The major risk is from ultraviolet (UV) radiation/light from the sun and sunbeds. The UV damages the genetic material in skin cells (DNA) leading to abnormal cell growth. These abnormalities can increase over time meaning that sun damage as a child or in early adulthood becomes apparent in later life. This is especially true for people with paler skin which, when exposed, tends to go red rather than tan. Non-melanoma skin cancer also seems to be associated with overall sun exposure through life, eg outdoor work, sports and hobbies. Darker skinned people have lower skin cancer rates because the pigment in their skin, (melanin) protects the cells from UV to some extent, but they do still sometimes get skin cancers.
Certain skin cancers, particularly squamous cell carcinoma, can be caused by long term irritation from sources other than sunshine such as chemicals or oils, long-standing ulcers, burn and scar tissue, and radiotherapy sites.
The effectiveness of the body’s own defence system can be reduced (immunosuppression) by some drugs, such as those taken after transplant surgery, or by other illnesses. This can increase the risk of developing a skin cancer. The importance of taking immunosuppressants far outweighs the potential risk of skin cancer, but transplant patients should see a skin specialist every year for a skin check.
Having had one skin cancer identifies a person as being more at risk of developing another later in life.
Most non-melanoma skin cancer does not run in families. In some very rare cases melanoma may have a genetic family link. However, any familial risk of developing a skin cancer may be related to sharing the same skin type (pale, freckly or having lots of moles) or having had similar sun exposure (lived abroad, holidays).
Some families have skin types with very many moles with different colour, shape and size. Most of these will not turn into skin cancers but people with this sort of skin type are at an increased risk especially where they have more than 50 moles and a close family member has had melanoma. This is known as FAMMM (familial atypical multiple mole melanoma syndrome).
Non-melanoma skin cancers (NMSC)
There are some very rare inherited conditions that increase the risk of NMSCs.
Xeroderma Pigmentosum (XP)
This condition causes problems in skin cell DNA repair after damage so that UV exposed skin becomes more prone to NMSC.
This inherited condition, present from birth, increases the risk of BCC so they occur in greater numbers and at an earlier age than would otherwise be the case.