (MZL) is a rare, slow-growing cancer of the lymphatic system that develops from a type of blood cell called a B lymphocyte. There are three distinct types of MZL - mucosa-associated lymphoid tissue (MALT) lymphoma, nodal MZL, and splenic MZL. Although MZL cannot be cured, there are effective treatments available and some people can live with MZL for many years.