What is basal cell carcinoma?
Basal cell carcinoma (BCC) is a type of skin cancer. Together with squamous cell carcinoma, BCC is a type of Non-Melanoma Skin Cancer.
The skin tumours of basal cell carcinoma often look like a small red, pink or pearly lump on otherwise normal skin. Over time they may enlarge, bleed or ulcerate. The tumours are caused by the uncontrolled growth of basal cells at the bottom of the epidermis (the outer layer of skin) and often form in areas of sun-exposed skin. Basal cell carcinomas can spread to other parts of the body (metastasise), but this is very rare.
Basal cell carcinoma is the most common type of skin cancer in the UK. Some studies suggest that there are approximately 100,000 new cases of BCC each year. They account for about 75% of all non-melanoma skin cancers.
Your GP should be able to diagnose it but if in doubt may refer you to a dermatologist.
There are a variety of treatments that range from excision through to photo-dynamic therapy or anti-cancer creams.
Basal cell carcinomas often begin as small, raised lumps which can be red, pink, translucent or pearly. They are more common on areas of sun-exposed skin, with about 80% occurring on the head and neck.
Basal cell carcinomas vary greatly in shape, size and appearance. They may be a few millimetres to a couple of centimetres in diameter.
Sometimes they may be covered with small, dilated blood vessels, known as telangiectasia.
Basal cell carcinomas can also start to bleed, crust or form ulcers. They sometimes form a “rodent ulcer” – where the centre of the ulcer is hard and indented, while the edges are raised and ulcerated.
Some basal cell carcinomas are pigmented and appear black, brown or bluish.
The BCC tumours typically grow very slowly, taking 1 -2 years to grow half a centimetre in diameter.
If left untreated, they can invade and destroy the surrounding skin.
They very rarely spread (metastasise) to other parts of the body, with under 0.5% of basal cell carcinomas thought to metastasise. Larger tumours, however, are more likely to spread.
The main cause of BCC is exposure to UV radiation in sunlight. UV-A and UV-B radiation can penetrate the skin and damage the DNA of basal cells causing them grow and divide uncontrollably. This gives rise to tumours.
People with fairer skin that burns easily, red or blond hair, and green or blue eyes are at higher risk of developing BCC. This is because their skin contains less melanin – a pigment that absorbs and dissipates UV radiation.
Children’s skin is more easily damaged by the sun and so people with large amounts of exposure to sunlight in childhood are at a higher risk of developing a BCC in adulthood. This is particularly true of individuals who have had severe or frequent sunburn and freckling as children.
The main risk factor for developing BCC is exposure to UV radiation from sunlight. People who work outdoors are at particular risk due to increased exposure to sunlight. Using sunbeds, which emit UV radiation, also increases the risk of BCC.
Other risk factors include:
- Family history of skin cancer – this may owe to the fact that characteristics that increase the risk of cancer, such as fair skin and freckling, tend to run in families.
- Having a previous BCC – people with one BCC are at a 44% risk of developing another BCC within three years
- Being male – males are more at risk of developing BCC than females. This gap widens with increasing age.
- Age – those aged 55 are over are at higher risk of developing BCC, presumably due to accumulated sun damage to their skin.
- Suppressed immune system – people with weakened immune system or those taking immunosuppressant medication are at an increased risk of BCC.
- Exposure to certain chemicals – exposure to arsenic has been associated with BCC.
- Rare inherited disorders – BCC is also part of a rare genetic disorder known as Gorlin’s syndrome.
Basal cell carcinoma is usually diagnosed by visually examining the lump on the skin before taking a small sample (biopsy) of the lump to be studied under a microscope. When looking at the skin, your GP may use a special magnifying glass known as a “dermatoscope” to get a closer look.
Biopsies are required to study the cell types in the lump and confirm the diagnosis of BCC. The GP may need to cut out the whole lump – a procedure called an excisional biopsy. This is done under local anaesthetic where the skin is numbed beforehand.
Further tests are not usually required, although a GP may want to order further blood tests and X-rays, CT or MRI to assess whether the basal cell carcinoma has invaded deeper parts of the body.
Referral to a specialist
A GP may refer you to a dermatologist, oncologist, surgeon or other member of a local hospital skin cancer multidisciplinary team (LSMDT) for further treatment of a basal cell carcinoma. An urgent, 2-week referral may be performed for basal cell carcinomas that need more immediate treatment.
The vast majority of BCC cases can be successfully treated by removing the tumour with an excision done under local anaesthetic in your doctor’s surgery. For larger BCCs, BCCs that have invaded underlying structures and BCCs on the face, more complicated surgery may be required. As with all surgical procedures, there is a risk of bleeding.
