Pediatric follicular lymphoma--a clinico-pathological study of a population-based series of patients treated within the Non-Hodgkin's Lymphoma--Berlin-Frankfurt-Munster (NHL-BFM) multicenter trials

Abstract

Background Pediatric follicular lymphoma has recently been recognized as a novel variant of follicular lymphoma in the World Health Organization classification of lymphomas. Given the rarity of the disease, histopathological and genetic data on this type of lymphoma are still scarce.

Design and methods: We analyzed 25 cases of pediatric follicular lymphoma (patients aged <or=18 years) by morphology, immunohistochemistry and interphase fluorescence in situ hybridization. All patients analyzed were treated within Non-Hodgkin's Lymphoma--Berlin-Frankfurt-Münster (NHL-BFM) multicenter trials, and the cohort was representative of the German population.

Results: The genetic hallmark of adult follicular lymphoma, t(14;18)(q32;q21), was not detectable in any of the pediatric cases, although BCL2 protein was expressed in 55% of the latter cases. No correlation was found between BCL2 protein expression and outcome. Chromosomal breaks in the immunoglobulin heavy chain gene (IGH) and the BCL6 locus were detected in 5 of 17 and 1 of 18 cases, respectively. Patients with pediatric follicular lymphoma had long event-free survival and, in contrast to adult follicular lymphoma, the clinical course was not dominated by relapses. A simultaneous diffuse large B-cell lymphoma was frequently detected at initial diagnosis in children but did not indicate an aggressive clinical course. Conclusions Our data suggest that pediatric follicular lymphoma is a disease that differs from its adult counterpart both genetically and clinically.

Figure 1.

Follicular lymphoma grade 3a involving the tonsil (A) with a simultanous DLBCL component in deeper parts of the tumor (B) with higher magnification in the inserts, (A+B Giemsa stain). Strong expression of BCL2 (C) in the absence of BCL2 breaks (insert in C) and dense networks of follicular dendritic cells positive for CD23 (D), A-D correspond to case 5 in Tables 1 and 2). A floral follicular growth pattern in case 12 highlighted by staining for CD10 (E). Breaks in the IGH gene of case 13 (F, arrows indicate the split signal).