[A study on the relationship between morphology and gene heterogeneity in acute promyelocytic leukemia]

Aucte promyelocytic leukemia (APL) can be treated by all-trans retinoic acid (ATRA) with high complete remission rate. 50 cases of APL diagnosed morphologically were studied on their cytogenetics, molecular biology and response to treatment with ATRA. Forty-five cases showed chromosomal translocation t(15; 17) and PML/RAR alpha fusion gene (PML + RAR alpha + APL). They had typical morphologic change, in which hypergranular cells appeared more frequently in L type of PML/RAR alpha and microgranular cells in S type of PML/RAR alpha. Among the 45 PML + RAR alpha + APL patients 8 died early and 37 had complete remission with ATRA. In the remainging 5 patients, three had typical APL morphologic features in cytology, but one of them displayed t (11; 17) with PLZF+RARA alpha +, the second showed RAR alpha + PML - (PML - RAR alpha + APL) and the third PML - RAR alpha -(PML - RAR alpha - APL). They did not respond to ATRA treatment. These data indicate that APL is not a homogeneous disease. The other a patients had neither chromosomal translocation nor rearrangements of the two genes. On careful morphological reexamination, these two cases were not APL, but one of them responded well to ATRA. It is shown that morphology is the important diagnostic basis of APL, but in a few APL cases diagnosis should be made with the help of cytogenetics and molecular biology. Response of ATRA treatment may be of diagnostic value of APL, but is not a specific criterion.