Malignant
Melanoma
Definition
Malignant melanoma is a skin cancer due to cancerous changes
in skin pigment cells (melanocytes).
Incidence/Age/Sex
The incidence of melanoma is about 10 per 100,000 per year
in the UK. Melanoma is very rare in children (<0.3%);
thereafter the incidence increases steadily with age. In
the UK females are more often affected than males (about
1.5 times more common).
Causes/Preventions
Exposure to sunlight is associated with melanoma. Pattern
of exposure is important - intermittent, intense exposure
being more important than chronic exposure. Childhood sunburn
associated with five times increased risk. Sun-beds deliver
mainly UVA to the skin and this may be a risk factor. Other
risk factors: fair-skin; > 50 moles; positive family
history; previous history of melanoma and certain inherited
conditions.
Symptoms & Signs
A melanoma may arise from clear skin or a pre-existing mole;
it can occasionally arise at unusual sites such as under
a nail or inside the mouth. Suspicious early symptoms include:
change in size, shape or colour of a lesion. These changes
typically occur over a few months. Other, later, symptoms
include change in surface characteristics, inflammation,
crusting, ulceration, itching or bleeding. Pain is unusual
except in very advanced disease. Melanomas are typically
irregular and pigmented lesions of the skin. They may be
a raised lump (nodular type) or flat and spreading (superficial
spreading type) or a combination of these appearances.
Signs of Melanoma
A = Asymmetry (The lesion is asymmetric if opposite segments
are different)
B = Border (The border of a melanoma is usually irregular,
with notches and prominences around the edge. Some or all
of the edge is well defined)
C = Colour - Changing colour - getting darker or becoming
patchy and/or a reddish margin
D = Diameter (Diameter greater than 7mm or the top of a
pencil is a feature of most melanomas)
E = Elevation (Elevation of its surface may be present.
Elevation implies an advanced melanoma).
Complications
of Disorder
Melanoma may spread to lymph glands and around the body;
it is a potentially fatal condition. About 30% of patients
develop lymph gland disease; 25% eventually die of their
disease. The likelihood of a melanoma spreading depends
on its thickness measured under a microscope. Thinnest melanomas
have the best chance for complete cure (see outcome). Early
detection is therefore very important.
Tests
The diagnosis of melanoma can only be confirmed by a biopsy.
This should involve cutting out all of the suspicious lesion
(an excision biopsy). Special tests are necessary if spread
is suspected.
Treatment
Surgical
Definitive treatment - an operation known as wide local
excision (WLE) should follow the biopsy. This involves cutting
out an additional skin and underlying fat around the excision
biopsy scar. WLE should not be performed until the thickness
of the melanoma is known. With increasing thickness more
skin, up to a maximum of 3cm around the scar, needs to be
cut out. After WLE the wound may be repaired by stitching
or may need a skin graft or skin flap to repair.
If melanoma spreads to the lymph glands - a painless, firm
lump in the lymph nodes near the original melanoma will
be found. The areas where this may happen are the groins,
arm-pits and neck. The treatment for this problem is surgical
removal of the lymph nodes (lymph node dissection).
If melanoma spreads elsewhere around the body - surgery
may rarely be helpful in relieving unpleasant symptoms,
but is not generally a curative procedure.
Medical
Curative
The risk of relapse of malignant melanoma depends on several
factors including the stage (whether it has spread to the
lymph nodes or other organs), the depth within the skin
it has invaded and the site it has arisen on. In addition,
there are characteristics seen on microscopic examination
of the melanoma which may indicate a higher risk of relapse.
Surgery remains the best treatment for cure. There have
been randomised trials of preventative (adjuvant) treatment
of chemotherapy following surgery in high risk patients
which have shown no improvement in survival. One trial of
interferon for 1 year has shown a moderate survival benefit
but this result is yet to be confirmed in subsequent trials.
The side-effects of interferon treatment includes flu-like
symptoms, lethargy, fevers and therefore compliance with
treatment for this duration is a problem.
Palliative
If the melanoma has spread to other organs (such as liver,
lungs, brain or bone) and surgery is not possible, treatment
is aimed at relieving symptoms rather than cure. Chemotherapy
is sometimes used but on the whole, response rates to this
form of treatment is poor (10-20%) and toxicity (such as
nausea and vomiting, low blood count, hair loss) can be
significant. There is no evidence that chemotherapy improves
survival in advanced disease. If the problem is within a
limb, isolated limb perfusion or intra-arterial chemotherapy
may give better palliation. Specific localised problems
may be treated by radiotherapy (such as painful lump or
bone) with good response rates. In malignant melanoma, many
experimental therapies with tumour vaccines, gene therapy
and other forms of biological treatment are being investigated
and their benefits remain uncertain until further results
become available.
Outcome
The primary determinant of survival following a diagnosis
of melanoma is the thickness of the tumour measured after
the excision biopsy (Breslow thickness). Breslow thickness
can be used to predict survival rates for populations of
patients with melanoma.
