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An abnormal or uncontrolled growth of the cells of the skin can be benign or malignant. If it's malignant, it's called skin cancer. A malignant growth can invade neighbouring tissues or spread to distant organs in the body (metastasis).
The main types of malignant skin cancer are
- malignant melanoma (MM)
- basal cell carcinoma (BCC)
- squamous cell carcinoma (SCC)
Basal and squamous cell carcinomas are often grouped together and referred to as non-melanoma skin cancer.
The main risk factor for any type of skin cancer is exposure to the intense ultraviolet light of sunshine. It is particularly common in places where the sun is strong such as Australia, and less common in people with dark skin. People at increased risk tend to have:
- a family history of skin cancer
- skin which has a lot of moles
- fair skin and blue eyes
- skin that burns easily
- skin that has been badly sunburned in the last five years
- skin exposed intermittently to strong sunshine (or sun beds)
The skin is made up of three layers: the outer epidermis, the dermis below this and the supporting subcutaneous layer of loose tissue and fat. Cells in any of these layers can be the origin of a cancerous growth.
Problem skin growths
These are not cancers. Benign skin growths include warts, moles, or corns, which are rarely serious problems. There are other, less common benign skin problems that can become malignant. These include:
- Bowen's disease: This is a pre-cancerous skin condition. It looks like a red scaly area of skin, and is restricted to the epidermis. If left untreated, it can develop into a squamous cell carcinoma.
- Actinic keratosis: This is a small lump of hard skin, commonly seen in areas exposed to the sun. The condition is usually harmless, but there is a very small risk of them transforming into squamous cell carcinomas.
Malignant skin cancers
- Basal cell carcinoma (BCC), also known as or rodent ulcer. This is the most common form of malignant skin cancer. A BCC arises from cells in the epidermis. Typically it affects only small areas, grows slowly and does not spread to other tissues. Consequently a BCC is not usually life-threatening. However, if left untreated, the cancerous cells can 'burrow' deeper into the skin, hence the name rodent ulcer. BCC are associated with sun-exposure and often affect the face.
- Squamous cell carcinoma (SCC): This is the second most common malignant skin cancer, and in rare cases it can be life-threatening. It arises from cells in the epidermis and invades the skin locally, but it can also spread to nearby lymph nodes. Squamous cell carcinomas appear as thickened skin, nodule or lump or can appear as an ulcer. SCC can be caused by sun exposure and certain viruses that affect the skin, and can occur in old scars.
- Malignant melanoma: This is the most serious skin cancer and often spreads to other tissues or organs. Although it can develop from moles in the skin, most melanomas arise from a pigment-producing cell found in the epidermis. Melanomas resemble moles on the skin, but there are differences. The following list of features can help distinguish a melanoma from a normal mole.
Asymmetry: The melanoma skin lesion is an irregular shape
Border: The outline of the spot is ragged rather than smooth
Colour: There is a variation of colour within the spot
Diameter: The spot is bigger than 6mm across and/or has increased in size recently
Elevation: The lesion is raised above the surface of the skin
Other features which may indicate skin cancer include any spot that changes in size, shape, or colour; itches, bleeds or forms an ulcer. Although these signs do not necessarily indicate skin cancer, you should visit your doctor to have it assessed.
Diagnosis of skin cancer
If a skin cancer is suspected, your doctor may recommend a biopsy, which involves removing a sample of the skin from the affected area for examination under a microscope. If necessary, you will be referred to a skin specialist called a dermatologist, a cancer specialist (oncologist) or plastic surgeon.
If there is a risk that the cancer may have spread, other tests such as CT or MRI scans, and X-rays may be needed to visualise areas inside the body.
Treatment for skin cancer
Treatment options vary depending on the type and stage of disease.
- Actinic keratosis and Bowen's disease: the area of affected skin is removed, either by freezing with a spray of liquid nitrogen or using a skin cream called 5-fluorouracil . The removed tissue can be examined under a microscope to confirm the diagnosis.
- Basal cell carcinoma can usually be cut away in a minor operation, or removed by freezing with liquid nitrogen. Sometimes radiotherapy or topical (applied to the skin) chemotherapy may be also needed.
- Squamous cell carcinoma is usually removed surgically because of the risk of spread to other sites. Surgery might be followed up with radiotherapy.
- Melanoma: When melanoma involves only the epidermis, this is called melanoma in situ. It can be removed surgically. The surgeon will also remove a ring of normal skin. The deeper the melanoma, the more surrounding tissue needs to be removed. If a large area of tissue is removed then a skin graft might be needed to fill the "hole". If the cancer has spread, chemotherapy and other medications may keep the disease at bay for a while. At this point, treatment is unlikely to cure the condition, and focuses on relieving symptoms and prolonging life. The thicker the melanoma at the time of diagnosis, the more likely the cancer is to have spread.
Prevention of skin cancer
- Be 'sun aware'. To reduce the risk of skin cancer, minimise your exposure to the sun. Always be use sunscreens, wear protective clothing and remain in the shade as much as possible, and especially between 11a.m. and 3 p.m. when the sun is at its strongest. Avoid sun beds.
- Be vigilant: the earlier a skin cancer is identified and treated then the better the outcome. You should show your doctor any skin lesion, which is unusual, new or changing shape as soon as possible.
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