This article explains the symptoms of melanoma, how it is diagnosed, and how it is treated. We also explain how best to prevent melanoma.
What is melanoma?
The most common cause of melanoma is excessive sun exposure.
Melanoma is a form of skin cancer that arises when pigment-producing cells—known as melanocytes—mutate and become cancerous.
Most pigment cells are found in the skin, but melanoma can also occur in the eyes (ocular melanoma) and other parts of the body, including, rarely, the intestines. It is rare in people with darker skin.
Melanoma is just one type of skin cancer. It is less common than basal cell and squamous cell skin cancers, but it can be dangerous because it is more likely to spread, or metastasize.
Melanomas can develop anywhere on the skin, but certain areas are more prone than others. In men, it is most likely to affect the chest and the back. In women, the legs are the most common site. Other common sites are the neck and face.
According to the National Cancer Institute, about 87,110 new melanomas were expected to be diagnosed in 2017, and about 9,730 people were expected to die of melanoma.
The stage at which a cancer is diagnosed will indicate how far it has already spread and what kind of treatment is suitable.
One method of staging melanoma describes the cancer in five stages, from 0 to 4.
Stage 0: The cancer is only in the outermost layer of skin and is known as melanoma in situ.
Stage 1: The cancer is up to 2 millimeters (mm) thick. It has not spread to lymph nodes or other sites, and it may or may not be ulcerated.
Stage 2: The cancer is at least 1.01 mm thick and it may be thicker than 4 mm. It may or may not be ulcerated, and it has not yet spread to lymph nodes or other sites.
Stage 3: The cancer has spread to one or more lymph nodes or nearby lymphatic channels, but not to distant sites. The original cancer may no longer be visible. If it is visible, it may be thicker than 4 mm, and it may also be ulcerated.
Stage 4: The cancer has spread to distant lymph nodes or organs, such as the brain, lungs, or liver.
There are four types of melanoma.
Superficial spreading melanoma: This is the most common, and it often appears on the trunk or limbs. The cells tend to grow slowly at first, before spreading across the surface of the skin.
Nodular melanoma: It is the second most common type, appearing on the trunk, head, or neck. It tends to grow more quickly than other types, turning red—rather than black—as it grows.
Lentigo maligna melanoma: This is less common, and tends to affect older people, especially in parts of the body that have been exposed to the sun over several years. It starts as a Hutchinson's freckle, or lentigo maligna, which looks like a stain on the skin. It usually grows slowly and it less dangerous than other types.
Acral lentiginous melanoma: This is the rarest kind of melanoma. It usually appears on the palms of the hands, soles of the feet, or under the nails. It is more likely in people with darker skin and does not appear to be linked to sun exposure.
As with all cancers, research is ongoing into the causes of melanoma.
People with certain types of skin are more prone to developing melanoma, and the following factors are associated with an increased incidence of skin cancer:
- high freckle density or tendency to develop freckles after sun exposure
- high number of moles
- five or more atypical moles
- presence of actinic lentigines, small gray-brown spots, also known as liver spots, sun spots, or age spots
- giant congenital melanocytic nevus, brown skin marks that present at birth, also called birth marks
- pale skin that does not tan easily and burns, plus light-colored eyes
- red or light-colored hair
- high sun exposure, particularly if it produces blistering sunburn, and especially if sun exposure is intermittent rather than regular
- age, as risk increases with age
- family or personal history of melanoma
- having an organ transplant
Of these, only high sun exposure and sunburn are avoidable.
The World Health Organization (WHO) estimates that around 60,000 early deaths occur each year worldwide because of excessive exposure to the sun's ultraviolet (UV) radiation. An estimated 48,000 of these deaths are from malignant melanoma.
Avoiding overexposure to the sun and preventing sunburn can significantly lower the risk of skin cancer. Tanning beds are also a source of damaging UV rays.
If you can tell the difference between a normal mole or freckle and skin cancer, it may help get an early diagnosis.
There are different types of melanoma skin cancer.
Superficial spreading melanoma
Image credit: National Cancer Institute
Image credit 0x6adb015, own work, 2011
Lentigo maligna melanoma
Acral lentiginous melanoma
Image credit Will Blake, 2006,
Skin changes due to cancer
As with other forms of cancer, the early stages of melanoma may be hard to detect, so it is important to check the skin actively for signs of change.
