Histopathological finding in leukostasis. Specimen from the leptomeninges of an AML patient postmortem stained with hematoxylin and eosin (×200). (A) Large numbers of immature WBCs in a leptomeningeal capillary artery presumably leading to reduced blood flow and thrombus formation with strands of fibrin, red blood cells (RBCs), and WBCs. (B) Numerous myeloid blasts and some RBCs are present in the extravascular space, infiltrating the leptomeningeal tissue.