By Dr. Brian McDonough, Medical Editor

PHILADELPHIA (CBS) - Malignant melanoma is the most serious form of skin cancer. When we talk about the major problems associated with skin cancer, including fatalities, it is malignant melanoma that is mostly involved.

The best chance you have to defeat malignant melanoma is to detect it early. I have an easy way to measure this. Just remember a-b-c-d when you see a suspicious mole.

A is asymmetrical. We worry about moles that are not round.

We also worry about irregular borders. That is the b.

C stands for color. You should be concerned about moles that have several different colors or change in color.

Finally the diameter– that’s the d. If the mole is bigger than an eraser head it is a concern.

Remember – ABCD.