We had Dr. Amy Derick, a clinical i

We had Dr. Amy Derick, a clinical instructor of dermatology at Northwestern University, walk us through these common guidelines.

Know Your ABCDEs
A stands for asymmetry. If one half of a mole looks different from another, that's a sign that the mole could be cancerous.
B stands for border irregularity. Irregular, poorly defined, or blurred borders can be a sign of melanoma.
C is for color. Particularly dark or multicolored moles may be risky.
D stands for diameter. Moles larger than pencil erasers are noteworthy, though melanoma can be smaller too.
E is for evolution, or change. A mole that's changing in size, shape, or color is definitely one that should be checked out.
If anything seems amiss or if you are unsure whether a mole is risky or not, you should see a board-certified dermatologist. A dermatologist will be able to spot reasons for concern much more easily than you, so do not attempt to diagnose yourself — or assume you're in the clear.

There are some apps that say that they can evaluate a mole for you, but Derick says she wouldn't trust them with your life. Even if an app can tell you that a mole might be risky, it can't confirm that by taking a biopsy like a doctor can.

Still, there is some action you can take on your own. The American Academy of Dermatology recommends that you conduct a monthly self-examination, taking note of the moles you already have on your body and carefully examining any new ones that show up. A partner can help check spots that are harder for you to see.

This infographic from the AAD shows how to check your skin for a potential melanoma.
Spotting skin cancer early is essential because that means the cancer can be removed before it spreads. Most skin cancers are caused by exposure to ultraviolet light from the sun. People with lighter skin that burns easily are more susceptible to various skin cancers, though anyone's skin can be damaged by sunlight.

The two most common types of skin cancer, basal cell carcinoma and squamous cell carcinoma, both usually occur on parts of the skin that are frequently exposed to the sun — the head, neck, face, hands, arms and legs — though they can develop elsewhere. They don't spread as quickly as melanoma but can still spread to other parts of the body. Basal cell carcinoma grows wide and deep, which can be disfiguring if it's not removed at an early stage.

Many screenings focus on melanoma since it can spread much more quickly. If removed early the cure rate is almost 100%, but as the cancer spreads to nearby skin, lymph nodes, or internal organs, 5-year survival rates drop rapidly. The American Academy of Dermatology says that if people are familiar with warning signs and regularly examine their skin, along with visiting their doctors, the number of melanoma deaths could be much lower.