include lymphedema, radiation therapy, neurofibromatosis, Maffucci syndrome, Klippel-Trenaunay syndrome and chemicals such as arsenic, thorotrast and vinyl chloride. A 2020 study analyzing the genome of cutaneous angiosarcomas suggests that ultraviolet radiation may be a causative agent of angiosarcomas. Immunosuppression may play a role in the pathogenesis of angiosarcoma. There have been reports of angiosarcoma in immunosuppressed individuals following kidney transplantation. The association between lymphedema and angiosarcoma may be due to localized immunodeficiency, however this hypothesis has not been confirmed. Some studies suggest a link between AIDS and angiosarcoma though this may be due to misdiagnosed Kaposi's sarcoma. Diagnosis The diagnosis of angiosarcoma can be difficult due to its asymptomatic nature or non-specific symptoms. Initial diagnosis is typically done by MRI, CT or ultrasound scan, however it is typically difficult to discern if a mass is an angiosarcoma or other type of tumor such as a melanoma or carcinoma. This means that while the initial diagnosis is typically done via imaging, conclusive diagnosis has to be performed via biopsy and subsequent histological and immunohistochemical analysis. The marker CD31 is often considered the gold standard for angiosarcoma diagnosis due to its high sensitivity and specificity. Other markers typically used include von Willebrand factor, CD34, and vascular endothelial growth factor. The absence of markers present in melanomas such as S100 and HMB-45 can help in differentiating angiosarcomas from melanomas. Epidemiology Angiosarcomas are rare with one in a million people being diagnosed with it each year in the US. Older adults are more commonly affected and there is no gender bias, except in angiosarcoma of the liver where males are affected in a ratio of 3-4:1 and cutaneous angiosarcoma where males are again affected more commonly, particularly elderly white men. Animals In dogs, hemangiosarcoma is relatively common with the golden retriever, boxer and labrador retriever at higher risk of the disease than other breeds. It occurs primarily in the spleen, liver, heart, skin and subcutaneous layer of the skin. It is rapidly fatal and metastatic and can present with anything from nonspecific signs to imminent death from tumor rupture. See also Glomangiosarcoma List of cutaneous conditions References Dermal and subcutaneous growths Rare cancers Sarcoma Vascular neoplasia