The preleukemic syndrome. II. Cytogenetic findings.

Out of 151 patients with preleukemic syndrome, bone marrow chromosome studies were carried out in 88 during the preleukemic phase and in 10 after blastic transformation. Out of 54 cases studied without banding techniques, 13 (24%) were abnormal, while 17 (50%) out of 34 banded cases showed abnormalities. This highly significant increase in yield of aberrations was not restricted to structural abnormalities. During the preleukemic phase of the disease, only 5 of the abnormal patients had no normal metaphases in their bone marrow. Four types of chromosome aberrations were observed more than once: -Y, +8, del 5q and del F or del 20q. They are all frequently observed in myeloproliferative disorders. After blastic transformation, 15 out of 19 patients were abnormal and the abnormalities were more complex. It seems, therefore, that a qualitative and quantitative difference exists between this group of patients and the published series of patients with ANLL. Small abnormal cell lines with the same chromosome abnormalities as in the bone marrow were observed in PHA-stimulated blood cultures of 9 patients. Unstimulated cultures of the same blood sample did not show any mitosis. It is suggested that small subpopulations of lymphocytes arose from the same pluripotent stem cell as the leukemic myelogenous cells, although there may be other explanations.