Fibrous long spacing-like fibers in the bone marrow of myloproliferative disorder

Abstract

Bone marrow obtained at autopsy from four cases of primary myelofibrosis and four cases of chronic myelogenous leukemia, was studied electron microscopically. In all the cases of primary myelofibrosis, the excess of collagen fibers in the bone marrow showed mostly about 2,000 A diameter and 1,000 A periodicity, i.e. fibrous long spacing (FLS)-like fibers. These FLS-like fibers were also seen in secondary myelofibrosis in three of the four cases of chronic myelogenous leukemia. These fibers were abundant around fibroblasts and small blood vessels. An apparent continuity between the dark bands of FLS-like fibers and the basement membrane material around small blood vessels was also revealed. Moreover, it was observed that these dark bands of FLS-like fibers contained acid mucopolysaccharides.