[Vertebral hemangioma. Definition, limitations, anatomopathologic aspects].

Vertebral hemangiomas are benign, malformative vascular tumours composed of newly formed blood vessels with normal (capillary, venous, or veno-capillary) structure and without arterio-venous shunt; they involve firstly the vertebra and may secondary extend to the epidural space. These features allow to separate vertebral hemangiomas from bone lymphangiomas, from true neoplastic vascular tumours such as hemangioendotheliomas, hemangiopericytomas, angiosarcomas, from hemangioblastomas and from arteriovenous malformations with shunt. The latter are usually associated with other vascular malformation of the skin and spinal cord in the same metameric segment(s) (metameric angiomatosis or Cobb syndrome). There are two microscopic types of vertebral hemangiomas which frequently coexist. Cavernous angiomas are composed of large dilated blood vessels closely clustered together, so that they are not separated by normal bone tissue. Capillary angiomas are formed of thin-walled capillary vessels of various sizes separated by normal bone tissue. The vascular malformation is not separated from the bone tissue by a capsule; the surrounding osseous lamellae usually show secondary osteolysis and osteocondensation, and the bone marrow undergo fibrous and/or adipose involution.