Malignant and reactive erythroblasts in erythroleukemia (M6).

A cytogenetic and cytological study of 16 cases of erythroleukemia (M6) is reported. No chromosomal abnormalities were observed in 10 cases. Abnormalities were present in the other 6 cases, of which 4 were complex abnormalities. It was not possible to establish any correlation between the occurrence of morphologic abnormalities of the erythroid and megakaryocyte-platelet series and the presence of cytogenetic defects. Studies of mitoses by cytologic and cytogenetic methods concurrently performed in some cases suggest that two types of erythroleukemia can be distinguished: (1) cases with chromosomal abnormalities and a persistence of erythroblast mitoses in vitro (which suggests that the erythroblasts belong to the leukemic clone) and (2) cases with no chromosome abnormality and a disappearance of erythroblast mitoses after culture, suggesting that the erythroblasts are not members of the leukemic clone.