Adults should practice skin self-exam once a month, and suspicious lesions should be evaluated promptly by a physician. Basal and squamous cell skin cancers often take the form of a pale, waxlike, pearly nodule, or a red, scaly, sharply outlined patch. A sudden or progressive change in a mole's appearance should be checked by a physician. Melanomas often start as small, mole-like growths that increase in size and change color. One half of the mole does not match the other half.
B is for border irregularity.
The edges are ragged, notched, or blurred. C is for color. The pigmentation is not uniform or intensely black. D is for diameter greater than 6 millimeters. Any sudden or progressive increase in size should be of particular concern.