These are precancerous skin conditions caused by too much exposure to the sun. They are usually small, less than a quarter of an inch across, rough or scaly spots that may be pink, red or flesh coloured. Usually they start on the face, ears, backs of the hands and also the legs for older people with fair skin, although they can occur in out of sun exposed areas. People who have them usually develop more than one.

Solar keratoses tend to grow slowly and usually do not cause any symptoms (although some are likely to be itchy or sore). They sometimes go on their own, but they can come back.

A small percentage of them turn into squamous cell skin cancers. Most do not become cancer, but it can be hard sometimes to tell them apart from true skin cancers, so on the whole, they are recommended to be treated.

If they are not treated then they should be checked regularly for changes and likely signs of skin cancer.

Squamous cell carcinoma in situ, also called Bowen’s disease, is the earliest form of squamous cell skin cancer. In situ means that the cells of these cancers are still only in the epidermis, the upper layer of the skin and have not invaded into deeper layers.

Bowen’s disease appears as reddish patches. Compared with solar keratoses, Bowen’s disease patches tend to be larger, redder, scalier and sometimes crusted. Like solar keratoses Bowen’s, disease usually does not cause symptoms, although likely itchy or sore.

Like most other skin cancers, these cancers often appear in sun-exposed areas. They can also occur in the skin of the anal and genital area. This is often related to sexually transmitted infection with HPV, the virus that can also cause genital warts.

Bowen’s disease can sometimes progress to an invasive squamous cell skin cancer, so it is recommended to treat them.

If you have these, you are also at higher risk for other skin cancers so a regular skin check is recommended.

These are dome-shaped tumours that are found on sun-exposed skin. They may start out growing quickly, but their growth usually slows down. They may shrink or even go away on their own over time without any treatment, but some continue to grow and a few may even spread to the other parts of the body. They can be hard to tell from squamous skin cancer and their growth is often hard to predict.

The most important warning sign of a melanoma is a new spot on the skin or a spot that is changing in size, shape or colour, also if it looks different from all of the other spots on your skin. This requires for you to be checked.

The pattern and timing of the UV exposure may play a role in melanoma development. For example, melanoma on the trunk and legs has been linked to frequent sunburns, especially in childhood. This might be related to the fact that these areas are not constantly exposed to UV light.

Some evidence suggests that melanomas that start in these areas are different than those that start on the face, neck and arms, where the sun exposure is not constant.

Also different from either of these are melanomas in the palms of the hands, soles of the foot, or underneath the nails or on the internal surfaces such as the mouth and the vagina.

Having many moles does not cause problems but someone who has many moles is more likely to develop melanoma. This can be because of dysplastic naevi. These are moles, which look like normal moles but also have some features of melanoma. They are often larger than other moles and have a normal shape or colour. Dysplastic naevi can run in families. A small percentage of dysplastic naevi may develop into melanomas. Most dysplastic naevi never become cancer and many melanomas appear to arise without a pre-existing dysplastic naevus.

Atypical naevus syndrome is an inherited condition where you have many dysplastic naevi.

If at least one close relative has had a melanoma, this condition is referred to as familial atypical multiple mole and melanoma syndrome.

People with this condition have a very high lifetime risk of melanoma, so a regular thorough check is important. We sometimes suggest mole mapping in this situation.

Genital melanocystic naevi moles present at birth have a lifetime risk of developing melanoma of between 0 and 5% depending on their size. If you have a very large congenital naevi then there is a higher risk and the risk is lower for smaller.

This results in a higher risk of melanoma for those who are white than for black races. White people with red or blonde hair, blue or green eyes or fair skin, that freckle or burn easily are at an increased risk of developing melanoma.

The risk of developing melanoma is higher if one or more of your first degree relatives has had melanoma.

Around 10% of all people with melanoma have a family history.

This can be related to the fact that there is a shared family lifestyle of frequent sun exposure, a family tendency to have fair skin but certain gene changes that run in families or a combination of the BRCA1 and 2 gene.

A person who has already had melanoma has a higher risk of getting melanoma again.

People who have had basal or squamous cell skin cancers are also at increased risk of getting melanoma.

A person’s immune system helps fight cancer of the skin and other organs. People with weakened immune systems and certain diseases or medical treatments are more likely to develop any types of skin cancer including melanoma, for example kidney transplants, patients are getting medicines that weaken their immune system to prevent them from rejecting the organ.

Melanoma is more likely to occur in older people but it is also found in younger people.

Men appear to have a higher rate of melanoma than women although this varies by age.

Before the age of 50, this is higher in women.

After the age of 50, it is higher in men.

This is a rare inherited condition that affects the skin cells’ ability to repair damage to their DNA. People with this condition have a higher risk of developing melanoma and other skin cancers when young especially on sun-exposed areas of their skin.