Section 1: Epidemiology of melanoma
Over-referral owing to patient pressure and lack of clinical confidence is an increasing problem and, worse still, missed melanoma is not uncommon.
Melanoma incidence has increased dramatically in the past 40 years.1 The current incidence depends on gender and country of residence. In the UK, the risk of melanoma for women and men is one in 110 and one in 150 respectively, while in Australia, incidence is one in 17 for women and one in 14 for men.2
Prognosis also varies with geography. In the UK, the five-year survival for all melanoma is 85 per cent for women and 75 per cent for men, while in Australia, 95 per cent of women and 90 per cent of men survive five years. The only good news seems to be that, in Australia, rates are stabilising and at presentation, the mean thickness (a key prognostic indicator) is falling.3
The causes of melanoma are primarily related to exposure to sun, but constitutional factors are also important. Those at risk include patients with fair skin types, multiple moles and a family history, which is present in 10-15 per cent.
A history of sunburn seems to be a significant risk factor, particularly burning in childhood, as does the pattern of intermittent, high sun exposure with prolonged periods of no exposure that is typical of many package holidays.
Interestingly, regular low-level exposure may be protective, in children at least.4
Melanoma prevention has a long history in Australia. Concerted national efforts to reduce melanoma over the past 25 years may finally be working.5
Fortunately, steps are now being taken to change attitudes to sun protection and it is hoped that the emphasis on children covering up and using sunscreen (see box) will eventually result in a change in adult behaviour in the UK.
Routine advice for sun protection
Section 2: Types of melanoma
Melanoma comes in all shapes and sizes and is broadly classified into five main groups (see box).
Superficial spreading melanoma (SSM) is the most common variant and can occur on any part of the skin at any age. It tends to occur on the lower legs in women and the backs of men, corresponding to patterns of sun exposure.
The lesion may have been present for months, or even years.
Pigmentation is variable and is sometimes entirely absent. Careful history taking in such cases is essential, because patients will often recall a pigmented lesion there in the first place.
By definition, the growth pattern is radial expansion in the first instance, only later invading vertically into deeper structures.
Nodular melanoma (NM) is uncommon, occurring in any site at any age.
Usually the history is shorter. Owing to their rapid growth, they often appear inflamed or even ulcerated and are frequently not pigmented, although a good history will often reveal preceding pigmentation, and sometimes a faint blue/brown colour can be seen at the periphery of the lesion on examination.
NM tends to have a poor prognosis and there may be clinical evidence of metastasis at presentation.
Lentigo maligna melanoma
Lentigo maligna melanoma (LMM) arises within existing lentigo maligna. These usually occur in elderly skin on a background of chronic sun exposure, so tend to arise on the head and neck.
The lentigo maligna may have been present for a decade or more, gradually expanding. There is a sudden change in growth rate as the melanoma becomes invasive.
Prognosis depends on the level of invasion.
Acral lentiginous melanoma
Acral lentiginous melanoma (ALM) is rare in the UK, usually presenting in south-east Asian and Afro-Caribbean patients. Arising on palms and soles, the lesions may go unnoticed for years and so usually present late, especially on the foot.
Misdiagnosis is common, particularly when pigmentation is absent. They may also occur under the nail, usually that of the thumb or big toe. In this site, the melanin pigment is deposited in the nail, resulting in a longitudinal streak that expands proximally as the melanoma grows in width and the nail grows in length. Late presentation is very typical.
A number of melanomas do not fit into this scheme, including desmoplastic and neurotropic forms, both of which often have no pigment and an atypical appearance resembling scars, or thickened plaques. They are difficult to diagnose, but are very rare.
Types of melanoma
Section 3: Identification of melanoma
In the majority of cases, the identification of melanoma should be a straightforward procedure, but early and atypical lesions will always be a problem, even for the most experienced practitioner.
A good history is essential but close attention should also be paid to the patient's skin type, history of excessive sun exposure and family history.
Ask the patient about the development of any new moles (70 per cent of melanoma arise de novo) and look for changes in their existing moles (top box).
When examining the skin, try to do so in the best light possible. Daylight is preferable. Ask patients to undress, because lesions can be multiple and go unnoticed.
