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Morphologic and cytochemical characteristics of acute promyelocytic leukemia
F R Davey1, R B Davis, J M MacCallum
1Cancer and Leukemia Group B, Brookline, Massachusetts.
Abstract:
The existence of two distinct subtypes of acute promyelocytic leukemia was confirmed and characterized based on morphologic features of leukemic cells in a series of 63 patients studied by the Cancer and Leukemia Group B (CALGB). Seventeen patients (27%) had microgranular leukemic cells (M3V), and 46 patients (73%) had hypergranular leukemic cells (M3). These patient cohorts were studied for other laboratory and clinical features. Leukemic cells from M3V patients stained less frequently than leukemic cells from M3 patients for myeloperoxidase (median, 93% vs. 99%; P = .006), periodic acid-Schiff (median, 57% vs. 92%; P = .0001), ASD-chloroacetate esterase (median, 45% vs. 87%; P less than .0001), and alpha-naphthyl acetate esterase (0% vs. 37%; P = .0003). Patients with M3V had a higher platelet count (median, 50 vs. 30 x 10(9)/L; P = .01) and tended to have a higher leukocyte count (median, 7.4 vs. 2.2 x 10(9)/L; P = .06) than M3 patients. The patients with M3V morphology were more likely to be nonwhite (29% vs. 7%; P = .03), female (71% vs. 37%; P = .02), and to be infected at the time of presentation (71% vs. 35%; P = .02). No differences in the frequency of the t(15;17) karyotype or the immunophenotypic expression of the leukemic cells were noted in the two morphologic subtypes of acute promyelocytic leukemia. Fewer patients with M3V tended to enter complete remission (65% vs. 80%; P = .20), but no significant differences were found in the duration of complete remission (P = .81; 1 year rate, 50% vs. 85%), or probability of survival (P = .67; 1 year rate, 49% vs. 68%).
Insights
This study confirms two subtypes of acute promyelocytic leukemia (APL): microgranular (M3V) and hypergranular (M3). M3V APL patients showed distinct laboratory and clinical features, though outcomes were similar.
Area of Science:
- Hematology
- Oncology
- Leukemia Research
Background:
- Acute promyelocytic leukemia (APL) is a distinct subtype of acute myeloid leukemia.
- Morphological classification of APL has historically identified hypergranular (M3) and microgranular (M3V) variants.
- Understanding the differences between these subtypes is crucial for diagnosis and treatment.
Purpose of the Study:
- To confirm and characterize the two distinct subtypes of acute promyelocytic leukemia (M3V and M3) based on leukemic cell morphology.
- To compare laboratory and clinical features between M3V and M3 APL patient cohorts.
- To investigate potential differences in treatment response and survival between the subtypes.
Main Methods:
- Morphological analysis of leukemic cells from 63 acute promyelocytic leukemia patients.
- Comparison of laboratory markers including myeloperoxidase, periodic acid-Schiff, esterase stains, platelet count, and leukocyte count.
- Analysis of clinical characteristics such as race, sex, infection status, and treatment outcomes (remission, duration, survival).
Main Results:
- Seventeen patients (27%) presented with microgranular APL (M3V), while 46 (73%) had hypergranular APL (M3).
- M3V leukemic cells showed significantly lower staining for myeloperoxidase and various esterases compared to M3 cells.
- M3V patients had higher platelet counts and were more likely to be nonwhite, female, and infected at presentation.
- No differences were observed in the t(15;17) karyotype or immunophenotypic expression between the subtypes.
- While M3V patients tended towards lower complete remission rates, no significant differences in remission duration or survival were found.
Conclusions:
- The study confirms the existence of two distinct morphological subtypes of acute promyelocytic leukemia: M3V and M3.
- Significant differences in laboratory and demographic features exist between M3V and M3 APL.
- Despite morphological and some clinical variations, the overall treatment outcomes and survival probabilities appear similar for both subtypes.