There’s something you have all over your body that you’re probably not as familiar with as you should be.

It’s your skin — your body’s largest organ.

Melanoma Monday, which this year falls on May 4, is an annual day aimed at spreading awareness about skin cancer that was launched in 1995 by the American Academy of Dermatology.

Melanoma is one of the most common cancers in young people under age 30.

It’s nearly 100% curable if caught in its early stages, but a recent survey by MedStar Health finds nearly half of U.S. adults (47%) have never had their skin checked for cancer by a doctor.

“It’s a really good idea for all adults to get a baseline skin screening at some point to assess risk,” Dr. Allison Larson, physician executive director of dermatology for MedStar Health, told WTOP.

The study also found 58% of adults don’t know that melanoma is the deadliest form of skin cancer, and 83% are unaware that melanoma can become life threatening in just six weeks.

“So if you have a spot on your skin, a dark spot, a mole that is irregular, is changing, it really needs to be checked,” Larson said. “It’s not something that can wait six months or a year.”

To remember the five things to look for when monitoring your skin for cancer, think of A, B, C, D, E.

A is for asymmetry. A mole with a shape that’s different on one side compared with the other could be cancer.

B is for borders.

“Is it smooth and even, or is it scalloped and notched? Scalloped and notched would be more worrisome,” Larson said.

C is for color. More than one shade of color or a mix of different colors could be a sign of trouble.

D is for diameter. Anything bigger than a pencil eraser, or a spot or mole that’s growing larger should be checked out.

E is for evolving. Changes of any kind over time could be a warning sign.

The importance of wearing sunscreen to prevent skin cancer is well known, but Larson said many people seem to miss a key point.

“One of the most common pitfalls that I see in my patients is this idea is that if I put on a coating of sunscreen in the morning, I’m good for the whole day. The answer is, not even close. We really need to reapply every two hours, and sometimes even more often if you’re doing water sports, or sweating, or in some sort of environment where you’ll be rubbing off your sunscreen.”