How to Spot a Cancerous Mole

Close up of mole on skin.
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If you had to guess what type of cancer only accounts for 5 percent of skin cancer cases yet leads to a large number of cancer-related deaths, what would you say? If you guessed melanoma, then you're right [source: ACS]. Melanoma can look just like a mole, but the cells inside a melanoma are cancerous and can spread throughout your body.

Knowing a little about your skin will help you understand how to spot a cancerous mole. Your skin has several layers. The epidermis, or top layer, is very thin, but it has a big job; it protects the other layers of skin. Inside the epidermis are cells called melanocytes, which make melanin, a colored chemical that protects your skin. Melanin is the part of your skin that tans when you are in the sun. Normally, melanocytes are spread throughout the epidermis. Sometimes, however, small groups of melanocytes will group together forming a mole. Although it's not known exactly why moles form, some scientists think DNA might affect this. [ACS].


Most people have moles. In fact, most Americans have between 10 and 40 of them but perhaps don't even know that they have that many [source: MedlinePlus]. Common moles are less than ¼ inch (6.35 mm) in diameter and can develop from birth to adulthood [source: Mayo Clinic]. Sometimes hormonal changes -- like during puberty or pregnancy -- can cause new moles to appear or cause existing moles to change size or color.

Melanoma is a cancer that begins in a melanocyte. It often looks like a mole but is not a mole. If it is diagnosed early, patients have a high survival rate [source: ACS]. Early diagnosis is possible, especially if you maintain a schedule of frequent self-exams and regular doctor visits. The trick is in knowing what to look for.

Read on to learn how to spot a cancerous mole and find out what type of mole increases the likelihood of developing this deadly cancer.


Cancerous Mole Signs

We all have things we do every month like checking the air pressure in the family car's tires, balancing the checkbook, giving the dog heartworm medicine. It's easy enough to add one more thing to the list --especially when it might save your life. Check your freckles and moles every 30 days -- take  note of what they look like and if any of them have changed. Change can mean a potential problem.

During your monthly mole monitoring, use the ABCDE method from the American Academy of Dermatology:


  • Asymmetrical: When you draw a line down the middle of your mole, the two sides should mirror each other.
  • Irregular border: Moles should have a definite border. Melanoma borders usually have notches or scallop shapes.
  • Changes in color: A mole might be dangerous if you notice the color isn't consistent throughout.
  • Diameter: A mole should be no larger than ¼ inch (6.35 mm) in diameter.
  • Evolving: A mole that sometimes changes in shape, color, height or texture is suspect. If you develop a new mole and it starts to itch or burn, it could be a sign that it's not healthy [source: Mayo Clinic].

Any mole that is asymmetrical, has an irregular border, changes in color, size, shape, height or texture, hurts or oozes fluids or blood should be shown to your doctor. During your annual appointment, your doctor may perform a complete skin check.

There are a few things that you should keep in mind in addition to these physical signs. You may be at high risk for developing melanoma if you have dysplastic moles. These moles are larger than ¼ inch (6.35 mm), have dark centers and irregular borders. Often they are hereditary, so other members of your family may have them as well. Even a single dysplastic mole will mean your risk of developing melanoma has doubled. If you have a family history of skin cancer or more than 50 moles, you also are at an increased risk [source: Mayo Clinic].

You've found a suspicious mole and you've made an appointment to see your doctor. What happens next? Read on to find out.


Dealing with Potentially Cancerous Moles

It might be difficult to believe that something as small and innocuous looking as a freckle or mole could be lethal, but it's possible. So, the bottom line when dealing with a mole that looks suspicious is -- see a doctor. It might simply be a funny-looking mole, but if it is cancerous, you'll be glad you sought help. Early detection is key. The cells in a melanoma can break off and spread to other parts of your body. Usually they make their way to your lymph nodes, and then to other organs like your lungs.

If the doctor thinks that your mole could be cancerous, he or she will most likely decide to remove a piece of it to send to a lab for a biopsy, or examination. If the mole is smaller than 3/8 of an inch (9.5 mm) in diameter, it will probably be removed completely [source: Mayo Clinic]. In a lab, a pathologist will use a microscope to see if it is actually cancerous. If it is cancerous, you may be referred to a specialist, who might want the mole to be completely removed, including a small section of healthy skin around the mole. At this time, the physician will also check your lymph nodes to see how big they are -- enlarged lymph nodes could be a sign that the cancer has spread. The physician might take another biopsy to rule out that the cancer has spread to the lymph nodes. Other tests, like x-rays or CT scans, can help the physician see if your organs have been affected by the cancer [source: Mayo Clinic].


If the cancer has spread beyond your skin, treatments may include chemotherapy, radiation therapy, and biological therapy to kill cancer cells in different parts of your body.

Dealing with a cancerous mole is simplest if you discover it early -- so that it can be treated before it can spread throughout your body. Regular self-exams and doctor visits could prevent a small mole from changing your life.

For more details, visit the Web sites on the next page.


Lots More Information

Related HowStuffWorks Articles

  • American Cancer Society. "How is Melanoma Diagnosed?" 5-14-09. (Accessed 9/16/09)
  • American Cancer Society. "What Is Melanoma?" 5-14-09. (Accessed 9/16/09)
  • American Cancer Society. "What Are the Key Statistics About Melanoma?" 5-14-09. (Accessed 9/16/09)
  • American Cancer Society. "How is Melanoma Staged?" 5-14-09. (Accessed 9/16/09)
  • Gibson, Lawrence E., MD. "Freckles and Moles: What's the Difference?" Mayo Clinic (Accessed 9/16/09)
  • Mayo Clinic. "Moles." 2-19-08. (Accessed 9/16/09)
  • Mayo Clinic. "Melanoma." 6-3-08. (Accessed 9/16/09)
  • MedlinePlus. "Moles." 9/23/09. (Accessed 10/6/09)