A tissue sample must be taken and a biopsy performed on a mole that changes in appearance, itches, oozes or bleeds, according to WebMD. Changes or irregularities in symmetry, size, color and the shape of border edges are key factors in differentiating a normal mole from melanoma.
A problematic mole is one that displays two sides that do not match, ragged and uneven borders, variations in color and shades, a diameter larger than a pencil eraser, and has become suddenly elevated, larger or smaller, explains WebMD. Irregular shaped moles that are 1/4 inch in diameter and of mixed color with fading borders are called atypical moles. While they are not cancerous, they can develop into cancerous lesions. Late-stage malignant melanoma is a serious and hard to treat illness; early detection and intervention is key to a successful prognosis. If a mole is determined to be cancerous, it is removed, along with a portion of the surrounding skin, and additional treatments, such as chemotherapy, radiation and immunotherapy, may be required.
Basal-cell carcinoma and squamous-cell carcinoma are two common forms of non-melanoma skin cancer with successful cure rates if detected early and treated, states WebMD. Having skin cancer once predisposes individuals for a recurrence; checkups are advised at least annually.