One general rule of thumb is using the ABCD's.

A stands for asymmetry; that is, if the mole cannot be folded back upon itself; it is not symmetric.

B stands for border irregularity where the edge of the mole, the border, is irregular and not smooth and curvilinear.

C stands for color variation. If you look at the mole and it has several colors, such as dark brown, tan, black, and pink, this too is a warning sign.

D stands for diameter bigger than 6 mm, which is essentially the same diameter as a pencil eraser.

Some people even include E for elevation, moles that are sticking up.

All of these are just general indications that a mole should be evaluated by a dermatologist. They are by no means a definite diagnosis of skin cancer, just a good rule of thumb to encourage you to get the moles checked out.

Once you see a dermatologist, if the dermatologist thinks the mole looks suspicious, a biopsy may be performed. A small part of the mole or the mole in total is taken out and sent in for evaluation, often to a board certified dermatopathologist. Moles are classified as benign, premalignant, or malignant. Generally speaking, with moles that are benign, the patient can be reassured. Moles that are either precancerous or malignant need to be removed with the appropriate follow-up measures, as determined by a board certified dermatologist.

I tell my patients that if you notice a mole changing in any way, size, color, shape or if a spot bleeds without provocation and does not heal in three weeks, these should be evaluated promptly. The bottom line is this: See spot, see spot change, see a dermatologist.