A rare case of primary testicular follicular lymphoma in a pediatric patient.

Testicular follicular lymphoma (TFL) is an exceedingly rare lymphoma that typically occurs in young male patients and is now recognized as a distinct diagnostic entity in the International Consensus Classification. TFL shows some clinicopathologic and genetic overlap with pediatric-type follicular lymphoma (PTFL). We report a case of TFL occurring in an otherwise healthy 4-year-old boy who presented with painless scrotal swelling. Orchiectomy revealed a 1.5-cm left testicular mass. Histologic sections showed a dense lymphoid infiltrate with nodular/follicular architecture growing between the seminiferous tubules. The infiltrate was composed of CD20/PAX5-positive B-cells that coexpressed germinal center markers (CD10, BCL6, MEF2B); they were negative for BCL2. No BCL2 or BCL6 rearrangements and no TNFRSF14 deletion were detected by FISH. Chromosomal microarray analysis detected copy-neutral loss of heterozygosity (CN-LOH) at 1p36.33-p36.32 (region of TNFRSF14). Next-generation sequencing detected variants in GNA13, RHOA, and TNFRSF14. In conclusion, this case shows the classic clinical, pathologic, and genetic features of TFL and highlights the similarities to PTFL and the importance of distinguishing this entity from other subtypes of FL. Patients with TFL typically respond favorably to orchiectomy and chemotherapy and have excellent clinical outcomes.