Pediatric follicular lymphomas, marginal zone lymphomas, and marginal zone hyperplasia.

Whereas most B-cell lymphomas in children are of diffuse large B-cell or Burkitt type, other B-cell lymphomas, including follicular and marginal zone B-cell lymphomas, rarely occur Pediatric follicular lymphomas (FLs) have many features indistinguishable from those seen in adults but demonstrate an increased proportion that are localized, lack bcl-2 protein expression, lack bcl-2 translocations, and are grade 3 but still indolent. They also tend to have large expansile follicles. Although usually at nodal or tonsillar sites, other extranodal involvement also occurs, with FL of the testis well described. Distinction from potentially clonal but reactive follicular hyperplasia is important. Marginal zone B-cell lymphomas of nodal and extranodal types are other indolent B-cell neoplasms that usually are seen in adults but also occur in children. The differential diagnosis must include the very recently reported lambda light chain class-restricted marginal zone hyperplasias of the tonsil or appendix that might closely mimic a lymphoma. Understanding the full spectrum of B-cell neoplasia in children and its unique features is important for diagnostic, therapeutic, and academic purposes.