Melanoma is the 4th most common cancer (excluding non-melanoma skin cancer) in Australia. And Australia has the highest rates of melanoma in the world. In Australia there are about 17000 new melanoma’s diagnosed annually and about 1500 people die every year from metastatic melanoma. Melanoma is commonly treated here at Brisbane City Skin Clinic, by the specialised doctors.
Thankfully, as melanoma’s grow externally on the skin (unlike bowel and breast cancers for example), most of the time they can be easily discovered and treated early before they have the opportunity to spread.
Melanoma’s grow from melanocytes. Melanocytes are specialised types of skin cells that produce a pigment called melanin. Genetically humans produce different amounts of melanin and this determines our skin, hair and eye colour. If these melanocytes are exposed to excessive amounts of radiation damage, mainly due to UV radiation from the sun or tanning beds, then DNA damage occurs and Melanoma can start to grow. Evidence tells us that it is damaging sun exposure during childhood and adolescence that causes the most damage to melanocytes, increasing the risk of melanoma. In addition to this, repeated and regular sun exposure over a long period can cause a different type of melanoma in older Australians.
Most melanomas (around 75%) develop on the skin as a brand new “spot”. In their early stages most of these melanoma appear similar to a mole. But unlike moles, these melanomas grow progressively larger at a rate that can be detected over several month. As the melanoma’s enlarge they begin to display more of their “classic” features. These “classic” features include ASYMMETRIC appearance, BORDER irregularity and COLOUR variation. Most of these melanoma’s will appear as moles that look a bit “unusual” or different to a patients usual moles and will have colours in the tan/brown/black spectrum. It is also important to note that some melanoma’s develop out of a pre-existing mole. That is a mole that a patient has had for many years may suddenly start to grow or change and in some cases this could be a melanoma.
Another important exception is that 10-20% of melanoma’s have little to no brown pigment and can appear as pink or red. Separate to the traditional ABC acronym for melanoma we can use EFG for these less common but very important melanoma’s (Elevated, Firm, Growing).
Types of Melanoma
There are four main types of melanoma:
Superficial Spreading Melanoma
This is by far the most common type and presents usually in the tradition way of a new tan/brown/black lesion that is growing or changing or a pre-existing mole that has suddenly changed. These melanoma’s usually grow “across” the skin for a period of time before growing more deeply and becoming more “invasive”.
Nodular melanoma is a less common but more “aggressive” type of melanoma. These melanoma’s tend to appear more suddenly, be more difficult to notice and are often more deeply invasive for a given diameter. These melanoma tend to have little to initial growth “across” the skin and tend to grow deeply earlier. These melanomas can be brown/black or even pink/red, they can bleed easily or present like a sore that doesn’t heal. They are mostly raised up off the skin.
Acral melanoma is the term given to melanoma’s that grow on the soles of the feet or palms of the hand or in the nails. These are quite rare melanoma’s however there are important to remember and it is important that each time a patients skin is examined for skin cancer that the palms and soles and nails are checked. These melanoma’s mostly present as an enlarging or changing pigmented spot, but occasionally can be non-pigmented.
Lentigo Maligna Melanoma
Lentigo maligna melanoma is a type of melanoma that mostly occurs in older people who have had chronic sun exposure and they tend to grow in areas that have had the most sun exposure such as the face, shoulders, arms and legs. They tend to have a “prolonged” growth phase across the skin, but can become deeply invasive and metastasise.
Some of the risk factors for developing melanoma include:
– Fair skin
– Having a large number of moles
– Red hair and/or light eyecolour
– Having had a previous skin cancer of any type
– Having had a previous melanoma
– Having a family history of melanoma in a 1st relative
The first step in managing a suspected melanoma is to remove the melanoma and send the lesion to the pathologist for analysis. In the majority of cases this will be buy a complete excision and suturing. Occasionally a shave biopsy will be performed instead on selected lesions. Whilst in almost all cases all of the melanoma is removed on this initial procedure the intent of this procedure is not to cure but to confirm the diagnosis of melanoma and to assess the depth of invasion of the melanoma. Once it is known how deep the melanoma has grown then the next procedure can be planned. For example if the melanoma has not invaded into the second layer of skin (called melanoma insitu) then on most occasions the second excision (called a wide local excision) aims to remove 5 mm margin of normal tissue as a safety margin. If however the melanoma has become invasive and is greater than 1 mm deep then on most occasions the second excision will aim to remove 10 mm of normal tissue as a safety margin. In addition, for melanomas that are 1 mm or more deep, a sentinel lymph node biopsy procedure will also be offered.
A sentinel lymph node biopsy is an additional procedure performed at the same time as the wide local excision. This additional procedure aims to identify and remove the first lymph node that drains the size of the melanoma. This lymph node is sent to the pathologist and examined for any deposits of melanoma. If deposits of melanoma are found in this lymph node then further investigations are likely needed and additional treatments can be discussed.