Science of Skin

Melanoma

Snapshot

Other common terms:  Malignant melanoma, cutaneous melanoma, skin cancer, tumour or neoplasm of the skin.

ICD-10 classification: C43

Prevalence: Common; varies geographically. 1 in 25 Australians, 1 in 5000 Americans and Europeans.

Causes/ Risk factors: Dysplastic nevi, large number of moles, individuals with family or personal history of melanoma; over the age of 50 and with certain diseases or skin type (fair complexion, sensitive or freckly skin), ultraviolet radiation. Other causes unknown.

Symptoms: Usually presents as pigmented lesion on the skin, may also appear colourless and in other areas including eyes, mouth, nose, anus and vagina.

Treatments/cures: Removal of tumour by excision or Moh’s micrographic surgery.  Chemotherapy, radiation therapy, and immunotherapy for advanced or metastasized melanoma.

Melanoma skin cancer
Melanoma skin cancer

Melanomas are malignant tumours, usually found on the skin, which can grow to invade surrounding tissue. They arise from damaged melanocytes, cells of the lower epidermis which, under physiologic conditions, produce pigment, melanin, in skin. Damage to the DNA within melanocytes leads to proliferation of the cells and unbridled growth into melanoma. Melanomas are a major cause of premature cancer death, and even though they account for only 4 percent of all dermatologic cancer, they are responsible for 80 percent of deaths from skin cancer. This is, in part, due to their ability to penetrate tissue and rapidly cause metastasis (spread). Only 14 percent of individuals diagnosed with metastatic melanoma survive beyond 5 years, therefore it is critical to diagnose melanoma in its early stages of development. Despite this, when detected early and treated appropriately there is a high survival rate for superficial spreading melanoma; 99% of patients whose melanoma is treated whilst still in situ (within the epidermis) survive beyond 10 years.

Most melanomas originate on the skin’s surface as a pigmented lesion; in this case, the disease is called cutaneous melanoma. However, they can occur all over the body, including the eye (ocular melanoma or intraocular melanoma), mouth, nose, vulva, anus, digestive tract and under finger or toe nails. They can also present both on sites that are constantly, or never, exposed to solar radiation, with the most common areas of the body being women’s legs and men’s backs.

Types of melanoma

  • Superficial spreading melanoma - appears as an irregularly pigmented spot or lesion, this is the most common type of melanoma.
  • Nodular melanomas - a fast-growing, aggressive form of tumour, these often do not follow the typical diagnosis by ABCDE. They tend to be firm and raised on a peduncle (stalk), ranging in colour from black, to red, to lacking pigment altogether. Nodular melanomas are often confused for benign growths.
  • Acral lentiginous melanoma - frequently found in dark skinned people, these melanomas often present on the soles of the feet, palms of the hand and under toe or finger nails.
  • Lentigo maligna - most commonly emerge as irregular, brown/black, facial lesions in elderly people. Lentigo maligna often remain in situ for some time before infiltrating the surrounding tissue, though when they do growth can be rapid. Without biopsy, it may be difficult for a physician to distinguish between these and benign lentigos.
  • Desmoplastic melanoma - another fast-growing, invasive tumour, these are rarely encountered.

Incidence

The incidence of melanoma varies geographically and by latitude. Australia has the highest incidence, with 1 in 25 people succumbing to the disease in their lifetime, compared to 1 in 5000 in the USA and European countries. Over ten thousand new cases of melanoma are diagnosed in Australia every year, causing approximately 1,250 deaths each year. The prevalence of malignant melanoma has doubled in the last ten years, together making up 10% of all cancers. The incidence of melanoma continues to rise in the United States, Australia, Sweden, Puerto Rico, Italy, Canada and Japan.

As with all types of skin cancer, the incidence of melanoma increases with age, though it is disproportionately high in young people, with nearly one third appearing in people under 50. In Australia melanoma is the most common type of cancer for those aged 15 to 44.  

Causes

There is much scientific evidence to indicate that exposure to UV radiation contributes to the development of malignant melanoma. Research has shown that peaks of high intensity sun exposure (e.g. sunburn in childhood) and overall lifetime exposure to ultraviolet radiation contributes substantially to melanoma risk. Individuals with pale, sun-sensitive skin who are exposed to solar UV radiation have the highest risk of melanoma. The implication of ultraviolet radiation in melanoma is very controversial and not fully understood. Some lesions, however, occur on areas of the body which rarely, or never, encounter direct sunlight. Studies continue in this area of melanoma biology as the origin of such lesions is largely a mystery. Nowadays, melanomas are seen as a group of several tumours arising on sun-exposed versus non-sun-exposed areas.

