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Malignant melanoma

Cutaneous malignant melanoma is a malignancy of the epidermal melanocyte which invades into the dermis of the skin.  The incidence of MM is steadily rising. 

There are approximately 10,000 new cases of melanoma in the Uk each year with approximately 2000 deaths.

http://info.cancerresearchuk.org/cancerandresearch/cancers/melanoma/ (accessed 26 June 2012)

Risk Factors

Fair skin with an inability to tan (skin types I and II)
UV radiation = excessive sun exposure
Sunburn
Burning or high sun exposure at a young age
Sunbeds
Atypical or irregular moles
Lots of moles >100 in number
Red hair
Numerous freckles
Family history of melanoma

Remember the ABCD(E) of Melanoma

A asymmetry
B irregular border
C irregular colour
D diameter over 7mm
(E) elevation

Always get a pigmented lesion assessed if there has been rapid or a recent change in size, shape or colour, inflammation, oozing or bleeding or a change in sensation or if the mole is new and there is rapid change

There are 4 main types of melanoma:

1. Lentigo maligna (LM)
2. Superficial spreading (SSMM)
3. Nodular
4. Acral lentiginous (ALMM)

Lentigo maligna (LM) and Lentigo maligna melanoma (LMM)

Lentigo maligna = LM = Hutchinson’s melanotic freckle can be considered to be a precancerous freckle

Lentigo maligna is the premalignant, precancerous or in-situ phase of malignant melanoma. 

LM demonstrates a long growth phase, staying precancerous for years before progressing through peripheral extension until a raised central nodule of full blown cancerous malignant melanoma arises = Lentigo maligna melanoma (LMM).

LM occurs most commonly on the face of the elderly. 

Superficial spreading malignant melanoma (SSMM)

This is the commonest melanoma in fair skinned individuals.

Any site is possible but malignant melanoma commonly affects sun exposed sites such as the back, chest, arms and legs

Men are as likely as women to acquire melanomas on their lower legs.
Women are as likely as men to acquire melanoma on their upper backs

Nodular melanoma

This type of malignant melanoma is a nodule and can arise anywhere on the body. These tend to grow more rapidly than SSMM and can present late when they start to catch on clothing or ulcerate and bleed.

Acral lentiginous melanoma (ALMM)

These occur on acral sites (limbs or extremities) such as the palms, soles and under the nail.

EXAMINATION

Melanomas show
Asymmetry in shape or colour distribution
Irregular Borders
Different Colours
Diameter >7mm
(E)nlargement or (E)levation

Prognosis / survival in malignant melanoma / Breslow thickness

The long term outcome from malignant melanoma depends on its thickness called the Breslow thickness. This is measured microscopically when a pigmented lesion is excised.

It is essential that any suspicious lesions are assessed by a qualified practitioner and treatment undertaken if malignant melanoma is suspected as soon as possible as long-term outcome and prognosis is inversely related to the depth of invasion (=Breslow thickness). An urgent referral to the local dermatology department should be considered.

Having a thick malignant melanoma (Breslow thickness >4mm) results in 5-year survival rates of less than 50%.

Having a thin malignant melanoma (Breslow thickness <1mm) results in 5-year survival rates of more than 95%.

So presenting early with a changing or suspicious mole is vital. Removing a malignant melanoma whilst it is thin can potentially be curative and life-saving.

Approximate 5-year survival

Melanoma In situ 95–100%
<1 mm 95–100%
1–2 mm 80–96%
2.1–4 mm 60–75%
>4 mm 50%

The numbers of thin melanomas is increasing but the numbers of thick melanomas is plateauing or levelling off ie is stable. This means that the mean or average thickness of malignant melanoma drops and results in an averaged improved rate of survival.

(from Mackie RM, Bray CA, Hole DJ et al. Incidence and survival from malignant melanoma in Scotland: an epidemiological study. Lancet 2002; 360: 587-91

Treatment

The only successful treatment is surgical excision.
Excision margins depend on the thickness of the melanoma
1cm for every mm thickness (up to maximum 2cm)

No other therapy has proven survival benefit although many trials are being undertaken.

Metastatic disease is managed with palliative care including surgery and radiotherapy to control symptoms

Staging and management

Staging is based on

Breslow thickness
Lymph nodes
Metastases

Depending on the Breslow thickness, no further tests may be needed.
Investigations may include chest x-ray blood tests, CT scans
Lymph nodes can be biopsied if needed.

Follow up

See revised 2010 MM guidelines

Follow up = 3 monthly for 1 year for MM < 1mm thick

3 monthly for 3 years then 6 monthly for MM >= 1mm thick

Margins

In situ.    

5mm

<1mm. 1cm
1.01-2. 1-2
2.1-4. 2-3
>4mm. 3cm

ABCDE of Melanoma

After treatment

self-examine
take preventative measures
 
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