A survey of chromosome patterns in human leukemia was aimed at determining: departures from diploidy in different types of acute and chronic leukemia, influence of therapy on chromosome constitution, frequency of aneuploidy in freshly aspirated marrow compared with the same sample after short-term tissue culture. Exact chromosome counts were obtained in over 3,600 metaphases from 34 leukemic (including two mongols) and 60 nonleukemic marrows.

Human leukemias as a whole were characterized by a greater variability in chromosome structure and number (56.4 ± 1.2 per cent aneuploid) than control marrows (12.2 ± 0.8 per cent aneuploid). This was true even for leukemias with diploid modal karyotypes. Acute lymphoblastic leukemias as a group had the highest incidence of aneuploidy (77.0 ± 1.6 per cent). Chemotherapeutic treatment did not seem to enhance chromosome anomalies; on the contrary, two aneuploid leukemias in remission during therapy reverted to normal counts of 46. Marrow samples from nine leukemic patients were examined by two methods: fixation immediately after sternal aspiration (58.8 ± 2.9 per cent diploid) and after 10 hours' incubation (84.4 ± 4.4 per cent diploid). Apparently diploid cells can resume mitosis in vitro before the less adaptable aneuploids (P = <.01). The “direct squash” of freshly aspirated marrow, therefore, provides a more accurate index of the leukemic population components existing in vivo. All published chromosome data for human and mouse leukemias are summarized, and their possible etiologic implications are discussed.

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Supported in part by grants T-182 from the American Cancer Society and C-5107 from the U.S. Public Health Service.

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