HIGH-DEGREE OF MYELOID DIFFERENTIATION AND GRANULOCYTOSIS IS ASSOCIATED WITH T(8-21) SMOLDERING LEUKEMIA

The t(8;21) is a frequent chromosome abnormality in acute myeloid leuk emia (AML), particularly associated with M2 of the French-American-Bri tish (FAB) classification, but also found in a few patients with myelo dysplastic syndrome (MDS). The two genes involved in the t(8;21) have been recently isolated and the cDNA of the AML1/ETO fusion gene identi fied. We have investigated a series of AML and MDS patients by a rever se transcriptase-polymerase chain reaction (RT-PCR) and analyzed the c linical and laboratory features of leukemia with t(8;21). The t(8;21) was only found in a subset of M2, which had the clinical and hematolog ical features distinct from those M2 without t(8;21). M2 with t(8;21) was associated with a significantly higher myeloid differentiation and with a good response to chemotherapy. Moreover, among the patients wi th refractory anemia with excess of blasts in transformation (RAEB-T) the t(8;21) was also significantly associated with a higher myeloid di fferentiation and a good response to chemotherapy. M2 patients with t( 8;21) could be distinguished on a number of hematological parameters, eg white blood cell count and percentage of bone marrow myeloblasts an d promyelocytes, from RAEB-T carrying the t(8;21). Based on these find ings we suggest that leukemia patients carrying t(8;21) can be grouped into two types: overt acute myeloid leukemia (M2) and smoldering or s lowly evolving myeloid leukemia.