Hemangioma

Hemangiomas are benign lesions characterized by vascular spaces lined with endothelial cells. Approximately 50% of osseous hemangiomas are found in the vertebral bodies (thoracic especially)i and 20% in the calvarium. The remaining lesions are found in the tibia, femur and humerus. Hemangiomas are common lesions with approximately 10% of autopsy cases having vertebral hemangiomas in one study. The peak incidence is in the fifth decade. Hemangiomas are usually asymptomatic lesions discovered on x-ray or autopsy. Vertebral hemangiomas can cause neurological symptoms if they extend into the epidural space.

The radiological appearance can be quite striking and depends on the location of the lesion. Vertebral lesions have thickened vertebral trabeculae secondary to erosion of the horizontal trabeculae which gives a "corduroy" appearance on plain film. On CT scan, vertebral body lesions have a "polka dot" pattern as the vessels are seen in cross section. Calvaria lesions are lytic and resemble radiating wheel spokes. Hemangiomas in the metaphysis or epiphysis of long bones are lytic lesions that give a spiculated pattern known as "Irish lace". T1 weighted MRI scans vary from low to high intensity depending on the amount of adipose tissue present. T2 weighted MRI scans demonstrate lesions with high intensity due to the vascularity.

On gross examination, hemangiomas are cystic, dark red cavities. The lesion is well demarcated and has trabecular thickening.

Under the microscope, there are four types of hemangiomas: capillary, cavernous, arteriovenous and venous. Capillary and cavernous lesions are the most common in bone. Capillary hemangiomas contain capillary size vessels lined by flattened endothelial cells. Cavernous hemangiomas are often found in the calvaria and contain large dilated vessels with flattened endothelium. Arteriovenous hemangiomas are remnants of fetal capillary beds and venous hemangiomas contain small thick-walled venous vessels. Non-vascular components of hemangiomas include fat, smooth muscle, fibrous tissue, bone, hemosiderin and thrombus.

Treatment of hemangioma is unnecessary unless the lesion is symptomatic. Lesions in the calvarium should be resected with a thin margin of normal bone. Vertebral lesions respond to radiation or can be treated with surgical excision preceded by en embolization. Lesions in long bones should be excised and packed with bone graft if appropriate.

References
Conway, WF and CW Hayes, Miscellaneous Lesions of Bone, Radiologic Clinics of North America, 31(2):339-357, March, 1993.

Murphey, MD et al., Musculoskeletal Angiomatous Lesions: Radiologic-Pathologic Correlation, Radiographics, 15(4):892-917, July, 1995.

Bullough, Peter. Orthopedic Patholovv (third edition), Times Mirror International Publishers Limited, London, 1997.

Huvos, Andrew, Bone Tumors:Diagnosis. Treatment and Prognosis, W.B. Saunders, Co., 1991.

Adapted, with permission from bonetumor.com By Henry DeGroot III, M.D.