Risk factors

The following have been shown to increase the likelihood of melanoma:

  • Personal history of sun-damaged skin, melanoma or other types of skin cancer
  • Family history of melanoma
  • Dysplastic/atypical nevi - moles which are irregular or uncharacteristic in shape, colour or size
  • A large number of ordinary moles (>50)
  • Immunodeficiency (weakened immune system) resulting from medication, disease or organ transplant
  • Certain diseases, such as xeroderma pigmentosum
  • Fair complexion and sensitive skin that has a tendency to burn
  • Red or blonde hair, blue or green eyes
  • Frequency of sunburn in childhood
  • Exposure to natural UV radiation from sunlight
  • Use of artificial UV sources such as tanning beds
  • Greater than 50 years of age

Diagnosis and treatment

If a lesion is suspected to be a melanoma, usually it is removed and the mass is examined under a microscope to determine the diagnosis. Occasionally the lesion may be biopsied prior to removal if it is in a difficult or undesirable location, such as a large facial mole. The usual treatment is surgical removal by complete excision or Moh’s micrographic surgery; a detailed process which involves the removal and examination of minute skin layers for the presence of tumour cells. Depending on the stage (see Table 1.), or the distance that the melanoma has spread, removal of a large area of tissue may be required as the roots of the cancer extend down into the skin.

Table 1. Stages of melanoma (American Academy of Dermatology)

STAGE

DESCRIPTION

Stage 0; in situ

Melanoma is confined to the epidermis (top layer of skin).

Stage I-II

Melanoma is confined to the skin, but has increasing thickness and the skin may be intact or ulcerated (top layer of skin is absent).

Stage III

Melanoma has spread to a nearby lymph node and is found in increasing amounts within one or more lymph nodes.

Stage IV

Melanoma has spread to internal organs, beyond the closest lymph nodes to other lymph nodes, or areas of skin far from the original tumor.

When the cancer grows beyond the skin it is able to infiltrate surrounding tissue, lymphatic vessels and the circulatory system. From here, it can spread (metastasize) via the blood stream, which gives it access to distant organs where it can form secondary tumours (metastasis).

If melanoma has spread to a lymph node, the node(s) are usually removed to prevent its spread through the lymphatic system. The most commonly used procedure is ‘sentinel lymph node biopsy’ where the surgeon injects a dye or a radioactive chemical near the primary tumour to determine nearby lymph nodes that may contain cancerous cells. These nodes are either biopsied or entirely excised, then examined by a pathologist to establish the extent of the cancer and whether further lymph node removal is necessary.

Advanced melanomas are treated with chemotherapy, radiation therapy and immunotherapy:

Melanoma skin cancer
Melanoma skin cancer
  • Chemotherapy - the use of oral or intravenous drugs to destroy cancer cells throughout the body. Since cancer cells are constantly dividing, the anti-cancer drugs target cells undergoing replication. However, the drugs damage all cells which are replicating, which includes normal cells like those in the scalp, bones and intestines, thus chemotherapy is taxing to the patient.
  • Radiation therapy (radiotherapy or irradiation) - the use of high energy ionizing radiation (such as x-rays or gamma rays) to kill cancer cells by damaging their genetic material. Radiation can be delivered externally (via a machine), internally (an implant of radioactive material close to the tumour) or systemically (traveling right through the body). All methods aim to damage cancerous cells while limiting injury to surrounding healthy tissue.
  • Immunotherapy - typically used in conjunction with other treatments, immunotherapy involves enhancing the patients’ own immune system to attack cancerous cells. Various types of immunotherapy include the use of antibodies, cancer vaccines and immune stimulants.

Prognosis

As previously mentioned, the prognosis for melanoma patients varies depending on how far the cancer has spread. On average, 92% live for at least five year after diagnosis. The depth, or thickness, of a melanoma is the main determinant of survival rate, with 99% of people with melanoma living beyond 5 years when the tumour is detected while still restricted to the epidermis. If the spread is localised to the area of the initial tumour the five-year survival rate is 65%, this plummets to only 14% if the melanoma has metastasized extensively.

Preventative measures

Regular self-examination improves the chance of early detection and hence, more effective melanoma treatment. Those with a history of both melanoma and non-melanoma skin cancer are at greater risk of contracting new melanomas and should be particularly diligent with their skin surveillance, these individuals are often directed to undergo annual or biannual examination by a specialist. Once again, should a self-check raise any doubt, consultation with a medical expert is essential.

The first sign of melanoma is a change in the size, shape, color or feel of an existing mole. Melanoma may also appear as a new mole.

The self-examination guide can be used to detect melanomas when examining lesions on the skin looking for the following “ABCDE” features:

    A (asymmetrical): moles with an irregular shape, where one half doesn’t match the other.

    B (border): the edges are irregular, ragged or blurred.

    C (colour): the color is uneven, changing or irregular, can range between black, brown and blue.

    D (diameter): a change in size, usually an increase; growths larger than 6mm.

    E (evolving): check for any moles that appear to change shape, colour or size. 

Melanoma skin cancer
Melanoma skin cancer
Melanoma skin cancer
Melanoma skin cancer

 

Other symptoms of a changing mole to be wary of are itching, a change in texture, oozing or bleeding.

NB: If a mole or lesion is deemed suspicious it should be properly examined by a doctor or dermatologist.

Protecting skin from UV radiation is one of the most effective ways to minimize your risk of melanoma and other skin cancers. Individuals can safeguard their skin by avoiding long periods of sun exposure, especially during times of intense UV, and keeping to the shade. When time outdoors is unavoidable it is wise to cover skin with clothing, wear wide-brimmed hats, close-toed shoes and sunglasses. Liberal application of a sunscreen with a high SPF protects any areas of uncovered skin.

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