A predisposition to melanoma is a risk factor for other skin tumours, so it is important to examine high-risk sites with care. The draining lymph nodes should also be examined as routine.
Dermoscopy has recently become popular in Australia and Europe. This uses a magnifying lens and light source and is an excellent way of examining moles, although it does take some practice.
A good reference text and an introductory course are essential (see www.dermoscopy.co.uk). The ABCDE rules for clinical signs are also useful (see box).7
Pathology reports for melanoma have become increasingly complicated, in order to aid management and prognosis. As such, they can sometimes seem overwhelming to the occasional observer.
The main things to look for are Breslow thickness (depth in the dermis/subcutis to which a melanoma has spread), melanoma subtype (SSM, LMM, NM, ALM) and the presence of ulceration.
For example, an SSM with Breslow 0.45mm and no ulceration has an excellent prognosis, while an NM with a Breslow of 7mm and ulceration clearly has a poor prognosis.
When a melanoma is suspected, the patient should be referred to secondary care via the two-week wait system wherever possible.
Routine biopsy of suspicious, pigmented lesions in primary care is unwise, because a clinical diagnosis by a dermatologist can often obviate the need for surgery.
Furthermore, inappropriate sampling and tissue handling can make the pathologist's job more difficult than is necessary and can potentially compromise effective clinical management.
How to monitor a mole
Change in existing mole in order of importance:
- Increase in size
- Change in shape
- Change in colour
- Change in outline
- Change in sensation
- Ulceration or bleeding
The abcde criteria
Evolving lesion: changes in size, shape, symptoms (itching, tenderness), surface (especially bleeding) and shades of colour
Section 4: Management of melanoma
The management of melanoma is, on the whole, surgical, because they are generally chemo- and radio-resistant.
Ideally, the lesion should be excised in its entirety down to deep fat, with a 2mm margin. This allows the pathologist to assess for symmetry and offers sufficient material to make a confident assessment.
Wide local excision
Very large lesions may require an incisional biopsy, but punch biopsies are to be avoided. Once the diagnosis is confirmed, there is usually a wide local excision down to fascia.
The margin depends on the Breslow thickness and ranges from 5mm for melanoma in situ to 2cm or more for advanced disease.
Some centres offer sentinel lymph node biopsy. This is a radiological and surgical technique that examines for lymph node involvement and may be helpful in predicting prognosis, but as yet has unproven long-term benefit.
Medical oncologists may be involved with advanced disease.
Melanoma requires regular follow-up, and this is usually between three and five years, depending on Breslow thickness. Other than screening for local recurrence and metastasis, it is worthwhile teaching self-examination, because there is a one in 20 lifetime risk of a new, unrelated melanoma.
We encourage patients to photograph their moles and digital macro pictures are invaluable.
Do use flash to avoid the change in colour balance caused by incandescent light.
Finally, having had a melanoma confers a double risk for melanoma in first-degree relatives, so those self-examination skills should be conveyed to the families too.
- This article was originally published in MIMS Dermatology.
2. MacLennan R, Green A C, McLeod G R, Martin N G. Increasing incidence of cutaneous melanoma in Queensland, Australia. J Natl Cancer Inst 1992; 16; 84(18): 1,427-32.
3. Coory M, Baade P, Aitken J et al. Trends for in situ and invasive melanoma in Queensland, Australia, 1982-2002. Cancer Causes Control 2006; 17(1): 21-7.
4. Kaskel P, Sander S, Kron M et al. Outdoor activities in childhood: a protective factor for cutaneous melanoma? Results of a case-control study in 271 matched pairs. Br J Dermatol 2001; 145(4): 602-9.
5. Staples M P, Elwood M, Burton R C et al. Non-melanoma skin cancer in Australia: the 2002 national survey and trends since 1985. Med J Aust 2006; 184(1): 6-10.
6. Weedon D. Skin Pathology. Churchill Livingstone, 2002 (second edition), pages 821-58.
7. Abbasi N R, Shaw H M, Rigel D S et al. Early diagnosis of cutaneous melanoma: revisiting the ABCD criteria. JAMA 2004; 292(22): 2,771-6.