Comparative ultrastructural morphometric studies of micromyeloblastoid and lymphoblastoid paramyeloblasts.

One hundred lymphoblastoid and one hundred micromyeloblastoid paramyeloblasts, isolated from peripheral blood of untreated leukaemia patients, were studied by electron microscopic morphometry. Considerable differences are to be found between the micromyeloblastoid and lymphoblastoid paramyeloblasts as regards the size of the nucleolar "apparatus", both in the absolute average values and in the index showing the ratio of the nucleolous of the remaining nuclear surface (4.76% for myeloblastoid and 9.96% for lymphoblastoid paramyeloblasts). The central heterochromatin (scattered), which is discussed to be essential for the detection of an early prophase, was found in 3% of the myeloblastoid cells and in 14% of lymphoblastoid ones. The effect of cytostatic therapy is discussed by taking these data into consideration.