Testicular Relapse of Primary Diffuse Large B-cell Lymphoma of the Central Nervous System - a Rare Occurrence.

Among diffuse large b-cell lymphoma (DLBCL) subtypes, primary testicular lymphoma (PTL) has one of the highest risks of central nervous system (CNS) relapse. The converse, primary CNS lymphoma (PCNSL) relapse outside the CNS is rare. Molecular analysis has illustrated a genetic similarity between PTL and PCNSL. Here we present a case of a 64-year-old man with testicular relapse of PCNSL 20 months after a complete response to high dose methotrexate-based chemotherapy. His tumor demonstrated a molecular profile similar to both PCNSL and PTL on next generation sequencing, and molecular analysis confirmed common clonal origin of his CNS and testicular lesions. We review prior cases of testicular relapse of PCNSL, which lacked molecular investigations, and discuss the implications of the genomic findings in our patient, including future treatment options.