A ? developmental characteristic of the ultrastructure of childhood leukaemic lymphoblasts.

Areas of chromatin demarcated from the rest of the nucleus ("separations") were found frequently in acute lymphoblastic leukaemias of childhood, in some patients in apparently all leukaemic cells, but rarely in non-lymphocytic leukaemias. In normal lymphocytes, separations were most common in fetal thymus, and less frequent in fetal lymph node and bone marrow, and child thymus, lymph node and marrow. Separations may be a developmental marker, and fetal lymphoid tissues, especially thymus, may have significance in the origin of lymphoblastic leukaemias of childhood. Nuclear loops enclosing cytoplasmic material were associated with, and may have similar significance to, separations.