Most skin cancers come from over-exposure to UV light. This is usually from sun exposure, but can also be UV light from man-made sources, like tanning beds.

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The most common type of skin cancers are slow growing, but if untreated they can invade bone or other areas under the skin.

Cancers that develop from the pigment-making cells of your skin are called melanomas. They are fast growing and aggressive, and they show up first as a mole or freckle that has changed shape or colour. Melanoma is the fourth most common cancer in New Zealand.

In more detail

The most common types of skin cancers are keratinocyte carcinomas or keratinocyte cancers. They are called this because the cells resemble keratinocytes, the most common cell found in normal skin. Most keratinocyte cancers are either basal cell carcinomas or squamous cell carcinomas.

Basal cell carcinomas make up 80% of all skin cancers, and usually develop on sun-exposed areas, especially the head and neck. These cancers tend to grow slowly but without treatment can grow into nearby areas, like bone or other tissues beneath the skin. After treatment, basal cell carcinoma can often reappear in the same place.

About 20% of skin cancers are squamous cell carcinomas. These cancers commonly appear on the face, ears, neck, lips, and backs of the hands. They can also develop in scars or chronic skin sores. They tend to grow and spread more than basal cell cancers, invading fatty tissues beneath the skin, lymph nodes and sometimes other parts of the body.

Keratoacanthomas are dome-shaped tumours that are found on sun-exposed skin. Many shrink or even go away without any treatment. But some continue to grow, and a few may even spread to other parts of the body. Less common types of skin cancer account for less than 1% of non-melanoma skin cancers, including merkel cell carcinoma, kaposi sarcoma and cutaneous lymphoma.