Cytogenetic findings in acute promyelocytic leukaemia. A report of 25 cases.

Cytogenetic analyses of bone marrow cells were carried out by means of direct technique and short-term cultures in 25 acute promyelocytic leukaemia (APL) patients. 16 were affected by the hypergranular form and 9 by the M3-variant. The t(15;17) was documented at diagnosis in 15 patients. In addition, 2 cases, in which an M3 morphology and a normal karyotype on direct preparation were found at diagnosis, disclosed the chromosome anomaly in cultured cells at relapse, in concomitance with a change of blast morphology to the M3-variant. However, the t(15;17) was a consistent feature in 5 of the 15 patients with cells analysed on direct preparations only and in all cases who had successful bone marrow cultures. Overall, the 15;17 translocation was detected in 7 out of 9 patients with the M3-variant and in 8 out of 16 patients with typical M3. Whenever the chromosome preparations were made after culture, 7/7 had the translocation in the M3-V group and 5/5 in the M3 group. No obvious differences in clinical features or outcome were evident in the patients, irrespective of their cytogenetic findings.