“…Among ALL relapses, approximately 20-40% occur in the CNS, either isolated or combined with bone marrow involvement. 29 Conventional cytologic (CC) analysis represents the mainstay of CSF analysis for ALL but, similar to the morphological evaluation of the bone marrow, offers limited sensitivity for leukemic detection. Applying MRD to standard CSF analyses may offer additional clinical value and has been the subject of several studies in pediatric and adult ALL.…”