Primary follicular lymphoma of the testis in childhood: an entity with peculiar clinical and molecular characteristics.

Background/aims: Paediatric primary follicular lymphoma of the testis (PPFLT) is exceptional: the few reported cases seem to lack BCL-2 gene rearrangement and/or protein expression. The aim of this study was to characterise a PPFLT arising in a 4 year old boy.

Methods: This case was characterised using conventional histological analysis, immunohistochemistry, and a polymerase chain reaction based method for the detection of immunoglobulin V(H) chain rearrangements.

Results: The neoplasm was staged I(E)/A; left orchiectomy and chemotherapy were performed, producing complete remission. Histology showed a predominantly follicular lymphoid infiltrate mainly composed of centroblast-like cells. The phenotype was CD20(+), CD79a(+), CD10(+), bcl-6(+), B cell specific activating protein(+), kappa light chain(+), CD30(-/+), interferon regulating factor 4(-/+), c-myc(-/+), lambda light chain(-), CD3(-), bcl-2(-), p53(-), cytokeratin(-), and placental alkaline phosphatase(-). Lymphomatous elements were found within a CD21(+) follicular dendritic cell network and 70% were positive for Ki-67/MIB-1. Molecular analysis revealed monoclonal immunoglobulin heavy chain gene rearrangement and BCL-6 mutations, in the absence of BCL-2 major breakpoint and BCL-2 minor cluster region rearrangements, p53 mutations, and death associated protein kinase gene hypermethylation.

Conclusions: These findings suggest a different pathogenesis of PPTFL compared with adult follicular lymphoma and might explain its favourable course in spite of aggressive histology.