Skin cancer is an alarmingly common problem in New Zealand and we have one of the highest skin cancer rates in the world.
The most common skin cancers are BCC (basal cell carcinoma), SCC (squamous cell carcinoma) and melanoma. The most common pre-cancerous skin cancer is actinic keratosis. Early diagnosis and treatment can prevent SCC and melanoma from spreading to other parts of the body. A full body skin check including dermoscopy is the best way to detect early pre-cancerous and cancerous skin lesions. A mole map is also performed when serial photography is needed. Skin cancer treatments involve biopsy and adequate skin excision which is performed by doctors at Palm Clinic.
Moles are common skin growths which are usually benign but can sometimes undergo change to become a malignant melanoma. The medical term for moles is melanocytic naevi as they are due to a proliferation of the pigment cells (melanocytes). If they are brown or black in colour they may also be called pigmented naevi. Moles are benign in nature, but a malignant melanoma (cancerous mole) may start within a benign mole.
Moles may be flat or protruding from the skin. They vary in colour from pink or flesh tones to dark brown or black. Although mostly round or oval in shape, they are sometimes unusual shapes and range in size from a couple of millimetres to several centimetres in diameter. The number of moles a person has depends on genetic factors and on sun exposure; most Pakeha New Zealanders have 20-50 of them. People with a greater number of moles have a higher risk of developing melanoma than those with just a few moles, especially if they have over 100 of them.
When do moles first appear?
One or more moles may be present at birth. These brown birthmarks are known medically as congenital melanocytic naevi. Other birthmark like moles can appear within the first two years of life.
More frequently moles arise during childhood or early adult life, when they are called acquired melanocytic naevi. Exposure to sunlight increases the number of moles. Teenagers and young adults tend to have the greatest number of moles and there are fewer in later life because some of the moles fade away over time.
Classification of moles
The conventional classification of melanocytic naevi depends on their appearance under a microscope . They are described according to the site of the naevus (mole) cells in the skin.
- Junctional naevi Junctional naevi have groups or nests of naevus cells at the junction of the epidermis (outer layer of the skin) and the dermis (inner layer). These tend to be flat colourful moles.
- Dermal naevi Dermal or intradermal naevi have naevus cell nests in the dermis. These moles are thickened and often protrude from the skin surface. They may be pigmented or skin-coloured.
- Compound naevi Compound naevi have nests of naevus cells at the epidermal-dermal junction as well as within the dermis. These moles have a central raised area and may be surrounded by flat pigmentation.
A new classification of moles relies on their appearance on dermoscopy, a technique used by doctors to evaluate the structure of moles using a hand-held magnification device. Dermoscopic patterns of melanocytic naevi include:
- Reticular naevi
- Globular naevi
- Blue naevi
- Starburst naevi
- Site-related naevi
- Naevi with special features
- Unclassifiable naevi
The best way to monitor moles, particularly if you are in a high risk group is to have a full body skin check including a special diagnostic intrument called dermoscopy. Mole map is not as useful as this is just serial photography but moles of concern will be mapped for comparison ifthey do not requireimmediate punch biopsy or excision. At Palm Clinic Dr Martin Denby offers full body skin checks with dermoscopy. If he is concerned that you may have a type of skin cancer depending on the size and site of the lesion he can perform a punch biopsy and surgical excision at Palm Clinic. Benign moles can be removed for cosmetic reasons using Surgitron radifrequency which is less likely to leave a scar than a surgical excision.
Mole "checks" are not covered by Southern Cross but if you have a melanoma or other type of skin cancer the consultation and biopsy or skin lesion excision would be covered by your insurance.
Malignant melanoma is a potentially serious type of skin cancer. This needs to be diagnosed and treated early to improve survival rates. Depending on the size and site of the melanoma you may be offered a wide excision and biopsy of the suspected melanoma at Palm Clinic or referral to a plastic surgeon.
Frequently Asked Questions About Melanoma
Who is at risk of melanoma?
Melanoma is most common in pale skinned people, but it may rarely develop in those with dark skin as well. About one in fifteen Pakeha New Zealanders are expected to develop melanoma in their lifetime – New Zealand and Australia have the highest reported rates of melanoma in the world. Melanoma is the third most common cancer in New Zealand females and the fourth most common cancer for males.
Melanoma can occur in adults of any age but is very rare in children. New Zealand statistics in 2003 showed:
- Fewer than 1% occurred under 20 years old
- 13% occurred at 20 to 40 years old
- 36% aged 40 to 59 years old
- 51% over 60 years old
Unfortunately, about 15% of those with invasive melanoma die from it; around 250 New Zealanders die from melanoma each year. The main risk factors for developing melanoma are:
- Fair skin that burns easily
- Blistering sunburn especially when young
- Previous melanoma
- Previous non-melanoma skin cancer (BCC/SCC)
- Family history of melanoma, especially if two or more members are affected
- Large numbers of moles (especially if there are more than 100)
- Abnormal moles –dysplastic naevi syndrome
How does a melanoma grow?
Where on the body do melanomas grow?
Melanoma can arise from normal appearing skin (50% of melanomas) or from within a mole or freckle, which starts to grow larger and change in appearance. Precursor lesions include:
- Congenital melanocytic naevus (brown birthmark)
- Atypical or dysplastic naevus ( multiple irregular variegated coloured moles)
- Benign melanocytic naevus (normal mole)
Melanomas can occur anywhere on the body, not only in areas that get a lot of sun. The most common site for men is the back (around 40% of melanomas), and the most common site for women is the leg (also around 40%).
Although melanoma usually starts as a skin lesion, it can also grow on mucous membranes such as the lips or genitals. Occasionally it occurs in other parts of the body such as the eye, brain, mouth or vagina.
