Understanding common types of skin cancer.

Basal cells are located at the bottom of the epidermis, the outer layer of the skin. Their role is to create new skin cells as older cells move toward the surface. Basal cell carcinoma develops when DNA in these cells is damaged, most often from long-term ultraviolet (UV) exposure. It is the most common type of skin cancer and rarely spreads to other parts of the body.

What to watch for

• Pinkish growths

• Open sores

• Shiny or pearly bumps

• Red patches or dome-shaped lesions

• Spots that may crust, itch, ooze, or bleed

Melanoma begins in melanocytes, the cells that produce melanin (the pigment that gives skin its colour). Sun exposure can influence how melanocytes behave, and having a large number of moles or certain genetic factors can increase a person’s risk of developing melanoma. In men, melanoma is often found on the back, head, or neck, while in women it more commonly appears on the lower legs or back. Melanoma is considered serious because it can spread to other parts of the body if not detected and treated early.

What to watch for

• Asymmetrical moles or spots with two different-looking halves

• Changes in colour, including multiple colours or unusual patterns

• New or changing lesions larger than 6 mm (about 1/4 inch)

• New symptoms such as itchiness, tenderness, or bleeding

• Borders that look irregular, notched, or scalloped

Merkel cell carcinoma (MCC) is a rare form of non-melanoma skin cancer that begins in Merkel cells, which are located in the upper layers of the skin and within hair follicles. MCC most often appears on areas that receive a lot of sun exposure, such as the head, neck, arms, and legs. It is considered a serious skin cancer because it can grow and spread quickly, making early assessment important.

What to watch for

• A slightly raised spot or dome-shaped lesion that may resemble a sore or lump
• Lesions that may appear red, pink, blue, or purple in colour

Squamous cells are one of the three main cell types in the epidermis, the outer layer of the skin. They are flat cells located near the surface and are continually replaced as the skin renews itself. Squamous cell carcinoma (SCC) develops when the DNA in these cells becomes damaged—most often from long-term ultraviolet (UV) exposure, though other factors can also contribute.

What to watch for

• A firm, red nodule

• A flat sore with a scaly crust

• A new sore or raised area that appears over an older scar or ulcer

• A scaly or rough patch on the lip

• A persistent reddish or rough area inside the mouth

Topical chemotherapy cream is applied directly to the skin in the area being treated. Because the medication works on the surface of the skin, it does not carry the same systemic effects seen with traditional chemotherapy.

This treatment is commonly recommended for precancerous lesions, such as actinic keratoses or Bowen’s disease, and may be considered for some superficial skin cancers, depending on your physician’s assessment.

While this option can be effective, the treatment period is longer and may cause temporary skin irritation, which some patients find uncomfortable.