The body is made up of different types of cells that normally divide and multiply in an orderly way. These new cells replace older cells. In case of cancer, certain cells in the body have changed in appearance and function. They divide and grow in an uncontrolled way causing cancer. Skin cancer is a disease where malignant cells are found in the epidermis (outer layer of the skin). Skin cancers can develop due to a continuous exposure to sun over the years.

Skin is the largest organ of the body and protects the body from injury and infection. It also regulates the body temperature and gets rid of waste substances through the sweat glands. Outer layer of the skin is called the epidermis and the layer underneath is known as the dermis. The epidermis contains the squamous cells, which are flat in shape. Below this layer are the basal cells, which appear round. In between these layers are the melanocytes, which produce the pigment, melanin that gives color to the skin.

Sunburn and Ultra Violet light exposure causes maximum damage resulting in DNA damage to the skin. The body can usually repair this damage before gene mutations occur. But when a person’s body cannot repair the damaged DNA, then it results in skin cancer. It is likely that most skin damage from ultraviolet radiation occurs before the age of 20. It is thought that a gradual build-up of overexposure to the sun over a period of several years can lead to the development of basal cell and squamous cell skin cancers.

In some cases about 5-10% of melanomas develop in people with a family history of melanoma. But inherited faulty genes do not cause non-melanoma skin cancers.

The regular use of sunlamps and sunbeds increases the risk of developing skin cancer.

Some of the areas of skin that have been badly burned, or have had long-term inflammation have an increased risk of squamous cell carcinoma.

Radiotherapy given to treat other conditions can sometimes cause skin cancers in the treatment area later in life.

Other possible but rare predisposing factors are overexposure to certain chemicals at work, including coal tar, soot, pitch, asphalt, creosotes, paraffin waxes, petroleum derivatives, hair dyes, cutting oils and arsenic. Protective clothing should be worn during handling these substances.