Alterations in the appearance of the skin are key indicators of melanoma and are used in the diagnostic process.
The Melanoma Research Foundation has produced a web page that compares pictures of melanoma with those of normal moles.
This American non-profit organization also lists the symptoms and signs that should prompt a visit to the doctor.
- skin changes, such as a new spot or mole or a change in color, shape, or size of a current spot or mole
- a skin sore that fails to heal
- a spot or sore that becomes painful, itchy, or tender, or which bleeds
- a spot or lump that looks shiny, waxy, smooth, or pale.
- a firm red lump that bleeds or appears ulcerated or crusty
- a flat, red spot that is rough, dry, or scaly
The ABCDE examination of skin moles is also a key way to reveal suspect lesions. It describes five simple characteristics to look out for in melanoma appearance:
Asymmetric: normal moles are often round and symmetrical, whereas one side of a cancerous mole is likely to look different from the other side - not round or symmetrical.
Border: this is likely to be irregular rather than smooth - ragged, notched, or blurred.
Color: melanomas tend not to be of one color but to contain uneven shades and colors, including varying black, brown, and tan, and even white or blue pigmentation.
Diameter: a change in the size of the mole, or a mole that is larger than a normal mole (more than a quarter inch in diameter) can indicate skin cancer.
Evolving: a change in a mole's appearance over a period of weeks or months can be a sign of skin cancer.
The treatment of skin cancer is similar to that of other cancers, but, unlike many internal cancers, it is easier to access the cancer to remove it completely. Surgery is the most common treatment for melanoma.
Surgery involves removing the lesion and some of the normal tissue around it. A biopsy may be taken at the same time.
If melanoma covers a large area of skin, a skin graft may be necessary. If the cancer may have penetrated into the lymph nodes, a lymph node biopsy may be performed.
Other, less common treatments for skin cancer include:
- biological therapy, using drugs that work with the immune system
Rarely, photodynamic therapy, which uses a combination of light and drugs, and radiation are used.
Avoiding excessive exposure to UV radiation reduces the risk of melanoma.
Avoiding excessive exposure to ultraviolet radiation can reduce the risk of skin cancer.
This can be achieved by:
- avoiding sunburn
- wearing clothes that protect against the sun
- using sunscreen with a minimum sun protection factor (SPF) of 15, but preferably SPF 20-30, with 4- or 5-star UVA protection
- liberally applying sunscreen about half an hour before going out, and applying it again after half an hour
- reapplying every 2 hours and after swimming to maintain adequate protection
- avoiding the highest sun intensity between 11 am and 3 pm by finding shade.
- protecting children by keeping them in the shade, with clothing, and by applying SPF 50+ sunscreen
- keeping infants out of direct sunlight
Wearing sunscreen is not a reason to spend longer in the sun. Sun exposure should still be limited, where possible. People who work outdoors should take precautions to minimize exposure.
Doctors recommend avoiding tanning booths, lamps, and sunbeds.
What about vitamin D?
Despite warnings against overexposure to the sun, it remains important to get a little sun exposure as this enables our bodies to produce vitamin D.
Vitamin D is an important nutrient for the prevention of diseases such as rickets and osteomalacia. As such, sensible sun exposure is advised.
The time it takes to produce sufficient vitamin D is less than the time it takes to get sunburnt. This means we can enjoy the sun safely and maintain optimal vitamin D levels without dramatically increasing the risk of skin cancer.
Most cases of melanoma affect the skin. They usually produce changes in existing moles. A person to detect the early signs of melanoma themselves by regularly examining moles and other colored blemishes and freckles.
Any changes in the appearance of the skin should prompt further examination by a doctor. The back should also be checked regularly, especially as 1 in 3 melanomas in men occur on the back. A partner, family member, friend, or doctor can help check the back and other hard-to-see areas.
Cancer doctors are most concerned with lesions that "stand out from the crowd." The ABCDE checklist described above can help with this.
Doctors may use microscopic or photographic tools to see a lesion in more detail.
If a doctor suspects skin cancer, the patient will be referred to a cancer specialist and a biopsy will be arranged to test the lesion. A biopsy is a procedure where a sample of the lesion is taken for examination in the laboratory.