The skin
The skin
- protects us from injury
- cools us when we get too hot
- prevents us from becoming dehydrated.
The skin has two main layers.
Epidermis
The top or outer layer contains three different kinds of cells
- basal cells
- squamous cells
- melanocytes - produce a dark pigment called melanin, the substance that gives skin its colour.
Dermis
The layer underneath the epidermis
- Contains the roots of hairs, glands that make sweat, blood and lymph vessels and nerves.
View image
Skin cancer
Skin cancer develops when a cell in the skin goes through a series of changes that make it a cancer cell. Exposure to ultraviolet (UV) radiation in sunlight is the main factor that causes skin cancer cells to become cancer cells. Skin cancers are named after the type of cell they start from. These are:
- basal cell cancer
- squamous cell cancer
- melanoma.
Melanoma is the least common type of cancer, but it is the most serious type. It can be successfully treated if caught early.
Melanoma
- Melanoma starts from the melanocytes, the cells in the skin that produce melanin, the skin pigment or colour.
- Melanocytes are the cause of freckles and moles on the skin and produce the brown colour of a suntan.
- Melanoma grows quickly. If it is not treated, it may spread to the lower layer of skin, where cancer cells can escape and be carried to other parts of the body or lymph vessels.
Where melanoma occurs
- Anywhere on the skin, even on the soles of the feet.
- In the eye, nervous system and mucous membranes (e.g. lining of the mouth and nasal passages). These types of melanoma are rare.
Types of melanoma
- Superficial spreading melanoma: Grows initially in the top layer of the skin (epidermis). Becomes dangerous when it invades downward into the lower layer of the skin (dermis). Dark brown or black in colour.
- Nodular melanoma: Often very dark brownish black or black in colour but can be pink or red. Forms a raised lump on the surface of the skin as it invades deeper into the skin.
- Acral lentiginous melanoma: Most commonly found on the palms of the hands and soles of the feet or under the nails. More common in people with darker skin.
- Lentigo maligna melanoma: Begins as a large freckle in an area of skin that get a lot of sun exposure, such as the face and upper body. May grow slowly and superficially over many years, later forming lumps as it grows deeper into the skin.
How common is melanoma?
- Australia has the highest rate of skin cancer in the world.
- One in two Australians will develop some form of skin cancer during their lifetime.
- About 3,000 people in NSW are diagnosed with melanoma each year.
Causes of melanoma
The main cause of melanoma is exposure to UV radiation from the sun and other sources, such as tanning machines in solariums.
Each time your unprotected skin is exposed to UV radiation, it changes the structure of the cells and what they do. Overexposure to UV radiation permanently damages the skin and the damage will worsen with more UV radiation.
The most important years for sun protection are during childhood. Exposure to the sun during these years greatly increases the chance of getting melanoma because the damaged cells have much longer to grow and develop into cancer.
Who is most at risk?
- People who are exposed to the sun every now and then (e.g weekends or holidays, not a little bit everyday).
- People who have accumulated a lot of sun exposure in a more continuous pattern.
- People with fair complexions: These people have less skin pigment to protect them against UV radiation from the sun than people with darker skin (e.g. Australian Aborigines and Torres Strait Islanders).
- Older adults: It can also occur in younger adults and occasionally in teenagers. It is rarely seen in children.
- People with a lot of moles: Adults with more than 10 moles on their arms and more than 200 on their body should have their moles checked regularly by their GP.
- People with a family history: If someone in the family has melanoma, there is a two to three times greater chance that other family members may get it.
Signs and symptoms
Melanomas can vary greatly in the way they look. The first sign of a melanoma is usually a change in an existing freckle or mole or the appearance of a new spot. The change may be in:
- Colour: blotchy with a wide variety of colours, such as brown, black, blue, red, white and/or light grey.
- Size: begins to, or keeps getting, larger.
- Shape: irregular edge (scalloped or notched). If a line was drawn through the middle of the melanoma, the two sides would not match up. It may increase in height or become scaly.
Changes are normally noticed over several weeks or months rather than days. A freckle or mole that bleeds or itches can suggest a change.
It is normal for new moles to appear and change during childhood and pregnancy. However, in adults a new mole could be a melanoma. Talk to your doctor about any changes.
Melanoma can occur anywhere on the body, but mainly develops in areas that are usually or occasionally exposed to the sun when a person is outdoors.
For men, melanoma is more common on the back. Women get more melanomas on their legs than men.
View images of early, moderate, and advanced melanomas.
How a diagnosis starts
The suspicious spot or mole, and all other moles, are examined.
The doctor will feel the nearby lymph nodes and ask about your history, and your family's history, of melanoma.
Biopsy
- A quick and simple procedure to remove the suspected spot.
- Your GP, or a dermatologist or surgeon, does the biopsy.
- A local anaesthetic is used.
- The spot and some surrounding tissue is cut out with a scalpel. You will have a stitch or two to close up the area where the mole has been cut out.
- The tissue is sent to a laboratory for examination under a microscope.
- Usually takes at least a week for the results of your tests to be ready, and a follow-up appointment may be arranged.
