Histological appearance of early and late stages of CRMO. A) Hematoxylin and eosin (HE) stained bone biopsy in the early phase of CRMO. Neutrophils and monocytes (arrows) are the predominant cell types. B) HE stained bone biopsy showing chronic inflammation in CRMO with monocytes, lymphocytes and plasma cell infiltration. C) HE stained biopsy of the late chronic fibrosing stage in CRMO.