Rare non-Hodgkin lymphoma occurring in children
Low- or intermediate-grade mature B-cell lymphomas, such as small lymphocytic lymphoma, MALT lymphoma, mantle cell lymphoma, myeloma, or follicular cell lymphoma, are rarely seen in children. The most recent WHO classification has identified pediatric follicular lymphoma (FL) and pediatric nodal marginal zone lymphoma as unique entities.
Pediatric follicular lymphoma is a disease that differs from the adult counterpart genetically and clinically. The genetic hallmark of adult FL, the translocation of t(14;18)(q32;q21), is typically not detectable in pediatric FL. The outcome of pediatric FL is excellent, and in contrast to adult FL, the clinical course is not dominated by relapses, if the BFM protocols for DLBCL and BL are used. In pediatric FL, a simultaneous DLBCL can frequently be detected at initial diagnosis but does not indicate a more aggressive clinical course in children.[48,49]
Other diseases appear to reflect the disease observed in adult patients. For example, MALT lymphomas observed in pediatric patients usually present as low-stage (stage I or II) disease and are associated with H. pylori and require no more than local therapy involving curative surgery and/or radiation therapy.
Other types of NHL may be rare in adults and are exceedingly rare in pediatric patients, such as primary cutaneous lymphoma and PCNSL. Due to small numbers, it is difficult to ascertain if the disease observed in children is the same as in adults and, therefore, it is difficult to determine optimal therapy. Reports suggest that the outcome of pediatric patients with PCNSL may be superior to that of adults with PCNSL. These reports suggest that long-term survival can be achieved without cranial irradiation.[51,52,53] One report showed that most of the children had DLBCL or ALCL. Results of this study showed that therapy with high-dose intravenous methotrexate and cytosine arabinoside was most successful and that intrathecal chemotherapy may be needed only when malignant cells are present in the cerebral spinal fluid. There is a case report of repeated doses of rituxumab, both intravenous and intraventricular, being administered to a 14-year-old boy with refractory PCNSL, with an excellent result. This apparently good outcome needs to be confirmed especially since similar results have not been observed in adults.
Peripheral T-cell lymphoma (PTCL), excluding ALCL, is very rare in children. Mature T-cell/NK-cell lymphoma or PTCL has a postthymic phenotype (e.g., TdT negative), usually expresses CD4 or CD8, and has rearrangement of T-cell receptor (TCR) genes, either alpha/beta and/or gamma/delta chains. The most common phenotype observed in children is PTCL-not otherwise specified (NOS), although angioimmunoblastic lymphoma (AITL), enteropathy-associated lymphoma (EATL) (associated with celiac disease), subcutaneous panniculitis-like lymphoma, angiocentric lymphoma, and extranodal NK/T-cell PTCL have been reported.[55,56,57] Mycosis fungoides has rarely been reported in children and adolescents. Though very rare, hepatosplenic T-cell lymphoma is associated with children and adolescents who have Crohn disease and has been fatal in all cases. Optimal therapy for PTCL is unclear, even for adult patients. There have been two retrospective analyses of treatment and outcome for pediatric patients with PTCL. The United Kingdom Children's Cancer Study Group (UKCCSG) reported on 25 children diagnosed over a 20-year period with PTCL, with an approximate 50% 5-year survival rate. The UKCCSG also observed that the use of ALL-like therapy, instead of NHL therapy, produced a superior outcome. The Children's Oncology Group (COG) reported 20 patients older than 8 years treated on Pediatric Oncology Group NHL trials. Eight of ten patients with low-stage disease achieved long-term disease-free survival compared to only four of ten patients with high-stage disease.