CD79B and MYD88 mutations are the hallmark of PCNSL [15], and in this study, although only one tumor tissue sample was available, MYD88L265P can be detected in both CSF cfDNA and tumor tissue, with similar VAFs, so this suggests that CSF cfDNA reflects the genomic information of a tumor to some degree and might play a role in the diagnosis of CNSL. Here, CD79B is linked to primary central nervous system lymphoma.