Melanoma
What is Melanoma?
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.
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.
Types
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.
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.
Source: Skin Cancer Foundation