“Should I be concerned about a mole on my skin?”

—Dale R., University of British Columbia, Vancouver

This is a good question that everyone can benefit from—even in the winter. It’s a good idea to use sunblock when skiing this winter and whenever you’re out and about next summer. Though sunblock is not a guarantee that you won’t get skin cancer, it decreases the chances dramatically. So get some and smear it all over!

What is skin cancer?

As with any cancer, skin cancer occurs when normal cells change into abnormal cells. Normal cells replicate in an orderly, predictable fashion and do their assigned job wherever they are. Cancer cells are rapidly growing, disorderly, and aggressive. They overtake the environment where they’re developing, destroying everything in their way. They may spread far and wide in the body, doing more damage where they don’t belong. These new areas of growth are called metastases.

Skin cancers are classified as melanoma and non-melanoma.

  • Melanoma is relatively rare but very aggressive. These moles are usually brown or black in appearance.
  • Non-melanoma skin cancer has many types. Two of the most common—basal cell carcinoma and squamous cell carcinoma—are less aggressive than melanoma and grow more slowly. If not treated, however, they can also cause major damage.

What are the signs of a melanoma skin cancer?

If your mole has any of these features, get it checked out:

  • Asymmetrical in shape
  • Irregular, ragged, imprecise border
  • A variation in colour within the same lesion
  • Larger than 6 mm in diameter
  • Changes in colour, shape, or size, or symptoms such as itching, tenderness, or bleeding

The “ugly duckling sign:” Moles are usually round, uniform in color and kind of boring in appearance. If a mole stands out and says “Look at me,” it’s a good idea to get it checked out.

What are the signs of a non-melanoma skin cancer?

Non-melanoma skin cancer tends to be a little more dramatic. Worrisome signs include:

  • Pink or red
  • Swollen, peeling, or bleeding, like an open sore
  • Thick and crusty