Malignant melanoma, a very serious skin cancer is mostly found undetected on the legs. This Skin Cancer Leg generally remains unseen at the back of the legs especially the back of the knee and the anterior part of the upper part of the leg. Generally the moles here are asymmetrical in size with irregular borders. The color changes from black or brown to white which is the key to identify the cancerous mole. When initially these moles are detected then it has to be taken a proper medical care or else this cancer most of the time is fatal for the affected person. One can try to prevent this cancer by application of sunscreen containing SPF in large amount while exposed to the sun.