- If the cells are found to be cancerous, the doctor may do some other tests to see if the cancer cells have spread.
Staging the melanoma
Staging means the doctor determines:
- the extent of the spread of the disease
- if the melanoma has moved to the lymph nodes or through the bloodstream into the internal organs.
Staging is done in two steps:
- Measuring the depth (thickness) of a melanoma.
- Detecting the tumour elsewhere in the body.
Measuring the depth (thickness) of a melanoma
The depth of the melanoma is important because the deeper the cancer cells have grown into the skin, the more likely it is the cancer will come back (recur) or spread to the lymph nodes or internal organs.
If the cancerous cells are only in the uppermost skin, and have not penetrated into deeper tissues, this is called a tumour in-situ. In some cases, biopsy may be all the treatment that is needed.
If the tumour has penetrated further into the skin, more tissue and skin may need to be removed from around the melanoma.
How the depth of a melanoma is measured
Pathologists examine the biopsy and measure the depth of the melanoma. This is called the Breslow thickness. Melanomas are classified as:
- Thin: 1mm or less
- Intermediate: 1 – 4mm
- Thick: more than 4mm.
As the tumour becomes deeper, the risk for recurrence becomes higher. Once tumours are deeper than 4 mm, the risk for recurrence is more than 50 per cent. Your pathology report may also give the Clark level (1 - 5), which is based on the layer of skin the melanoma has invaded.
Both measurements are used when determining the overall staging of the melanoma.
Detecting the tumour elsewhere in the body
The doctor will examine the lymph nodes closest to the melanoma. For thin melanomas, this will usually be the only extra test that the doctor does.
If the doctor feels a lump in the lymph nodes, they will insert a needle into the lymph node to remove some cells for the pathologist to examine. This is called a needle biopsy.
Tests may also be done to look for cancer in the internal organs. These tests are only needed if the melanoma is very deep, i.e. greater than 4 mm deep.
More than half the invasive melanomas diagnosed in NSW are less than 1 mm thick.
Staging tests
Some tests for staging a melanoma are:
Sentinel node biopsy
- A technique to see if the melanoma has spread to the lymph nodes closest to the melanoma.
- Sentinel node is the lymph node that has the closest connection to the melanoma (e.g. it is the node it drains to first)
- Substance containing a small amount of radioactivity is injected into the skin around the tumour, and it is passed into the sentinel node.
- The sentinel node can be removed and examined to see if there are any cancer cells in it.
- Only used for deeper melanomas.
CT scan
A series of detailed pictures of areas inside the body taken from different angles. The pictures are created by a computer linked to an x-ray machine. Also called CAT scan, computed tomography scan, computerised axial tomography scan, and computerised tomography.
MRI
A procedure in which radio waves and a powerful magnet linked to a computer are used to create detailed pictures of areas inside the body. These pictures can show the difference between normal and diseased tissue. MRI makes better images of organs and soft tissue than other scanning techniques, such as computed tomography (CT) or x-ray. MRI is especially useful for imaging the brain, the spine, the soft tissue of joints, and the inside of bones. Also called magnetic resonance imaging, NMRI, and nuclear magnetic resonance imaging.
PET Scan
- Not necessary in thinner melanomas because there is a very low risk that the cancer has spread to internal organs. Even when tumours are more than 4 mm deep, the internal spread, if it is present, is likely to be too small to be detected by scans.
- Used for deeper tumours.
- Can be repeated at a later stage if symptoms develop that suggest the tumour may have spread to an internal organ.
Prognosis
More than 85% of people with melanoma are cured by surgery. With early detection and treatment, the percentage of people cured has grown steadily over the past 20 years. Prognosis means the expected outcome of a disease. Factors influencing prognosis include:
Early diagnosis
- Melanoma can be treated most effectively in its early stages, when it is still confined to the outer layer of the skin.
- The deeper a melanoma penetrates into the skin, the greater the risk that it may spread to draining lymph nodes or to other body organs.
Gender
- Women seem to do better than men, but it is unclear why this is so.
- Aspects of a melanoma's appearance under the microscope, other than its thickness, may predict a better or a worse outcome.
You need to talk to your doctor about your prognosis. Only someone who knows your medical history can tell you what to expect and the treatment options that are best for you.
Treatment
The treatment options available include:
- Surgery
- Radiotherapy
- Chemotherapy
- Palliative care
You may have one of these treatments or a combination. Your doctor will advise you on the best treatment for you. This will depend on the stage of the melanoma and what you want.
Which health professionals will I see?
Health professionals who care for people with melanoma include:
- Dermatologists — specialise in skin disorders
- Surgeons — specialise in surgery
- Plastic surgeons — specialise in surgery of the skin
- Medical oncologists — responsible for chemotherapy
- Radiation oncologists — responsible for radiotherapy
- Nurses — assist you through all stages of your hospitalisation and cancer experience
- Social workers, physiotherapists and occupational therapists — advise you on support services available and help you resume normal activities.
Most people with melanoma will only need to have the melanoma removed. They will not need to see a medical oncologist or a radiation oncologist or even be admitted to hospital.