Lymphoblast morphology in predicting leukemic meningeal relapse with low chamber count and lymphoblasts

The diagnostic criteria for meningeal relapse (MR) of acute lymphoblastic leukemia (ALL) are a cerebrospinal fluid (CSF) chamber count of more than five leukocytes per microliter and a cytomorphological evaluation revealing lymphoblasts. A dilemma arises when confronted with a patient with a low CSF white blood cell (WBC) chamber count and lymphoblasts. We utilized a scoring system to review lymphoblast morphology in 12 such patients. A cell was defined as a lymphoblast if it could not be easily categorized as a lymphocyte, monocyte. histiocyte, or granulocyte. Each lymphoblast was scored on four parameters: presence of nucleoli, homogeneous distribution of chromatin, nucleocytoplasmic ratio greater than 75%, and nuclear irregularity. Cells were scored without knowledge of the patients' out come. Seven patients eventually developed MR by current criteria and five patients never relapsed. The mean lymphoblast scores for patients that did and did not relapse were 2.35 and 1.53, respectively (P < .001). The percent of cells scored as lymphoblasts was also significantly higher in patients that relapsed, 36.9% vs. 19.4% (P = .01). Our study shows that careful cytomorphologic analysis can predict which patients with low chamber counts and "blasts" on cytocentrifuge examination will progress to meningeal relapse. We recommend reviewing the definition of MR and using a scoring system when confronted with blasts in a low chamber count cerebrospinal fluid specimen.