Angiosarcoma is a rare and aggressive cancer that starts in the endothelial cells that line the walls of blood vessels or lymphatic vessels. Since they are made from vascular lining, they can appear anywhere and at any age, but older people are more commonly affected, and the skin is the most affected area, with approximately 60% of cases being cutaneous. Specifically, the scalp makes up ~50% of angiosarcoma cases, but this is still <0.1% of all head and neck tumors. Since angiosarcoma is an umbrella term for many types of tumor that vary greatly in origin and location, many symptoms may occur, from completely asymptomatic to non-specific symptoms like skin lesions, ulceration, shortness of breath and abdominal pain. Multiple-organ involvement at time of diagnosis is common and makes it difficult to ascertain origin and how to treat it. The cause of angiosarcoma is not known, though several risk factors are known, such as chronic lymphedema, radiation therapy and various chemicals such as arsenic and vinyl chloride. Ultraviolet radiation and localized immunodeficiency may play a role in pathogenesis of angiosarcoma. Angiosarcoma can be seen on MRI, CT and ultrasound scans, but it is usually difficult to discern it from other cancers, requiring confirmation of diagnosis by biopsy and immunohistochemical analysis. Treatment includes surgery, chemotherapy and radiation therapy, usually all three combined. Because these cancers arise from the cells lining the blood or lymphatic vessels, they can easily metastasize to distant sites, particularly the liver and lungs. This makes them especially lethal, and an early diagnosis is usually necessary for survival. Even with treatment, prognosis is poor, with a five-year survival rate of 30–38%. This is even worse in cardiac angiosarcoma and angiosarcoma of the liver, where prognosis may be as low as three months. Angiosarcomas make up 1–2% of soft tissue sarcomas, which in turn make up less than 1% of adult cancer. Due to this, no large studies have ever been published on the disease, with few exceeding even 100 patients; however, many case reports and small cohort studies have been published, and they cumulatively provide enough information to get a useful understanding of the disease. The rate of angiosarcoma is increasing in the US. Classification The classification of angiosarcoma is based on both its origin and the underlying risk factors that may have contributed. This is not a comprehensive list and case reports often go into further depth. Primary