Table 2. Major Histopathological Categories of Non-Hodgkin Lymphoma in Children and Adolescentsa continued...
Pediatric follicular lymphoma is a disease that differs from the adult counterpart genetically and clinically. The genetic hallmark of adult follicular lymphoma, the translocation of t(14;18)(q32;q21) involving BCL2, is typically not detectable in pediatric follicular lymphoma.[50,51] Molecular alterations observed in pediatric follicular lymphoma include translocations of the immunoglobulin locus and IRF4, losses of regions of chromosome 1p, and mutations of TNFSFR14 on chromosome 1p.[32,52]
Pediatric follicular lymphoma predominantly occurs in males, is associated with a high proliferation rate, and is more likely to be localized disease. In contrast, adult follicular lymphoma usually presents as disseminated disease with a relatively low proliferation rate.[50,51,53] Cervical lymph nodes and tonsils are common sites, but disease has also occurred in extranodal sites such as the testis, kidney, gastrointestinal tract, and parotid.[50,51,53,54,55,56] The outcome of pediatric follicular lymphoma is excellent, and in contrast to adult follicular lymphoma, the clinical course is not dominated by relapses.[51,53,54] In pediatric follicular lymphoma, a simultaneous diffuse large B-cell lymphoma can frequently be detected at initial diagnosis but does not indicate a more aggressive clinical course in children.[53,55]
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 pediatric gastric MALT lymphomas are associated with Helicobacter pylori and require no more than local therapy involving curative surgery and/or radiation therapy. Conjunctival MALT lymphomas are often associated with chlamydial psittaci infections. Intralesional interferon-alpha for conjunctival MALT lymphoma has been described.
Other types of NHL may be rare in adults and are exceedingly rare in pediatric patients, such as primary CNS lymphoma. 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 primary CNS lymphoma (OS, 70%–80%) may be superior to that of adults with primary CNS lymphoma. These reports suggest that long-term survival can be achieved without cranial irradiation.[60,61,62,63] Most children have diffuse large B-cell lymphoma or anaplastic large cell lymphoma. Therapy with high-dose intravenous methotrexate and cytosine arabinoside is most successful and intrathecal chemotherapy may be needed only when malignant cells are present in the cerebral spinal fluid.[61,63] There is a case report of repeated doses of rituximab, both intravenous and intraventricular, being administered to a 14-year-old boy with refractory primary CNS lymphoma, with an excellent result. This apparently good outcome needs to be confirmed, especially since similar results have not been observed in adults. (Refer to the PDQ summary on Primary CNS Lymphoma Treatment for more information on treatment options for nonacquired immunodeficiency syndrome–related primary CNS lymphoma.)