The skin is the largest organ in the body and skin cells are constantly growing to replace skin that is shed off or damaged. Skin cancers all start with a single defective cell. The cell becomes damaged, usually by ultraviolet radiation from sun exposure. This radiation changes the cell's DNA and the cell loses its ability to know when to stop growing and replicating. Normal cells know when they need to start growing and when they have to stop, cancerous cells only know how to grow and keep growing without control. This uncontrolled growth is a feature of all cancers, and as the cancer grows it destroys the healthy tissue around it by growing into, and replacing healthy tissue with cancerous tissue. The growing cancer can also invade blood vessels and nerves and spread to distant organs in this fashion. This is called metastasis.

The three most common types of skin cancer in Canada are:

  • Basal Cell Cancer (1 in 8 lifetime risk)
  • Squamous Cell Cancer (1 in 20 lifetime risk)
  • Malignant Melanoma (1 in 60 for men, 1 in 70 for women lifetime risk)

Below are some photo examples of skin cancer, and their view through the dermatoscope