A cavernous hemangioma is a cluster of abnormal, enlarged blood vessels that form a slow-growing, non-cancerous mass. These vessels are thin-walled, filled with blood, and lined by a single layer of cells, giving the mass a sponge-like or berry-like structure. Cavernous hemangiomas can develop in the liver, brain, skin, spleen, and other organs, and most are discovered by accident during imaging for an unrelated problem.
What Happens Inside the Lesion
Under a microscope, a cavernous hemangioma looks like a tangle of oversized blood-filled cavities. These cavities are much larger than normal capillaries and are separated by thin walls made of connective tissue. Unlike healthy blood vessels, the walls lack the muscle and elastic fibers that help regulate blood flow. Because of this, blood moves sluggishly through the spaces, sometimes clotting within them. The slow blood flow and fragile walls are the root of most complications these lesions can cause.
Liver: The Most Common Location
The liver is where cavernous hemangiomas show up most often. They account for roughly 73% of all benign liver tumors, appearing in anywhere from 0.4% to 7.3% of the population depending on the study. Most are small, cause no symptoms, and are found incidentally on an ultrasound or CT scan done for something else entirely. They are the second most common tumor found in the liver after metastatic cancer, but unlike metastases, they pose no risk of spreading.
Most liver hemangiomas never need treatment. Even large ones can be safely monitored if they aren’t causing problems. Surgery is typically considered only when a hemangioma grows beyond about 5 cm and causes progressive abdominal pain. In surgical series, the average size of lesions that were removed was around 10 cm, compared to about 5 cm for those left alone. Observation alone is appropriate for people with minimal or no symptoms, regardless of size.
The Role of Hormones
Liver hemangiomas are more common in women, and female sex hormones appear to play a role in their growth. Several studies have documented size increases during pregnancy and in women taking hormone therapy, though this link isn’t found in every study. In one analysis, about 23% of women on hormone therapy saw their hemangioma grow, compared to roughly 10% of women who were not. Hormone therapy increased the risk of enlargement by about threefold. That said, significant growth still occurs in only a minority of patients, so the presence of a hemangioma doesn’t automatically rule out hormone-based treatments.
Brain: Cavernous Malformations
When a cavernous hemangioma forms in the brain, it’s more commonly called a cerebral cavernous malformation, or cavernoma. These are clusters of abnormal capillaries in brain tissue that can leak small amounts of blood into the surrounding area. They look distinct on MRI, often described as having a “popcorn” appearance because of the mix of blood in different stages of breakdown, surrounded by a dark ring of iron deposits left by old bleeding.
About half of people with symptomatic brain cavernomas experience seizures as the first sign. Roughly 25% present with a noticeable bleed, and another 25% develop neurological symptoms like weakness, numbness, or vision changes without clear evidence of a new hemorrhage. Many cavernomas, however, are completely silent and discovered only when imaging is done for headaches, injuries, or other reasons.
Bleeding Risk in the Brain
The annual risk of bleeding depends heavily on whether the cavernoma has bled before. For a lesion discovered incidentally with no bleeding history, the yearly hemorrhage risk is low, around 0.33%. For lesions that have never bled but are causing symptoms, the rate is estimated at 0.7% to 1.1% per year. Once a cavernoma has bled, though, the risk jumps to about 4.5% per year. Over five years from diagnosis, the cumulative risk of hemorrhage across all patients is estimated at roughly 16%.
Most bleeds from brain cavernomas are small. Because the blood vessels are low-pressure, hemorrhages tend to be slow oozes rather than the sudden, catastrophic bleeds associated with other vascular problems. Still, even small bleeds in sensitive areas like the brainstem can cause significant neurological symptoms.
Treatment for Brain Cavernomas
Many brain cavernomas are managed with observation and periodic MRI scans, especially when they’re small, in a non-critical location, or haven’t bled. When treatment is needed, the two main options are microsurgery (physically removing the lesion) and stereotactic radiosurgery (focused radiation). A meta-analysis comparing the two approaches for brainstem cavernomas found no clear superiority of one over the other in terms of mortality, later rebleeding, or new neurological deficits. Microsurgery eliminates the bleeding risk immediately but requires complete removal and carries its own surgical risks. Radiosurgery is less invasive but doesn’t remove the lesion, and its protective effect develops gradually over months to years.
Skin: Deep vs. Superficial Lesions
On the skin, hemangiomas are classified by depth. Superficial ones sit in the upper layers of skin and appear as raised, lobulated, bright red growths, sometimes called “strawberry” hemangiomas. Deep hemangiomas, which include the cavernous type, arise from lower skin layers and the tissue beneath. They typically appear as a bluish, soft nodule or swelling under the skin rather than a red surface mark. Some hemangiomas are mixed, with both superficial and deep components. Skin hemangiomas are most common in infants and often shrink on their own over the first several years of life.
Causes and Genetics
Most cavernous hemangiomas occur sporadically, meaning there’s no family history and no clear trigger. For brain cavernomas specifically, however, a hereditary form exists. Familial cases follow an autosomal dominant inheritance pattern, meaning a child has a 50% chance of inheriting the condition if one parent carries the gene. Three genes have been identified: mutations in these genes account for about 95% of familial cases. Among patients with confirmed mutations, roughly 65% have changes in the first gene, 19% in the second, and 16% in the third. Even 5% to 15% of familial cases remain genetically unexplained, suggesting other genes may be involved.
People with the familial form tend to develop multiple cavernomas throughout the brain, while sporadic cases usually involve a single lesion. Genetic testing can be useful when someone has multiple brain cavernomas or a family history of the condition, as it can help guide screening for relatives who may be affected but not yet symptomatic.
A Rare Complication Worth Knowing
In uncommon cases, large cavernous hemangiomas can trigger a condition called Kasabach-Merritt syndrome. This happens when blood platelets get trapped inside the abnormal blood vessels of the hemangioma, leading to dangerously low platelet counts and problems with blood clotting. The abnormally proliferating cells lining the hemangioma essentially snare platelets as blood passes through, which then triggers a chain reaction that consumes clotting factors throughout the body. This syndrome is rare, more often reported with skin hemangiomas than internal ones, but it can also occur with splenic or liver lesions. It requires prompt treatment, which may include removing the hemangioma itself.