Unusual Configurations of Endoplasmic Reticulum in Cells of Acute Promyelocytic Leukemia

Abstract
An ultrastructural study of leukemia cells from 8 patients with acute promyelocytic leukemia revealed several features that have not previously been emphasized: prominent dilated rough endoplasmic reticulum and two unusual configurations of endoplasmic reticulum (ER). The two membrane structures, multilaminar ER and complex stellate arrangements of ER, appeared to be morphogenetically related. The multilaminar ER was observed in every mitotic cell and less frequently in interphase cells. The stellate ER complex was observed only in interphase cells. Ultrastructural evidence is presented to support the possible evolution of the stellate ER complex from the multilaminar ER.