Low grade lymphomas are rare in children but two entities have been described in the WHO classification paediatric follicular lymphoma and paediatric nodal marginal zone lymphoma.
Paediatric Follicular Lymphoma
Paediatric follicular lymphoma is distinct from the common adult variety genetically and clinically. The differences include
- Patients of the paediatric folliculr lymphoma lack the t(14;18)(q32;q21) translocation and the bcl-2 activation that is the genetic hallmark of the adult follicular lymphoma. Expression of bcl2 in pediatric follicular lymphoma is associated with a poor outcome (Blood March 15, 2002vol. 99 no. 6 1959-1964)
- Paediatric follicular lymphoma is a localized disease adult follicular lymphoma is disseminated at presentation
- Paediatric follicular laymphomas have a better outcome than adult follicular lymphoma. This is despite the fact that pediatric patients have higher morphological grade (predominantly grade 3A). They may have a associated diffuse components but this dies not affect the outcome of treatment. Patients may be cured by local excision.
Paediatric Nodal Marginal Zone Lymphoma (pNMZL)
Peadiatric nodal marginal zone lymphoma presents with asymtomatic localized (usually stage I) disease usually in the neck region in males (M:F 20:1). The histology and immunophenotype is similar to that of adults. The outcome of pNMZL is excellent and relapses are exceedingly rare. Two adults with pNMZL have recently been described (Leuk Lymphoma. 2010 January; 51(1): 89–94).
Other B and T low grade lymphomas have been described in children. These are very rare and the natural history does not appear to be different from adults.