Hemangiosarcoma of the skin and tissues just beneath it has a notably different behaviour from the visceral (organ-based) forms of this cancer. Dermal hemangiosarcoma, found in the outermost layer of skin, is often caused by chronic sun exposure (ultraviolet radiation) and tends to occur on the thinly haired ventral abdomen of light-skinned dogs. This sun-induced form generally carries a better prognosis because it is caught earlier and is less likely to spread internally. Subcutaneous hemangiosarcoma, found in the fatty tissue beneath the skin, behaves more aggressively — intermediate between dermal and visceral forms. Short-haired, lightly pigmented breeds such as Whippets, Greyhounds, and Dalmatians are most at risk for the sun-induced variant.