Marginal Zone Lymphomas

Marginal zone lymphoma (MZL) encompasses a heterogeneous group of small B-cell lymphomas, characterized by a predominance of tumor cells with a phenotype, homing pattern, and occasionally the appearance of the nonneoplastic marginal zone B cells that surround germinal centers and populate the white pulp of the spleen. Covered in this chapter are extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma), nodal marginal zone lymphoma (NMZL), and splenic B-cell marginal zone lymphoma (SMZL). Although the different subtypes of MZL share histologic and immunophenotypic features, they have divergent etiologies, molecular genetics, and clinical presentations. The pathogeneses of NMZL and SMZL are not yet clearly understood. The relationship of SMZL to hairy cell leukemia (HCL) and HCL-variant (HCL-v) is also discussed.