Malignant Melanoma (MM)

What is Malignant Melanoma (MM)?

Malignant Melanoma is a potentially fatal malignancy of the epidermal melanocyte which invades into the dermis of the skin. The incidence of MM is steadily rising. There are approximately 10,672 new cases of malignant melanoma diagnosed each year.
http://info.cancerresearchuk.org/cancerstats/types/skin/   [accessed March 2010]

Remember the ABCD of Melanoma

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

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 and or Numerous freckles
• Family history of melanoma

There are 4 main types of melanoma:

• Lentigo maligna [LM]
• Superficial spreading [SSMM]
• Nodular
• 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, then it turns into 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 the following typical characteristics:

• Asymmetry in shape or colour distribution
• Borders that are irregular
• Colour that is different in patches
• Diameter greater than 7mm
• Enlargement or elevation

Prognosis /survival in malignant melanoma

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 related to the depth of invasion (or Breslow thickness).

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

The numbers of thin melanomas is increasing but the numbers of thick melanomas is plateauing or leveling off, i.e. more 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

For more information on treatments for skin cancers in general click here

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 and Lymph nodes can be biopsied if needed.

Management:

Follow up is usually 3-monthly for 3 years if Breslow thickness was < 1mm
If >1mm then additional 6-monthly follow-up for a further 2 years 
[From Roberts DLL, Anstey AV, Barlow RJ et al. UK guidelines for the management of cutaneous melanoma. Br J Dermatol 2002; 146: 7-17]

After treatment self-examine regularly and take preventative measures against risk factors.

Location of Malignant Melanoma

Studies have suggested that males were as likely as females to acquire melanomas on their lower legs Females were as likely as males to acquire melanoma on their upper backs. This suggests similar levels of UV exposure for both sexes in current times.

Previously, it was found in a study [1972-1977] that men had more malignant melanoma on their trunk, especially their back and women more MM on their face and lower legs and other studies confirmed this [see ref 2 in Clark, Shin et al]

Reference : Clark LN, Shin DB, Troxel AB et al. Association between the anatomic distribution of melanoma and sex. J Am Acad Dermatol 2007; 56: 768-73] 

Melanoma in Organ Transplant Recipients(OTRs)

Melanoma accounts for 6.2% of all transplant skin cancers in adults
Melanoma accounts for 15% of all transplant skin cancers in children

3-4 fold increase in melanoma incidence in transplant recipients compared to age and gender matched controls

Melanoma in OTR is more likely to be associated with precursor naevus [50-70%] compared to controls [20%]

Reference: Fluchiero GJ, Wood LD, Miller JJ. Sudden onset of brown macules.J Am Acad Dermatol 2007; 56(5) 898-9:

A good website that looks at how to cope with the diagnosis of melanoma and further information for people with a family history of melanoma is www.genomel.org