Because the sun causes skin cancer, protection is vital at sea. Of the three types of skin cancers, the most dangerous and lethal is melanoma. The signs of melanoma are subtle and early detection is essential. If completely removed surgically the cure will be 100 percent effective, but if any spreads, it is 100 percent fatal. A stands for asymmetry, or an irregular mole which, when viewed with a magnifying glass and a bright light, has many bays and peninsulas.
B is for border.
If the mole s color has leaked out around the border, and the border is ragged or asymmetrical, this indicates increased risk of malignancy. C is for color. Two or more colors in a mole indicate likelihood of malignancy. If, when using a magnifying glass and bright light, one sees reds, whites and blues in the mole, this is an almost certain diagnosis for melanoma. D stands for diameter.