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Premalignant skin lesions

Dr Martyn Richards offers advice on how GPs can ensure they do not miss skin conditions that

may develop into cancer

There are a range of different skin conditions that present to GPs which have the potential for malignant transformation or invasion. An awareness of which skin lesions have the potential for cancerous change is a crucial first step to ensuring GPs deal with them appropriately.

Solar keratoses are the commonest premalignant skin lesions seen in general practice. The UK prevalence of solar keratoses in pateints aged over 70 is reported to be as high as 52 per cent.

Cutaneous horns have perhaps the greater chance of transformation into invasive

squamous cell cancer (SCC). Lentigo maligna (Hutchinson's freckle) may change into malignant melanoma in elderly patients.

Solar keratoses

These skin lesions are so commonly seen in general practice they are almost taken for granted. Early lesions occur at sun-exposed sites and are sometimes harder to see than to feel, as rough patches of skin. They appear clinically as inflamed areas with some surface roughness and scale .

Fair-skinned Celtic individuals are at particular risk of developing numerous lesions unless they use adequate UV protection throughout life. The evidence suggests the risk of malignant transformation into squamous cell carcinoma is about 1/1000.

Treatment options for non-suspicious solar keratoses include diclofenac sodium gel, cryotherapy, fluorouracil cream or curettage and cautery.

This presentation should alert the GP to potential sinister change in a pre-existing solar keratosis. Note the induration and inflammation of the central part of the lesion. Excision biopsy confirmed the clinical suspicion that this had changed into an invasive squamous cell carcinoma .

In many solar keratoses it is impossible to exclude SCC changes clinically so it is prudent to biopsy them whenever there is any doubt.

Lentigo maligna

These pigmented lesions are usually found on the cheek areas of elderly patients. They are also known as Hutchinson's freckle.

After considerable time lentigo maligna may undergo malignant change into a melanoma proper.

Clinically suspicious signs include darkening or nodularity changes within them (see left).

Cutaneous horns

These horn-like lesions are made up of hard keratin. They are thought to develop from dysplastic areas of skin, usually as a result of chronic UV damage. Long-standing lesions may develop into squamous cell tumours at their base.

Histology reveals that about 15 per cent of cutaneous horns may reveal SCC changes. Clinical suspicion should be alerted when the base of a cutaneous horn is inflamed, indurated or bulbous in appearance (above ).

Clinically suspicious cutaneous horns should be excised because of the risk of SCC. Benign-looking horns can be removed by curettage and cautery but always check the histology.


This 65-year-old woman was concerned about a fast-growing dome-like lesion on her right cheek. It had developed over the previous six weeks.

There was no pain but the patient was worried about knocking it when washing her face. This case is a typical appearance of a keratoacanthoma. Note the central plug of keratin in the dome- like base. These lesions may initially enlarge rapidly but some will regress leaving only a scar.

However, some may develop squamous cell carcinomas in the base. It is impossible to predict clinically which ones may involute so it is my practice to encourage removal of these lesions by thorough curettage and cautery.

Histological examination of these lesions is difficult; it will help the pathologist if the dome-like lesion is kept as intact as possible during surgical removal.

Bowen's disease

This is an intraepithelial carcinoma with SCC in-situ in the epidermis. When the basement membrane of the epidermis is breached it can lead to invasive SCC. The malignant potential is estimated to be about

8 per cent .

This condition can look like psoriasis or eczema, with defined red scaly lesions, often with an irregular edge. It is common on the legs of elderly patients.

This well-defined red scaly macule is typical of Bowen's disease. Note how the defined edge is irregular in shape.

Any areas of induration or inflammation should be regarded as clinically suspicious as they may indicate transformation into invasive SCC.

The lesion should be excised in any case where there is any doubt.

Treatment options

for Bowen's


lGentle cryotherapy (caution on leg lesions in elderly patients – too much vigour may lead to poor healing or leg ulceration)

lFluorouracil cream (carefully applied twice daily for three-four weeks)

lCurettage and cautery

lExcise if suspicious


Squamous cell cancers cause around 500 deaths every year in the UK. SCC can originate from some of the lesions shown so vigilance is necessary on the part of both GPs and patients.

GPs should assess any skin lesion critically and have a low threshold for concern if they exhibit any potentially sinister signs.

Martyn Richards is a GP in Yeovil, Somerset, who also works as a

GPwSI in dermatology

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