Last updated: June 2024
What is melanoma?
Melanoma is a cancer that arises in pigment cells of the skin (melanocytes). If not detected early, it has the capacity to spread through blood vessels and lymph channels to other parts of the body.
Australia has some of the highest rates of melanoma in the world, with more than 18,000 cases diagnosed each year. 1
Who gets melanoma?
Melanomas are more common in individuals with fair skin. Individuals with large numbers of moles or large, unevenly coloured, irregularly shaped (dysplastic) moles are more likely to develop a melanoma. Light hair (especially red hair) and light eye colour are associated with a greater risk of developing melanoma. Other risk factors include freckles (a marker of fair skin) and solar lentigines (sunburn freckles).
Individuals with a family history of melanoma have a 74% increased risk in developing melanoma. 2
Individuals who have had a previous skin cancer diagnosis are at increased risk of developing melanoma. Individuals who have also had at least one melanoma are at high risk of developing a new melanoma.
What causes melanoma?
Almost all melanomas are caused by exposure to ultraviolet (UV) radiation from the sun or solariums.
Most melanomas in younger Australians (under 50 years) are due to occasional sun exposure of the kind that produces sunburn. Childhood sun exposure is a particularly important contributor to these melanomas. Melanomas in older Australians (over 50 years) are more strongly related to regular sun exposure over a long period.
What does melanoma look like?
More than half of melanomas begin as a new spot and the remainder, arise from a pre-existing mole. 3 They begin as a flat, light brown to black spot that looks like a mole. However, melanomas, unlike moles, will grow progressively larger at a rate that will often be detected over a few months. As they enlarge, changes in shape and colour also progress so that the spot becomes increasingly irregular in shape or variable in colour.
An important exception is the melanomas that have little or no pigment and appear predominantly red in colour.
Another exception is nodular melanoma, which has no flat phase and presents as raised from the outset and are also most often red in colour. These may bleed repeatedly especially if they are knocked or bumped.
Melanomas that are detected while they are still flat are almost always cured by removal. All melanomas will eventually become raised, increase in-depth and become more life threatening.
Figure 1. Initially flat melanoma (superficial spreading type) – Image reproduced with permission of Prof John Kelly
Figure 2. Initially flat melanoma (superficial spreading type) – Image reproduced with permission of Prof John Kelly
Figure 3. Initially flat melanoma (superficial spreading type) with little pigmentation (hypomelanotic or amelanotic) – Image reproduced with permission of Prof John Kelly
Figure 4. Initially raised (nodular) melanoma. These usually have little pigment – Image reproduced with permission of Prof John Kelly
Figure 5. Initially raised (nodular) melanoma. These usually have little pigment – Image reproduced with permission of Prof John Kelly
How is melanoma diagnosed?
If an individual has a suspicious spot, they should consult their GP. Following initial examination, they may then be referred to a dermatologist for further assessment.
If possible, suspicious spots are removed completely and the entire spot sent to pathology for assessment. Partial biopsies are sometimes necessary.
How is melanoma treated?
Treatment options will vary depending on the individual and their needs.
All melanomas are treated surgically by removing both the melanoma along with a safety margin of normal appearing skin around it. The width of the safety margin removed varies according to the depth of the melanoma.
If the melanoma is more than 0.8 mm in depth, there may be the option of a sentinel node biopsy (SNB).
A SNB may provide information about an individual’s risk for spread of melanoma beyond the skin. For individuals with both a higher risk of primary melanoma and a positive SNB, the addition of targeted or immunotherapy will offer a reduced chance of recurrence.
Treatment with drugs targeting specific melanoma mutations (targeted therapy) or immunotherapy may reduce recurrence after initial melanoma spread has been treated. These drugs are also used to treat advanced spread that cannot be surgically removed.
What is the likely outcome of melanoma?
Melanomas that are diagnosed early often have a good prognosis (very low risk of spreading to other body parts or becoming life threatening).
Once it begins to grow in depth, the prognosis of melanoma differs, depending on several factors.
The depth of the melanoma (thickness), ulceration (surface breakdown and crusting) and the stage of melanoma (how advanced and how far spread it already is) can influence an individual’s risk of the spread from melanoma.
- Australian Institute of Health and Welfare 2023. Cancer data in Australia. Canberra: AIHW. Available from: https://www.aihw.gov.au/reports/cancer/cancer-data-in-australia/contents/cancer-mortality-by-age-visualisation
- Wei EX, Li X, Nan H. Having a first-degree relative with melanoma increases lifetime risk of melanoma, squamous cell carcinoma, and basal cell carcinoma. J Am Acad Dermatol. 2019 Aug;81(2):489-499. doi: 10.1016/j.jaad.2019.04.044. Epub 2019 Jun 21. PMID: 31230976.
- Bhatt M, Nabatian A, Kriegel D, Khorasani H. Does an increased number of moles correlate to a higher risk of melanoma? Melanoma Manag. 2016 Jun;3(2):85-87. doi: 10.2217/mmt-2016-0001. Epub 2016 May 19. PMID: 30190875; PMCID: PMC6096442.
| Prof John Kelly | June 2024 |
| Prof John Kelly | October 2022 |