A basal cell carcinoma (BCC) usually looks like a raised, smooth, pearly bump on the sun-exposed skin of the head, neck, or shoulders.

• Small blood vessels may be visible within the tumor.

• A central depression with crusting and bleeding (ulceration) frequently develops.

• A BCC is often mistaken for a sore that does not heal.

A squamous cell carcinoma (SCC) is commonly a well-defined, red, scaling, thickened patch on sun-exposed skin.

• Like BCCs, SCCs may ulcerate and bleed.

• Left untreated, SCC may develop into a large mass.

The majority of malignant melanomas are brown to black pigmented lesions.

• Warning signs include change in size, shape, color, or elevation of a mole.

• The appearance of a new mole during adulthood, or new pain, itching, ulceration, or bleeding of an existing mole should all be checked by a health-care provider.

The following easy-to-remember guideline, “ABCD,” is useful for identifying malignant melanoma:

• Asymmetry-One side of the lesion does not look like the other.

• Border irregularity-Margins may be notched or irregular.

• Color-Melanomas are often a mixture of black, tan, brown, blue, red, or white.

• Diameter-Cancerous lesions are usually larger than 6 mm across (about the size of a pencil eraser), but any change in size may be significant.