Epithelioid hemangioendothelioma (EHE) is a rare tumor originating from the vascular endothelium; it has an intermediate malignant potential. EHEs affect all age groups and mostly originate from the soft tissues of the extremities, lungs, and liver. Spinal EHEs, especially those occurring in the bone marrow region, are extremely rare. We report a case of EHE with massive involvement of the liver, vertebrae, and cranial bones that caused severe myelofibrosis (MF) in a 67-yr-old-male patient. Hyaluronan deposits were diffusely observed in the tumor tissue biopsies obtained from both the liver and bone marrow. Furthermore, the serum hyaluronan level increased markedly along with rapid progression of the disease. To the best of our knowledge, this is the first report of MF occurring in an EHE; hyaluronan may have played an important role in the pathogenesis of fibrosis in this case.