Melanoma: Stages, types, causes, and pictures

Melanoma is not the most common type of skin cancer, but it is the most serious because it often spreads. Risk factors for melanoma include overexposure to the sun.

This article explains the symptoms of melanoma, how it is diagnosed, and how it is treated. We also explain how best to prevent melanoma.

Fast facts on melanoma

The incidence of melanoma appears to be increasing for people under the age of 40 years, especially women.

Avoiding sunburn is an effective way to reduce the risk of skin cancer.

Self-monitoring of moles and other markings on the skin can help with early detection.

What is melanoma?

Melanoma skin cancer image
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.

Stages

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.

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Causes

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.

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