[Analysis of Morphologic Classification System for Acute Promyelocytic Leukemia and Its Correlation with Laboratory Tests and FLT3-ITD Mutation].

Objective: To establish a morphologic classification system for characterizing blast cells in patients with acute promyelocytic leukemia (APL) and analyze the correlation of different APL morphologic characteristics with conventional tests and genetic variants.

Methods: Based on the morphological characteristics of APL blast cells, a classification system of 14 categories was established to characterize the inter- and intra-individual cellular morphological heterogeneity of patients. The classification system was used for the morphological analysis of 40 APL patients, and the classification results were statistically analyzed with the patients' conventional test indexes and gene variant characteristics to analyze the correlation of different APL blast cell morphological features with conventional test indexes and gene variants.

Results: In the FLT3-ITD mutation-positive group, there were significantly fewer cells with regular nuclear shape, hyper granularity, and missing Auer rods (category 1) than in the FLT3 mutation-negative group (P < 0.05). The activated partial thromboplastin (APTT) was significantly longer in the group with regular nucleus compared to the group with irregular nucleus (P < 0.05). In the hypo-granular group, the APTT was also significantly longer compared to the hyper-granular group (P < 0.01), and the proportion of myeloid blast cells was relatively lower (P < 0.05). The peripheral blood white blood cell counts, D-dimer, lactate dehydrogenase and proportion of bone marrow blast cells were significantly higher in the Auer rods (-) group than Auer rods increasing group (all P < 0.05).

Conclusion: The newly established morphologic classification system in this study can objectively characterize different types of APL blast cells, which helps to better assess the intra- and inter-individual heterogeneity of APL blast cells, and further use in accurately analyzing the correlation of morphological phenotypes with biological properties of APL.