Hemangioma of Bone
Intraosseous hemangioma is a benign tumor of blood vessels found in the bone marrow. It often affects the vertebral column and skull and can be either solitary or multifocal. The lesion is usually asymptomatic and found incidentally via imaging studies. However, intraosseous hemangiomas can cause compressive neuropathy if there is epidural extension, fracture, or hemorrhage.
Epidemiology
Hemangioma of bone is a relatively common tumor and is often noted incidentally on spinal imaging. The lesion is not inherited but rather develops spontaneously.
Clinical Features
Most cases of hemangioma of bone are asymptomatic. However, lesions within a vertebral body can rarely extend into the epidural space and cause neurologic dysfunction. Additionally, large lesions can present with pathologic fracture or hemorrhage. Skeletal hemangiomatosis is a systemic form of the disease in which multiple hemangiomas or lymphangiomas develop within the skeleton. Patients with this condition tend to be more symptomatic due to the burden of these tumors, especially when the tumors are seen in combination with visceral hemangiomas.
Rare vascular tumors such as epithelioid hemangioma, epithelioid hemangioendothelioma, and angiosarcoma can resemble hemangioma of bone but will display more locally aggressive or frankly malignant behavior. Hemangioma of bone follows an indolent course and does not carry the risk of malignant transformation.
Radiologic Features
Hemangioma of bone appears as a lytic lesion in the marrow space, characterized by cortical thinning and prominent, hypertrophied trabeculae. However, in the flat bones, it can cause cortical expansion. When the lesion is located within a vertebral body, the horizontal trabeculae are preferentially eroded while the vertical trabeculae which support the vertebral endplates become accentuated, leading to “jailhouse vertebrae” or the “corduroy sign” on radiographs (Figure 1). These prominent vertical trabeculae appear as polka-dot calcifications on axial computed tomography (CT) scans (Figure 2).
Because blood vessels are usualy found with a thin layer of fat, the tumors can have variable fat content and thus variable signal intensity on magnetic resonance imaging (MRI). On T1 sequences, the signal is usually intermediate given the presence of some fatty component. On fluid-sensitive sequences such as short tau inversion recovery (STIR) and fat-supressed T2, the signal is often hyperintense and enhances after contrast due to the flow of blood within the tumor (Figure 3). Hemangioma of bone can be challenging to distinguish from metastatic disease on MRI, but its striated appearance on x-ray and CT can support its diagnosis. Usually, the imaging characteristics are clear and obviate the need for a biopsy which can cause significant bleeding and further local complicatios.
Pathology
Grossly, intraosseous hemangioma contains cystic, dark red, blood-filled cavities (Figure 4). Microscopically, the thin walls of the blood vessels are lined with flat endothelial cells that stain positively for vascular markers CD31 and CD34. Abundant red blood cells can also be seen.
Differential Diagnosis
Although the radiographic appearance of hemangioma can mimic that of other lytic bone tumors, CT and MRI scans can help with the definitive diagnosis of a vascular tumor. CT scans can highlight trabeculae and MRI can detect microscopic fat, features that distinguish the lesion from other potential diagnoses.
Disease Course: Treatment and Prognosis
Hemangioma of bone is usually asymptomatic and found incidentally. In such cases, no treatment of the lesion is required. However, hemangioma within a vertebral body can rarely attain a large size and cause neural compression due to epidural extension. Likewise, hemangiomas in the appendicular skeleton can cause pathologic fracture, bone pain, or intraosseous hemorrhage. Pathologic fracture is treated with immobilization or surgical intervention, just as it would be treated in the absence of the hemangioma.
Symptomatic intraosseous hemangioma is treated in a variety of ways. Minimally invasive percutaneous techniques such as intralesional ethanol injection or trans-arterial particulate embolization can be used to ablate the lesion and improve pain or neurologic deficit. Surgical decompression with tumor excision is performed in those rare instances when vertebral hemangiomas cause cord compression or are refractory to percutaneous treatment. If vertebrectomy is indicated, it should be performed after preoperative embolization which has been shown to significantly decrease the risk of catastrophic hemorrhage. Vertebroplasty can also be considered for painful lesions without neurologic symptoms.
Key Test Topics
The tissue tests positive for vascular molecular markers CD31 and CD34.
Radiologic identification of a large vertebral body hemangioma demonstrates the appearance of a “jail house” vertebrae.