what causes it?

The risk of getting an SCC is higher:

• with repeated, long-term exposure to sunlight. Ultraviolet (UV) light from the sun (or from sun beds) damages DNA, the stuff that holds the genetic code in body cells. Damage to DNA can cause normal cells to mutate and become cancerous. This is the main cause.
  
  
• with age. It is more common in people over 60.
  
  
• with lifestyles where people are out in the sun a lot. Builders, farmers surfers, sailors and people who often use sun beds can develop SCCs while still quite young.
  
  
• if you are fair-skinned, light-haired, blue-eyed, freckly or have a tendency to burn rather than tan. Darker skinned people have more natural protection against UV light.
  
  
• if you have previously had SCC. This is because you have already had significant damage to your skin from sunlight.
  
  
• if you have actinic keratosis or Bowen’s Disease, you have a slight risk that it may change to SCC.
  
  
• if your immune system has been suppressed by medication taken after organ transplant, or by treatment for leukaemia or lymphoma.
  
  
• if you have had a lot of PUVA, a type of ultraviolet A light treatment, for skin conditions such as psoriasis.
  
  
• if you have had previous x-ray treatment or exposure to nuclear radiation or infra-red radiation. There is a time-lag of 10-40 years after exposure before the harm is evident.
  
  
• if you smoke tobacco. This increases the chances of a SCC on the lips.
  
  
• if you have either xeroderma pigmentosum or albinism, two rare hereditary conditions. SCC itself is not hereditary.
  
  
• if you have taken something containing arsenic (many years ago some ‘tonics’ contained arsenic, and some older people may have taken one in childhood).
  
  
• if you are infected with the human papillomas virus (HPV). It is linked to anal and genital SCC.
  
  
• if you have been exposed to toxins from coal tar and mineral oils (polycyclic aromatic hydrocarbons).
  
  
• if you have had an ulcer or an inflamed sore or scar for a long time, an SCC may develop on the site of the sore.

You can not catch SCC by contact with someone who has it.

How these risk factors cause SCC are not completely understood. Having one or more of them does not mean that you will develop SCC. It just increases the possibility. If you are concerned about your risk, speak to your GP about it.