Non-surgical treatments such as radiotherapy, phototherapy or chemotherapy are sometimes used as alternatives to surgery.
Simple surgical excision
Small BCCs can be surgically removed by a GP in primary care. The procedure is usually done with local anaesthetic, where the skin is numbed beforehand. After the surgery, the incision is usually closed with a few stiches.
Curettage and cautery
This is a surgical procedure that uses a tool called a curette to scrape away the tumour (curettage). Any wounds are sealed and bleeding is then stopped with small burns administered by a high-temperature electric probe (cautery). The procedure has been shown to be safe, and, for smaller BCCs, curettage and cautery cures 90% of cases.
Moh’s micrographic surgery
Moh’s micrographic surgery is a surgical procedure for more aggressive BCCs that have the potential to invade surrounding body structures. It is also used to treat recurrent BCCs and BCCs on the face.
The procedure involves removing the BCC from the affected skin in stages. Once the BCC is first removed, the skin surrounding the excision wound is observed under a microscope to check whether any BCC remains. If some of the tumour is remaining, the procedure is repeated.
Although the procedure has an almost 100% success rate, Moh’s micrographic surgery is time-consuming, requires high surgical expertise and is not available at all hospitals.
Cryotherapy or cryotherapy involves freezing the BCC tumour with liquid nitrogen. This destroys the cancer cells and the tumour eventually falls off. Cryotherapy may cause the surrounding skin to become red, swollen or blistered. This normally subsides within a few days. Cryotherapy is particularly effective in treating BCCs that are nearer the surface of the skin.
Photodynamic therapy is a type of light therapy used to destroy cancer cells. Firstly, a cream containing a chemical known as a ‘photosensitising agent’ is applied to the skin. The skin is then covered and after a few hours the sensitising agent is absorbed by the cancer cells in the BCC. The BCC is then exposed to a bright light for between 10 and 45 minutes. The light is at a specific wavelength that activates the photosensitising agent, causing it to destroy the cancerous cells.
Photodynamic therapy clears about 85% of BCCs that are nearer the surface of the skin. It is less suitable for deeper BCCs. The procedure can cause pain, redness and blistering. These usually settle down after a few days. Less commonly, photodynamic therapy can produce scarring.
Radiotherapy uses a beam of targeted X-rays to destroy the cancerous cells. It may be considered as a treatment for larger or more invasive BCCs, recurrent BCCs or in people who are unsuitable for surgery. Depending on the size and extent of a BCC, a radiotherapy course may last between 2 and 4 weeks.
Radiotherapy has been shown to cure 90% of BCC cases, but the procedure carries a risk of scarring. The skin can also become red and inflamed after radiotherapy, but this usually settles down over time.
Imiquimod is an immune-modulatory drug that triggers the immune system to attack abnormal cells. It is used to destroy the cancerous cells of a BCC. Imiquimod comes as a 5% cream, which is usually applied to the skin daily, for 5 days a week, over a period of 6 weeks.
Topical imiquimod is more suited for treating BCCs that are closer to the surface of the skin. Studies show that imiquimod can cure between 70 and 100% of BCCs, but there is a higher risk that BCCs can reappear when compared to other treatments. The drug may cause redness and soreness of the skin and flu-like symptoms. These generally subside with time.
5-fluorouracil is a drug known as an anti-metabolite. It is taken up by cancerous cells and then interferes with their ability to make and repair DNA, causing them to die. 5-fluorouracil comes as an ointment, which is rubbed onto the BCC affected skin, usually daily for 6 weeks. It is particularly useful for people with more than one BCC, affecting the trunk and limbs. Studies show that is cures about 80% of BCC cases.
Topical 5-fluorouracil commonly causes inflammation of the skin when it is applied. The skin may turn red, blister, crust and weep before it heals. This generally settles down with time and your dermatologist can recommend a variation to the treatment or additional treatments to help cope with the discomfort.
Measures to lower your exposure to harmful UV radiation will help to reduce your risk of developing a basal cell carcinoma. Where possible try to:
- Avoid peak sunlight between 11am and 3pm.
- Wear a sunscreen with an SPF (sun protection factor) of at least 30.
- Wear a hat and cover your body with clothing when exposed to the sun.
- Avoid sunbeds and sunlamps
- Regularly check your skin for any unusual lumps.
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Skin cancer (non-melanoma). NHS Choices (2017). Available online at: http://www.nhs.uk/conditions/Cancer-of-the-skin/Pages/Introduction.aspx
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