I often hear that someone has a cavernous hemangioma in their brain. So is a cavernous hemangioma a real tumor? Does it grow like gliomas and meningiomas? A cavernous hemangioma is actually a malformation of a blood vessel. As you can see in surgery, cavernous hemangiomas contain malformed veins that have immature walls and bleed easily. These venous malformations are congenital. So, why are venous malformations called tumors? Because, after bleeding from these malformed veins, the blood clots fibrose and mixed with the malformed veins to form bulbous tumors, so that whether seen on film or in surgery, they all appear as tumor-like masses and have a certain elastic texture, which is how cavernous hemangiomas got their name. Despite being called a tumor, it is essentially a malformed mass of veins. Although cavernous hemangiomas are not really tumors, they do grow. But the nature of this growth is quite different from that of a glioma, which increases in size due to tumor cell division. In contrast, cavernous hemangioma does not contain tumor cells. It grows due to repeated bleeding from the venous malformation, and each time it bleeds there is a blood clot that is not completely absorbed to form new fibrosis, which is deposited repeatedly like sediment, resulting in an increasingly larger mass encircling the malformed venous mass. Therefore, cavernous hemangiomas can “grow” as big as real tumors. Once you know about cavernous hemangiomas, you can see that they are not scary. Intracranial cavernous hemangiomas are generally well treated and are less likely to recur after surgical removal.