Skin cancer diagnosis and treatment

Once a skin cancer has been diagnosed, the treatment will depend on the type of skin cancer, the size, the location, and the number to be treated.

Most skin cancers are treated by cutting out the lesion entirely and by removing sufficient of the surrounding tissue to be sure that all the cancer has gone and the edges are free of cancerous cells. This can mean removing a 2 centimetre margin around the spot. Surgery has the highest overall cure rate for both early and high risk cancers.

Lower risk cancers

For lower risk cancers, such as squamous and basal cell carcinomas, there are several other treatments that can be used, but they will only provide adequate control for low risk cases.

• Curetting and cauterising – The cancer is scraped out (using a tool called a curette) and the wound is cauterised (burned to stop the bleeding).

• Moh’s controlled excision – The cancer is removed with a smaller amount of surrounding tissue and the excised tissue is examined for cancer cells under a microscope while the patient is still in the operating room. Further tissue is then removed and examined layer by layer. It may take several ‘slices’ before the microscopic examination no longer shows signs of cancerous cells.

• Cryotherapy (freezing) – Liquid nitrogen can be used to freeze off small cancers.

• Radiotherapy (X-ray treatment) – Radiation (most commonly X-rays) is directed to the target tissue and transmits energy that damages and destroys the cancer cells. Of course, this will also damage normal cells, but they are able to recover from the damage. Radiation may be used after the removal of a high risk cancer.

• Photodynamic therapy – Photosensitising drugs, oxygen and light are used to create a photochemical reaction that destroys the cancer cells. This can be used for superficial basal cell and squamous cell carcinomas.

• Chemotherapy – If the cancer has spread (metastasised), chemotherapy may be required. This is treating the cancer with chemicals that kill cells. Broadly, chemotherapeutic drugs work by impairing cell division, effectively targeting the fast dividing cancer cells. Unfortunately, this means that other fast dividing cells, such as those responsible for hair growth, are also affected.

Excision of a carcinoma

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Surgical excision of a carcinoma.

Rights: Eileen O'Shea

Melanoma

Melanoma is the most serious skin cancer because it can readily spread to other parts of the body (metastasise). It also the most difficult to treat. Surgery is the primary treatment at all stages of a melanoma. Complete removal of the melanoma before it has spread is the only possible cure.

Lymphoscintigraphy in the armpit

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Lymphoscintigraphy showing a sentinel lymph node in the armpit. A radioactive tracer has been injected at the tumor site in order to identify the sentinel node(s). A blue tracer dye has also been used for greater accuracy of identification. The node will be removed and biopsied.

Rights: Will Blakem GNU Free Documentation Licence

A biopsy of the removed tissue will determine how deeply into the skin the melanoma has gone. This is called the Breslow's depth. In general, the thinner the melanoma, the better the outcome. In its earliest stages, melanoma cells are only found in the outer layers of the skin and don’t invade the body. It is more advanced if the melanoma is thicker than 4 mm. Some types of melanoma develop quickly over a period of weeks or months (they become thick fast), while others develop over months or sometimes even years.

Melanomas that spread usually do so to lymph nodes first. A technique called lymphoscintigraphy can be used to identify the sentinel lymph nodes – the lymph node(s) that the cancer cells have drained to first – and these lymph nodes can be removed. However, the survival rate for metastasised melanoma is less than 10%. The median survival is 6–12 months.

Chemotherapy has not been found to be very effective for melanoma – although occasionally it does work very well. Radiation shrinks and slows – but does not usually cure – melanoma. Once melanoma has metastasised, the cancer is generally considered incurable.

Research is ongoing into future possible treatments for all types of skin cancer. In Sea sponges and rongoā, discover how a natural compound found in sea sponges has the potential to be a powerful anti-cancer drug. It is part of the Project Mātauranga television series that investigates Māori world views and methodologies within the scientific community.