Acute promyelocytic leukemia (APL) accounts for 10 to 15% of acute myeloid leukemias (AML). This type of leukemia (AML-M3 according to the FAB classification) is associated, in about 90% of the cases, with a t(15;17)(q22;q21) translocation, resulting in the fusion of the PML and RARalpha genes. Traditional cytogenetic analysis has been used to confirm the morphological diagnosis of ALP. Although the t(15;17) translocation is characteristic for this kind of leukemia, "false-negative" results may occur as a result of the analysis of cells which do not belong to the neoplastic clone, of the difficulty to visualize the translocation and even of the existence of cryptic rearrangements masking the translocation. Moreover, alternative chromosome alterations were described in patients with APL and in these cases treatment with ATRA is not effective. From July 1993 to December 2002, 47 cases suspected of or being diagnosed with APL by clinical-laboratorial methods were referred for cytogenetic analysis. Thirty-four patients (72.3%) had the t(15;17) translocation, detected by traditional and/or molecular cytogenetics. In six of these patients, additional chromosome alterations or rearrangements involving a third chromosome were observed. In five patients (10%) with APL characteristics, the FISH technique did not reveal the PML/RARalpha fusion, an important finding in the process of reaching a diagnosis and of establishing a therapeutic conduct for these patients. This work was carried out with the purpose of evaluating the importance of traditional and molecular cytogenetic analysis in the diagnosis of APL.
Leukemia promyelocytic acute; cytogenetic analysis; fluorescent in situ hybridization (FISH)
