MYD88 and primary central nervous system lymphoma: In the present study, we conducted a multi-institutional study to diagnose and initiate treatment for PCNSL by liquid biopsy alone without a surgical biopsy.<h4>Methods</h4>We analyzed 10 patients from 5 institutions who were deemed difficult to biopsy surgically and were subsequently treated based on the detection of <i>MYD88</i> L265P-mutant droplets in their CSF cfDNA.