Erythroblastic islands and extra-medullary erythropoiesis in chronic myeloid leukaemia.

Aspirates from bone marrow, spleen and liver were morphologically analysed in 15 untreated patients wich chronic myeloid leukaemia. Megaloblastic changes of the erythroblasts were found to be more common in the spleen and liver than in the bone marrow. A significant increase of 'erythroblastic islands', i.e. erythroblasts in contact with reticulum cells, were recorded in the leukaemia patients compared to 15 healthy controls. It is suggested that the presence of such formations may indicate an increased death rate of defective erythroblasts followed by phagocytosis into reticuloendothelial cells.