Sunshine makes us feel better but it can also cause us a lot of damage. This month Susannah Baron discusses how to manage malignant melanoma

The storm clouds have lifted and summer has finally arrived. So begins the British seasonal madness of throwing off clothing, exposing as much sun starved flesh as possible to any available rays, and joining the huge traffic queues heading to the coast.

The summer brings a variety of problems for the dermatologist. Many skin conditions such as psoriasis, eczema, and acne improve with ultraviolet exposure, although everyone is different and some people find that their skin rashes flare in the sun. The summer can also be a particularly difficult time for some people who often find it embarrassing to remove clothing, thus making their rashes visible to the not always sympathetic public. People with psoriasis have been asked to get out of public swimming baths and children are sometimes pulled away from people with skin conditions as parents wrongly assume that the rash is catching.

The sun can bring out a variety of other problems, from sunburn to phytophotodermatitis (don't panic: phyto=plant, photo=light, and dermatitis=skin rash). This often acute and vesicular rash develops in sun exposed areas after someone has had contact with a particular phototoxic provoking plant-for example, giant hogweed or rue.

Polymorphic light eruption is a common sensitivity to ultraviolet light, which results in a pruritic eruption on exposed areas, classically 24 to 48 hours after sun exposure. This can be prevented in subsequent years by having a course of ultraviolet light before the summer.

Many skin diseases are worsened by Sunshine - for example, lupus erythematosis and porphyria, and many drugs are photosensitising - for example, phenothiazines, tetracyclines, sulphonamides, and amiodarone.

Dermatologists are always advising sun protection as ultraviolet exposure stimulates moles and is implicated in all forms of skin cancer: basal cell carcinomas, squamous cell carcinomas, and malignant melanomas. Sadly, although the risks of cancer are well known people still sunbathe. It is often the mention of the photo ageing effects of ultraviolet light that encourages people (especially women) to change behaviour.

Case history

A 32 year old man comes to see you in clinic concerned about a mole on his thigh. He tells you that the lesion was not present until two to three months ago and it has increased rapidly in size in the past three weeks and has become darker in colour.

Questions

• What other points would you like to cover in the history?
• What examination would you like to do?
• What is the diagnosis and differential diagnosis?
• What is your management plan?

Answers

It is important to ask about sun exposure. This man had lived in Australia, had excessive sun exposure, and remembered being sunburnt on numerous occasions. It is also important to ask about family history of melanoma as familial cases can occur. The four important points in the history of the lesion are:

• Change in size
• Change in colour
• Change in shape
• Symptoms (itching, bleeding, etc)

The lesion should be measured and a description recorded - for example, irregular margins, irregular pigmentation, and nodular areas. You should note and examine all other pigmented naevi, feel for any regional lymphadenopathy, and examine for hepatomegaly.

This lesion is a malignant melanoma. It measure 7.5 mm by 8.6 mm. The differential diagnosis is a dysplastic naevus.

The malignant melanoma should be excised urgently and then examined histologically. The depth to which the malignant melanocytes have invaded is the most important prognostic factor for the patient. This measurement, which is made in millimetres, is called the Breslow thickness. This melanoma had a Breslow thickness of 0.7 mm. Current recommendations for surgical excision margins are set out in the table.¹

There are approximately 10 new cases of melanoma per 100 000 of the population a year in Europe and the United States, with a greater incidence in Australia and New Zealand. It is important to follow up patients whose melanomas have been excised. The main objectives are to detect early recurrence, to detect any new primary lesions, and to reinforce educational advice regarding sun exposure. At each follow up visit patients should have a full skin examination and an examination of regional lymph nodes. Follow up with clinical photographs may be helpful if patients have multiple or atypical naevi. There are no firm recommendations regarding frequency of follow up, but it is suggested that patients with melanomas greater than 1 mm in Breslow thickness should be followed up for five years and those with thinner lesions can be discharged after three years.