Liver blood vessel tumour. Gross specimen of an haemangioma (dark patch) in a liver tissue sample. An haemangioma is an abnormal growth, also called an arteriovenous malformation, of blood vessels. A liver haemangioma is the most common primary liver tumour, often not discovered until autopsy. Most do not produce symptoms, but those that do and are large may rupture and cause severe bleeding. These cases would require surgery.