Skin cancer is a disease in which malignant (cancer) cells form in the tissues of the skin. The skin is the body’s largest organ. It protects against heat, sunlight, injury, and infection. Skin also helps control body temperature and stores water, fat, and vitamin D. The skin has several layers, but the two main layers are the epidermis (upper or outer layer)
and the dermis (lower or inner layer).
Skin cancer begins in the epidermis, which is made up of 3 kinds of cells: Squamous cells: Thin, flat cells that form the top layer of the epidermis. Basal cells: Round cells under the squamous cells. Melanocytes: Found in the lower part of the epidermis, these cells make melanin, the pigment that gives skin its natural color. When skin is exposed to the sun, melanocytes make more pigment, causing the skin to tan, or darken.
Causes of Skin Cancer
Ultraviolet (UV) radiation from repeated bouts of sun exposure is believed to be the main preventable cause of skin cancer. Energy from the sun is actually a form of radiation, with the ability to cause damage to living cells. Solar energy consists of visible light and other rays that can’t be seen with the naked eye. Infrared radiation, for instance, makes sunlight feel hot. Ultraviolet radiation causes sunburn and sun tan. UV radiation causes damage to the skin cell DNA, the genetic material of the cells. DNA controls the growth and overall health of skin cells. If the DNA damage is severe, a normal skin cell may begin to grow in an uncontrolled and disorderly way and turn into a cancer. UV also can cause sunburn, and other damage that makes the skin look prematurely old and wrinkled.
Types of skin cancer
Skin cancer affects people of all skin tones, including those with darker complexions. When melanoma occurs in those with dark skin tones, it’s more likely to occur in areas not normally considered to be sun-exposed.
A cancerous skin lesion can appear suddenly or develop slowly. Its appearance depends on the type of cancer.
Basal cell carcinoma
This is the most common skin cancer. It’s also the most easily treated and the least likely to spread. Basal cell carcinoma usually appears as one of the following:
• A pearly or waxy bump on your face, ears or neck
• A flat, flesh-colored or brown scar-like lesion on your chest or back
Squamous cell carcinoma
Squamous cell carcinoma is easily treated if detected early, but it’s slightly more apt to spread than is basal cell carcinoma. Most often, squamous cell carcinoma appears as one of the following:
• A firm, red nodule on your face, lips, ears, neck, hands or arms
• A flat lesion with a scaly, crusted surface on your face, ears, neck, hands or arms
Melanoma
This is the most serious form of skin cancer and the one responsible for most skin cancer deaths. Melanoma can develop anywhere on your body, in otherwise normal skin or in an existing mole that turns malignant. Melanoma most often appears on the trunk, head or neck of affected men. In women, this type of cancer most often develops on the arms or legs.
Warning signs of melanoma include:
• A large brownish spot with darker speckles located anywhere on your body
• A simple mole located anywhere on your body that changes in color, size or feel or that bleeds
• A small lesion with an irregular border and red, white, blue or blue-black spots on your trunk or limbs
• Shiny, firm, dome-shaped bumps located anywhere on your body
• Dark lesions on your palms, soles, fingertips and toes, or on mucous membranes lining your mouth, nose, vagina and anus
Treatments for Skin Cancer
Surgery is an important treatment for many skin cancers. Surgery can be done in a variety of ways. Small cancers can usually be removed under local anaesthetic.
When larger tumours are removed, skin grafts or flaps are sometimes needed to replace the removed skin. A skin graft is a thin layer of healthy skin taken from another part of the body. This is done under either a local or general anaesthetic. In many cases, surgery is the only treatment needed. Rarely, patients with squamous cell skin cancers will also have surgery to remove nearby lymph nodes .
Radiotherapy may be used instead of surgery. It can be a very effective alternative for basal and squamous cell cancers. Radiotherapy is often used in areas of the face where surgery might be difficult or cause unacceptable scarring. However, its use is not recommended in young people as it causes skin damage which becomes more visible over the years.
Radiotherapy may be given after surgery if there is a risk that some cancer cells may still be present. Sometimes it is used for tumours that have grown into the deeper layers of the skin.
Cryotherapy destroys cancer cells by using liquid nitrogen to freeze them. It is a very quick way of treating small, low-risk skin cancers.
Photodynamic therapy (PDT) is a newer treatment for skin cancer. It uses light sources, combined with a light-sensitive drug (sometimes called a photosensitising agent) to destroy cancer cells.
Topical chemotherapy Some early squamous cell carcinomas (SCCs) and superficial BCCs can be treated using a chemotherapy cream, containing a drug called 5FU (Efudix®). The cream is applied directly to the skin cancer and it works by destroying the cancer cells.
Topical immunotherapy Another cream that is used to treat some BCCs and SCCs uses the immune system to attack the cancer cells. The cream is also applied directly to the skin cancer and is known as imiquimod (Aldara®).
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