Bowen's disease (squamous cell carcinoma in situ)

Most cases of SCC in situ develop as a result of long-term sun exposure.  People who have a weakened immune system and are on long term immunosuppression medication are more likely to get SCC in situ. Very occasionally, SCC in situ may develop after radiotherapy, longstanding arsenic ingestion (very rare nowadays) or due to the human papillomavirus (a common virus that can cause viral warts). SCC in situ is not infectious and is not caused by an allergy.

Is squamous cell carcinoma in situ hereditary?

No, but some of the factors that increase the risk of getting it, such as a fair skin and a tendency to burn in the sun, do run in families.

A patch of SCC in situ starts as a small red scaly area on the skin, which grows very slowly. It may reach a diameter of a few centimetres across. It commonly occurs on skin that has been exposed to the sun, especially the face, scalp, and neck, as well as the hands and lower legs. There may be more than one area of skin affected. The development of an ulcer, lump or pain within a patch, may indicate the formation of invasive squamous cell cancer.

What are the symptoms of squamous cell carcinoma in situ? 

Often there are no symptoms, although the rough surface may catch on clothing.

Images DermNetNZ.

A patch of squamous cell carcinoma in situ can look rather like other scaly skin conditions, such as psoriasis. For this reason, it is often examined under a dermatoscope (a magnifying tool used to examine the skin). Sometimes a biopsy (a small sample of skin) may be taken to make the diagnosis.

Can it be cured?

Yes. SCC in situ is confined to the surface of the skin and there are a variety of ways in which it can be removed (see below). 

How can it be treated?

Several treatments are available for Bowen's disease:

A particular problem with SCC in situ is that it frequently occurs on the lower legs. The skin on the lower legs is often tight and sometimes quite fragile, especially in older people. Healing in this area is slow. Many factors, therefore, play a part in selecting the right treatment:

• The size and thickness of the affected patch
• The number of patches
• Whether there is swelling of the legs
• The general condition of the skin on the legs
• The patient’s preference

If your dermatology team thinks that the area is small and unlikely to cause problems, you may have to be observed in a clinic or by your GP.

From now on, you should take precautions to prevent additional patches of squamous cell carcinoma in situ developing:

• Check your skin regularly for new patches
• The smaller your patch of squamous cell carcinoma in situ is, the better the results of treatment are likely to be. If you think another patch is developing, see your doctor about it promptly.
• If the patch changes in any way (e.g. bleeds, ulcerates or develops a lump) contact your doctor as soon as possible as this could be the start of an invasive skin cancer.

Top sun safety tips

Sun protection is recommended for all patients. It is advisable to protect the skin from further sun damage (for example, by wearing a hat, long sleeves and a sunscreen with a high sun protection factor).

Vitamin D advice

The evidence relating to the health effects of serum vitamin D levels, exposure to sunlight and vitamin D intake, is inconclusive. People who are avoiding (or need to avoid) sun exposure may be at risk of vitamin D deficiency and should consider having their serum vitamin D levels checked. If the levels are low, they may consider:

• taking vitamin D supplements of 10-25 micrograms per day
• increasing intake of food rich in vitamin D such as oily fish, eggs, meat, fortified margarine and cereals.