Pattern of nucleolar organizer regions in human leukemic cells.

The pattern of nucleolar organizer regions in bone marrow smears of 40 patients with acute myeloid leukemia (AML), 27 with acute lymphoid leukemia (ALL) and 15 control cases were studied. All normal blasts as well as leukemic blasts revealed at least one cluster of AgNORs. In AML the mean number of clusters (2.87 +/- 0.48) and dots (0.23 +/- 0.17) per cell was significantly lower than in normal myeloblasts (3.27 +/- 0.14 resp. 0.34 +/- 0.12). In ALL the number of clusters (2.82 +/- 0.62) was not significantly different from that of AML blasts. While in all control cases the distribution of the number of clusters per cell within a case could be approximated by a modified Poisson equation, this did not hold for 9 ALL and in 13 AML patients. The histogram of those cases showed a lower dispersion. In ALL, but not in AML, the number of clusters per cell correlated with the peripheral leukocyte count. The present results strengthen the concept that clusters and dots should be regarded as separate entities and suggest that their pattern is related to duration of cell cycle as it has been shown in other tissues.