It can be unsettling when you find an irregular mark on your skin, from lumps and bumps to moles and more. But most of the time, these marks won't hurt you. They're often just a normal, harmless part of the body.

Still, if you see new or abnormal marks appear, you shouldn't ignore them. Sometimes, they can signal more serious conditions, such as skin cancer, a disease that can get worse over time and potentially be life-threatening. If something is wrong, acting early could help save your life.

That's why it's important to know how to identify skin cancer and who to call if you're worried you may have it.

Types of Skin Cancer

Skin cancer is the most common type of cancer there is: Up to 20 percent of Americans will get it by age 70, says the Skin Cancer Foundation. Fortunately, nearly all of them will develop the two least serious, most treatable types:

  • Basal cell carcinomas can involve scar-like marks, patches, bumps, growths, or sores on areas that typically see a lot of sun, such as the head, back, or shoulders. Approximately 4 million new cases of basal cell carcinoma get diagnosed yearly, but they rarely spread to other parts of the body.
  • Squamous cell carcinomas can involve patches, growths, lumps, or sores that tend to appear on smaller areas prone to sun damage, such as the ears or hands. Doctors diagnose approximately 1 million new cases of squamous cell carcinoma yearly, but even with a low death rate, they still can spread fast without treatment.

The less common but more serious skin cancer types include the following:

  • Melanoma, which can look like strange moles on the body, even in areas that don't see sunlight. Roughly 200,000 people get diagnosed with a new case of melanoma each year—and although it's highly dangerous, it's also treatable when caught early.
  • Merkel cell carcinoma, which can be a firm, painless bump—most often on the neck, head, or eyelids. Incredibly rare but very dangerous, Merkel cell carcinoma gets newly diagnosed in approximately 2,500 people each year.

How to Identify Skin Cancer

Because skin cancer varies by type, it can also vary by presentation, meaning how it looks on the skin. Painful or painless moles, bumps, growths, discolorations, and other markings could all indicate skin cancer lesions, but they can also signal normal, less harmful things, such as aging, freckles, or bug bites.

Dermatologists offer this advice: Check your skin once a month in a mirror, looking extra close at typically overlooked areas, such as your underarms, buttocks, and between your toes. Note any marks you see, following this guide from the American Academy of Dermatology.

If you see the following, book a visit with a Dermatologist:

  • New spots on the skin that you haven't noticed before
  • Spots that aren't the same as other marks on your body
  • Sores that don't heal
  • Red, discolored, or swollen skin near a mole
  • Existing spots that have changed since the last time you checked your skin
  • Marks that itch or bleed—or persistent or recurring pain in the skin

Know the ABCDEs of Melanoma

Outside of that general guidance, doctors have also listed specific tips to identify melanoma in the hopes of catching it early. According to the American Cancer Society, only 25 percent of people diagnosed with late-stage melanoma will live past five years. If doctors treat it in the earliest stages, those odds go up to a staggering 99 percent.

For your best chances of detecting this dangerous growth as early as possible, check for the ABCDEs of melanoma. Watch for moles or spots that have these warning signs when you do self-exams:

  • Asymmetry: If you drew a line down the mark, it wouldn't look the same on both sides.
  • Border: The mark lacks a regular, well-defined border against the surrounding skin.
  • Color: The mark isn't the same color throughout—you may see some browns, blacks, whites, or other colors.
  • Diameter: The mark is about the size of a pencil eraser, around 6 mm (but melanoma can also be smaller than that).
  • Evolving: The mark has changed over time in shape, size, or color—or otherwise doesn't match other marks on your body.

If you notice any of these signs, call a Dermatologist right away and schedule an appointment.

Be Careful with Self-Diagnosis

Though you should monitor your skin with regular self-exams, doctors are your best resource if you see something that worries you. Trying to diagnose yourself by what you read or watch online could be a mistake, as missing a key detail might ultimately delay treatment, putting your health at risk.

You shouldn't wait until you've spotted an irregular mark on your skin to find a doctor. In general, it's best to book an annual visit with a Dermatologist at least once a year for a skin cancer screening. That way, you'll already have someone familiar to call if you need something checked. For tips on picking a Dermatologist, you can refer to the guide published by the American Academy of Dermatology.

Abnormal marks of any kind can be worrisome, so having an expert on hand to rule out cancer can give you peace of mind. And if you do get diagnosed with skin cancer, knowing is half the battle. The sooner you have the information you need, the sooner you can make a plan and take action to resume a cancer-free life.