What do melanomas look like?
The first sign of a melanoma is usually a changed or new freckle or mole. It may have an unusual shape. A melanoma may be detected at an early stage when it is only a few millimetres in diameter, but they may grow to several centimetres in diameter.
It may have a variety of colours including tan, dark brown, black, blue, red and, occasionally, light grey. Melanomas that are lacking pigment are called amelanotic melanoma. During the horizontal growth phase, a melanoma is normally flat. As the vertical phase develops, the melanoma becomes thickened and raised.
Some melanomas are itchy or tender. More advanced lesions may bleed easily or crust over. Any mole with the following characteristics should be checked by a doctor immediately:
- Border is uneven
- Colour variation
- Diameter greater than 6mm
- Evolving – any change in size, shape colour or new symptoms such as bleeding, itching crusting
An actinic keratosis is a scaly lump that forms on sun exposed skin surfaces. Actinic keratosis is also called AK, solar keratosis or sun spots. They are generally the same colour as the skin but can become pigmented. The scale or crust is dry, and rough, and often is noticed by touch rather than sight. Actinic keratosis may disappear when the crust falls off or is picked off but will usually reappear until treated. About half will go away on their own if you avoid sun for a few years. AK’s generally appear on sun exposed areas like the face, ears, backs of hands, scalp, neck, forearms, and lips.
Actinic keratosis can be a precursor to skin cancer. About 10 to 15 percent of active AK’s, which are more tender and redder than the rest will progress to SCC (squamous cell carcinoma). The most aggressive form of AK, actinic cheilitis, appears on the lips and can evolve into SCC. When this happens, about 20% of these skin cancers spread to other parts of the body. People with actinic keratosis are more likely to develop melanoma also. Sun exposure is the cause of almost all actinic keratoses. It is lifetime sun exposure, not recent sun-tanning that adds to your risk. Up to 80% of sun damage is thought to occur before the age of 18. UV rays bounce off reflective surfaces like sea and snow; about 80% can pass through clouds. The thinning of the ozone layer may be allowing more ultraviolet rays reach the earth. People who have fair skin, blonde or red hair, blue, green, or grey eyes are at the greatest risk. Because their skin has less protective pigment, they are the most susceptible to sunburn. Even darker-skinned people can develop actinic keratosis if they have lots of sun exposure.
How is actinic keratosis treated?
There are a number of effective treatments for removing actinic keratoses. The decision on whether and how to treat is based on the nature of the lesion, your age, and health but large, multiple or inflamed Actinic keratoses need to be treated to prevent change to a skin cancer.
- Liquid nitrogen, one of the most common treatments, freezes off lesions through cryosurgery. Longer freezes can result in hypopigmented (white) areas.
- Surgitron curettage is another treatment. The doctor scrapes the lesion and may take a biposy specimen to be tested for cancer.
- Shave Removal uses a scalpel to shave the AK and obtain a specimen for testing. The base of the lesion is destroyed, and the bleeding is stopped by cauterizing.
- Chemical peels make use of acid applied all over the area. The top layers of the skin peel off and are usually replaced within seven days by growth of new skin. Redness and soreness usually disappear after a few days.
- Fraxel Dual is a fractional resurfacing laser which produces results similar to a chemical peel but is less likely to cause side effects.
- Topical creams like Aldara are effective in treating keratoses, particularly when lesions are numerous. Aldara works by stimulating the body's immunity to recognize the AK’s and treat them. This is used twice weekly for 6-12 weeks over the affected areas. 5-fluorouracil (Efudix) cream works by directly attacking the precancerous cells directly. This is applied once to twice daily for 2 to 4 weeks. Treatment leaves the affected area temporarily red and raw and will cause some discomfort. The more raw and inflamed the skin becomes, the better the end result.
Regular follow-up visits are usually needed when there are many keratoses.
The most common types of skin cancer in New Zealand are Basal Cell Carcinoma and Squamous Cell Carcinoma.
Basal Cell Carcinoma (BCC)
Basal cell carcinoma (BCC) or rodent ulcer is the most common type of skin cancer and is particularly common in New Zealand because of issues with the ozone layer. Fortunately this form of skin cancer is very rarely a threat to life. BCC are classified as nodular, superficial, morphoeic or pigmented.
BCC typically affects adults of fair complexion who have had a lot of sun exposure, or repeated episodes of sunburn and they are more common in the elderly.
Squamous Cell Carcinoma (SCC)
Squamous cell carcinoma (SCC) is a common type of skin cancer. It is derived from squamous cells, the cells that make up the outside layers of the skin (epidermis). These cells produce keratin, the horny protein that makes up skin, hair and nails. Invasive SCC refers to skin cancer cells that have grown into the deeper layers of the skin (dermis). Invasive SCCs are usually slowly-growing, tender, scaly lumps. They may develop sores or ulcers that fail to heal.
Most SCCs are found on sun-exposed sites, particularly the face, lips, ears, scalp, hands, forearms and lower legs. They vary in size from a few millimetres to several centimetres in diameter. Sometimes they grow to the size of a pea or larger in a few weeks, though more commonly they grow slowly over months or years.
What do I do if I think I have a BCC or SCC?
You cannot expect to make the diagnosis yourself so we recommend you book an appointment with Dr Martin Denby and Dr John Barrett who have a special interest in skin cancer. They will perform a full body skin check and if you have a BCC or SCC they can arrange for a biopsy and full excision.
Palm Clinic is an Affiliated Provider to Southern Cross Health Society for skin cancer treatment, skin biopsies, and skin cancer surgery. Medical necessity criteria apply.