Would you consider a patient with DLBCL to have CNS involvement if no brain lesion is seen on imaging, CSF flow cytometry is negative, but PCR is positive for MYD88 and KMT2D mutations?  

Cerebrospinal fluid (CSF) is an ultrafiltrate of plasma contained within the ventricles of the brain and the subarachnoid spaces of the cranium and spine. It is possible that cfDNA fragments containing MYD88 and KMT2D mutations may have found their way into the CSF and thereby detected by PCR techn...