Intraosseous hemangiomas are caused by an abnormal buildup of blood vessels inside bone. They are benign vascular lesions, not true cancers, and they account for less than 1% of all primary bone tumors. The exact trigger remains unclear in most cases, though the growths are thought to arise from a developmental error in how blood vessels form within bone tissue. Most are discovered incidentally on imaging done for unrelated reasons and never cause symptoms.
Why Blood Vessels Grow Abnormally in Bone
An intraosseous hemangioma forms when small blood vessels inside bone proliferate and cluster together in a disorganized way. Rather than following the normal vascular architecture of healthy bone marrow, these vessels expand into tangled masses that gradually replace normal bone structure. The process is slow, often taking years or decades, which is why most people don’t know they have one.
The underlying cause in the vast majority of cases is unknown. These lesions are generally considered congenital or developmental, meaning the error likely occurs early in life even if the growth isn’t detected until much later. A small number of families carry inherited mutations in a gene called ELMO2, which causes a condition involving intraosseous vascular malformations. Only a handful of families worldwide have been identified with this genetic pattern, so it explains a very small fraction of cases. For most people, no specific genetic or environmental cause can be pinpointed.
Where They Form Most Often
These lesions have a strong preference for certain bones. The spine is the most common location, accounting for 30 to 50% of all cases. The skull is next, representing about 20%. Involvement of other bones, including the ribs, long bones of the arms and legs, and the small bones of the hands and feet, is extremely rare.
The location matters because it influences both the type of hemangioma and the likelihood of symptoms. Hemangiomas in the spine tend to be the capillary type, made up of dense networks of tiny blood vessels. Those in the skull are usually the cavernous type, consisting of larger, dilated blood vessel channels separated by walls of fibrous tissue. A third category, the mixed type, has features of both.
Who Gets Them
Intraosseous hemangiomas can appear at any age, but they’re most commonly diagnosed in people in their 30s through 50s. Women are affected roughly three times as often as men. Because these lesions grow so slowly and rarely cause problems, many are only found when someone gets a CT scan or MRI for back pain, a head injury, or another unrelated issue. Autopsy studies suggest they’re far more common than clinical diagnosis rates indicate.
How They Cause Symptoms
The vast majority of intraosseous hemangiomas are completely silent. When symptoms do occur, the mechanism depends on where the lesion sits and how it interacts with surrounding structures.
In the spine, a hemangioma can become what clinicians call “aggressive,” though the term refers to local behavior, not cancer. There are at least four ways a vertebral hemangioma can press on the spinal cord or nearby nerves: the back wall of the vertebral body can bulge outward as the lesion expands, the abnormal blood vessels can extend through the bone’s outer shell into the space around the spinal cord, the weakened vertebra can fracture under normal body weight, or bleeding from the lesion can form a blood clot that compresses the cord. Any of these can cause localized back pain, radiating nerve pain, numbness, or weakness in the arms or legs.
In the skull, hemangiomas typically present as a slowly growing, painless bump. Because the skull doesn’t house a spinal cord, the concern is more about cosmetic deformity or, in rare cases, pressure on the brain if the lesion grows large enough.
How They’re Identified
CT scanning is considered the best tool for evaluating intraosseous hemangiomas. On a CT, the classic appearance is a well-defined area of bone with a distinctive internal pattern. In the spine, thickened vertical bone struts create a polka-dot appearance on cross-section. In the skull or face, the pattern can look like a honeycomb (many small chambers), a soap bubble (fewer, larger chambers), or a sunburst (bony struts radiating outward from a central point like spokes on a wheel).
MRI provides additional information about how much blood flow is present and whether the lesion contains more fat or more active blood vessels. Smaller lesions tend to be bright on all MRI sequences because they contain a lot of fatty marrow. Larger, more vascular lesions look different depending on the sequence used and light up intensely when contrast dye is injected. These imaging characteristics help distinguish hemangiomas from other bone conditions that can look similar, including Paget’s disease (which causes coarsened, expanded bone), fibrous dysplasia, and fatty bone tumors.
What Happens After Diagnosis
Most intraosseous hemangiomas require no treatment at all. If one is found incidentally and isn’t causing pain or pressing on anything important, the standard approach is simply to leave it alone. These lesions don’t transform into cancer.
For hemangiomas that cause mild to moderate pain, management typically starts with pain control and periodic monitoring. If nerve compression or spinal cord symptoms develop, the situation changes. Options for symptomatic lesions include injecting a hardening agent into the lesion to shut down its blood supply, blocking the feeding blood vessels to shrink it, targeted radiation, or a procedure that fills the weakened bone with a cement-like material to stabilize it. Surgery to directly remove the lesion and relieve pressure on the spinal cord is reserved for people with significant neurological problems like weakness or difficulty walking.
The choice between these approaches depends on the severity of symptoms, the size and location of the lesion, and how much it’s affecting surrounding structures. People with incidental findings on imaging can generally expect the lesion to remain stable and symptom-free for life.