ACUTE LEUKEMIC TRANSFORMATION OF MYELODYSPLASTIC SYNDROME - IMMUNOPHENOTYPIC, GENOTYPIC, AND CYTOGENETIC STUDIES

The clinical and biological characteristics of myelodysplastic syndrom e (MDS) in acute leukemic transformation were studied in 23 patients. All had myeloid transformation according to FAB criteria, but coexpres sion of lymphoid-associated antigens was detected in five of the 20 pa tients who underwent an immunophenotypic study. Rearrangement of the i mmunoglobulin heavy chain gene was also observed in one of the five pa tients who coexpressed lymphoid markers and that of the T-cell recepto r beta chain gene in another one. None had pure lymphoid transformatio n. Clonal chromosomal abnormalities were noted in 12 (63%) of the 19 p atients who underwent cytogenetic study, most commonly -7 (six patient s or 32%). In the 18 patients who underwent serial analyses both at MD S diagnosis and at acute transformation, seven (39%) underwent karyoty pic evolution. The most common new or additional aberrations were +8 a nd +21. N-ras gene mutation was detected in two of the nine patients a t acute leukemic transformation. The median interval from diagnosis of MDS to onset of acute transformation was 10 months (1-36 months). Pat ients with a normal karyotype at diagnosis had a significantly longer chronic phase duration than those with chromosomal abnormalities (medi an of 20 months vs. 5 months). However, all had a short survival time after diagnosis of acute leukemia, whether chromosomal anomalies were present or not.