Testicular large B-cell lymphoma is genetically similar to PCNSL and distinct from nodal DLBCL

Testicular large B-cell lymphoma (TLBCL) is an infrequent and aggressive lymphoma arising in an immune-privileged site and has recently been recognized as a distinct entity from diffuse large B-cell lymphoma (DLBCL). We describe the genetic features of TLBCL and compare them with published series of nodal DLBCL and primary large B-cell lymphomas of the CNS (PCNSL). We collected 61 patients with TLBCL. We performed targeted next-generation sequencing, copy number arrays, and fluorescent in situ hybridization to assess chromosomal rearrangements in 40 cases with available material. Seventy percent of the cases showed localized stages. BCL6 rearrangements were detected in 36% of cases, and no concomitant BCL2 and MYC rearrangements were found. TLBCL had fewer copy number alterations (p < 0.04) but more somatic variants (p < 0.02) than nodal DLBCL and had more frequent 18q21.32-q23 (BCL2) gains and 6q and 9p21.3 (CDKN2A/B) deletions. PIM1, MYD88^L265P, CD79B, TBL1XR1, MEF2B, CIITA, EP300, and ETV6 mutations were more frequent in TLBCL, and BCL10 mutations in nodal DLBCL. There were no major genetic differences between TLBCL and PCNSL. Localized or disseminated TLBCL displayed similar genomic profiles. Using LymphGen, the majority of cases were classified as MCD. However, we observed a subgroup of patients classified as BN2, both in localized and disseminated TLBCL, suggesting a degree of genetic heterogeneity in the TLBCL genetic profile. TLBCL has a distinctive genetic profile similar to PCNSL, supporting its recognition as a separate entity from DLBCL and might provide information to devise targeted therapeutic approaches.