Is it a melanoma?

Dr Niall Cameron highlights some of the pitfalls in assessing the simple mole

TOWARD the end of a straight-forward consultation, your tenth patient that afternoon adds: “by the way doctor my wife said I should show you this”. “This” being a small slightly pigmented spot on his shoulder. “I think it has always been there but I’m not sure if it has changed. I wasn’t going to bother you but you hear a lot about skin cancer these days.” Some minutes later and now running late you have come to the conclusion that it probably is really nothing, but a dictaphone is at hand and a referral ensues.

Some weeks later a dermatology clinic letter informs you that a wide excision biopsy revealed a superficial spreading melanoma that has been completely excised. How to react? Congratulate yourself on your razor-sharp clinical acumen, have a philosophical discussion over coffee with colleagues about complexity and managing uncertainty or anxiously try to recall all the patients with equally benign looking skin lesions that you have simply reassured?

Very few GPs will not have experienced doubt or anxiety when a patient presents with what on first inspection appears to be a simple mole. Moles are extremely common – present either from birth or appearing later in life. Some can be relatively large and unsightly but the vast majority will be benign and require no intervention.

However, malignant melanoma is a relatively common cancer and it is also likely that most GPs can remember a patient who presented with an obvious melanoma. Differentiating between potential melanomas and simple pigmented lesions is a challenging but important task for GPs. The dilemma is how to ensure you don’t miss a melanoma whilst not referring every pigmented lesion encountered.

Knowing the risk

In 2003 it was reported that 95 per cent of skin lesions referred to a dermatology specialist were benign and a more recent study reported that GPs only recognised 66 per cent of skin malignancies. Appropriate referral has obvious clinical and resource implications. Failure to refer or arrange appropriate review is not an uncommon cause of complaint or even litigation. Unfortunately this is often exacerbated by a failure to make appropriate notes of the consultation.

The incidence of malignant melanoma has risen in most Caucasian populations over the last 30 years, and Australia and New Zealand have the highest incidence in the world. Malignant melanoma is the third most common tumour in people aged 15-39 but the incidence increases with age and melanoma is most often diagnosed over the age of 60.

Melanomas can develop both in normal skin and existing moles. The majority of moles appear later in life and are classified as acquired melanocytic naevi. Moles which have been present from birth (congenital naevi) can be quite large, typically over 1 cm in diameter, tend to get bigger through life and are often dark and hairy. However, the risk of malignant change in pre-existing moles is well recognised and assessing the significance of this change is perhaps the most important challenge for GPs.

Melanoma is the least common form of skin cancer but it is the most serious and likely to spread. Prognosis can be significantly improved by early detection and this has resulted in an emphasis on early recognition and referral of suspicious pigmented lesions.

The main risk factor is sun exposure – particularly in childhood. It is worthwhile asking about time spent abroad when young and the association is greatest with a history of severe sunburn. Sun bed use should also be considered. People with fair skin that burns easily or never tans, blonde or red hair and blue or green eyes also have an increased risk of melanoma. A freckled complexion or more significantly large numbers (over 100) of common naevi are recognised risk factors. The presence of more than two atypical moles (bigger than usual with irregular shape or colour) is also significant. Other recognised risk factors include a family history of melanoma, particularly in first-degree relatives.

Making a diagnosis

Melanomas can present in a wide range of colours, including light or dark brown, black, blue, red, light grey and occasionally can be non-pigmented; however, most melanomas will begin as a darker often small area of skin with the appearance of a slightly unusual freckle or mole. In women, melanomas occur more commonly on the legs (40 per cent) whereas in men the most common site is the back (40 per cent).

Suspicion should be raised if there is a change in size, particularly over a short period such as weeks or a few months. Melanomas are often asymmetrical in appearance, have a ragged border and although initially flat become thickened and raised. Any change in colour or the presence of inconsistent pigmentation is significant. Bleeding and crusting are late signs but are often present in advanced lesions. In contrast benign moles usually grow slowly, are round and even, and have a uniform colour and edge.

As in all areas of medicine, careful history and examination can help to reduce diagnostic uncertainty and ensure appropriate referral. The emphasis on early diagnosis has led to the development of useful guidelines to aid prompt recognition of suspicious changes. Reference to the criteria in these guidelines will also help to reduce the risk of complaint as they highlight features that should be recorded and signpost essential patient advice.

The Glasgow seven point checklist was introduced in 1991 and identified major and minor suspicious features that should be looked.

Major features Minor features
• Change in size • Oozing
• Irregular shape • Change in sensation
• Irregular colour • Inflammation
  • Diameter > 7mm

The ABCDE checklist followed and offers a useful template for documenting a consultation with a patient with a pigmented lesion.

  • Asymmetry – uneven or asymmetrical shape
  • Border – a ragged outline
  • Colour – inconsistent pigmentation
  • Diameter – >6mm and usually continues to grow
  • Evolving – any new symptom such as ching or change in size, shape or colour.

Not all patients will present with these signs and where patients have a number of moles they may share a broadly similar appearance. However, a melanoma will often have a different pattern than other naevi and this has been described as the ”ugly duckling sign” and should prompt referral.

Making the referral

Suspicious lesions should be referred urgently for specialist review within two weeks and most dermatology clinics offer an urgent pigmented lesion service. Removal with wide excision biopsy allows accurate staging if melanoma is diagnosed. Staging and prognosis are dependent on the thickness of the melanoma, whether the surface is ulcerated and evidence of local or distant spread. Prognosis is good in lesions confined to the dermis but penetration beyond the dermis and distant spread indicates a high risk of recurrence and a poor prognosis.

Patients with an atypical naevus (the ugly duckling) or a large number of common naevi should be referred for specialist assessment, and annual photographic surveillance is now commonly used. Patients with obviously benign lesions can be reassured but should be given clear advice about self examination and sun protection.

Patients without an obvious melanoma at first inspection may need follow-up in primary care, and careful recording of the appearance of the lesion including measurement is important. The timescale for arranging review is likely to be dependent on the level of doubt and patient anxiety. The possible rapid progression of melanoma should be borne in mind and follow-up arrangements should be clear and documented. Digital photography against a ruler is a reasonable precaution. Dermoscopy (an illuminated magnifying device) is commonly only used by doctors with a special interest in dermatology who have been trained in the technique.

Biopsy of pigmented lesions is inappropriate in general practice unless the doctor has received proper training and appropriate facilities are available. Moles should never be treated with cryotherapy.

Managing uncertainty in general practice is a perennial and challenging problem that is exacerbated by continuing pressure to refer appropriately whilst minimising risk. When dealing with pigmented lesions GPs should continue to refer for specialist review where doubt exists.

Dr Niall Cameron is a GP and medico-legal expert in primary care

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