General Information About Melanoma

Melanoma is a disease in which malignant (cancer) cells form in the skin cells called melanocytes (cells that color the skin).
Melanocytes are found throughout the lower part of the epidermis. They produce melanin, the pigment that gives skin its natural color. When skin is exposed to the sun, melanocytes produce more pigment, causing the skin to tan, or darken.

The skin is the body's largest organ. It protects against heat, sunlight, injury, and infection. The skin has 2 main layers: the epidermis (upper or outer layer) and the dermis (lower or inner layer).

When melanoma starts in the skin, the disease is called cutaneous melanoma. This PDQ summary is about cutaneous (skin) melanoma. Melanoma may also occur in the eye and is called intraocular or ocular melanoma. (Refer to the PDQ summary on Intraocular (Eye) Melanoma Treatment for more information.)

There are 3 types of skin cancer:

• Melanoma.
• Basal cell skin cancer.
• Squamous cell skin cancer.

Melanoma is more aggressive than basal cell skin cancer or squamous cell skin cancer. (Refer to the PDQ summary on Skin Cancer Treatment for more information on basal cell and squamous cell skin cancer.)

Melanoma can occur anywhere on the body.
In men, melanoma is often found on the trunk (the area from the shoulders to the hips) or the head and neck. In women, melanoma often develops on the arms and legs. Melanoma usually occurs in adults, but it is sometimes found in children and adolescents.

Unusual moles, exposure to sunlight, and health history can affect the risk of developing melanoma.
Risk factors include the following:

• Unusual moles.
• Exposure to natural sunlight, including sunburns during childhood.
• Exposure to artificial ultraviolet light (tanning booth).
• Family or personal history of melanoma.
• Red or blond hair.
• White or light-colored skin and freckles.
• Blue eyes.

Possible signs of melanoma include a change in the appearance of a mole or pigmented area.
These and other symptoms may be caused by melanoma or by other conditions. A doctor should be consulted if any of the following problems occur:

• A mole that:
  • changes in size, shape, or color.
  • has irregular edges or borders.
  • is more than 1 color.
  • is asymmetrical (if the mole is divided in half, the 2 halves are different in size or shape).
  • itches.
  • oozes, bleeds, or is ulcerated (a hole forms in the skin when the top layer of cells breaks down and the underlying tissue shows through).
• Change in pigmented (colored) skin.
• Satellite moles (new moles that grow near an existing mole).

Tests that examine the skin are used to detect (find) and diagnose melanoma.
If a mole or pigmented area of the skin changes or looks abnormal, the following tests and procedures can help detect and diagnose melanoma:

• Skin examination: A doctor or nurse examines the skin to look for moles, birthmarks, or other pigmented areas that look abnormal in color, size, shape, or texture.
• Biopsy: A local excision is done to remove as much of the suspicious mole or lesion as possible. A pathologist then looks at the tissue under a microscope to check for cancer cells. Because melanoma can be hard to diagnose, patients should consider having their biopsy sample checked by a second pathologist.

Suspicious areas should not be shaved off or cauterized (destroyed with a hot instrument, an electrical current, or a caustic substance).

Certain factors affect prognosis (chance of recovery) and treatment options.
The prognosis (chance of recovery) and treatment options depend on the following:

• The stage of melanoma (whether cancer is found in the outer layer of skin only, or has spread to the lymph nodes or to other places in the body).
• Whether there was bleeding or ulceration at the primary site.
• The location and size of the tumor.
• The patient's general health.

Although many people are successfully treated, melanoma can recur (come back)

Health Professional Version
Melanoma is a malignant tumor of melanocytes, cells that are derived from the neural crest. Although most melanomas arise in the skin, they may also arise from mucosal surfaces or at other sites to which neural crest cells migrate. Melanoma occurs predominantly in adults, and more than half of the cases arise in apparently normal areas of the skin. Early signs in a nevus that would suggest malignant change include darker or variable discoloration, itching, an increase in size, or the development of satellites. Ulceration or bleeding are later signs. Melanoma in women occurs more commonly on the extremities and in men on the trunk or head and neck, but it can arise from any site on the skin surface. A biopsy, preferably by local excision, should be performed for any suspicious lesions, and the specimens should be examined by an experienced pathologist to allow for microstaging. Suspicious lesions should never be "shaved off" or cauterized. Studies show that distinguishing between benign pigmented lesions and early melanomas can be difficult, and even experienced dermatopathologists can have differing opinions. To reduce the possibility of misdiagnosis for an individual patient, a second review by an independent qualified pathologist should be considered.[1]

Prognosis is affected by clinical and histological factors and by anatomic location of the lesion. Thickness and/or level of invasion of the melanoma, mitotic index, presence of tumor infiltrating lymphocytes, number of regional lymph nodes involved, and ulceration or bleeding at the primary site affect the prognosis.[2-5] Microscopic satellites in stage I melanoma may be a poor prognostic histologic factor, but this is controversial.[6] Patients who are younger, female, and who have melanomas on the extremities generally have a better prognosis.[2-5]

Clinical staging is based on whether the tumor has spread to regional lymph nodes or distant sites. For disease clinically confined to the primary site, the greater the thickness and depth of local invasion of the melanoma, the higher the chance of lymph node or systemic metastases and the worse the prognosis. Melanoma can spread by local extension (through lymphatics) and/or by hematogenous routes to distant sites. Any organ may be involved by metastases, but lungs and liver are common sites. The risk of relapse decreases substantially over time, although late relapses are not uncommon.[7,8]

article syndicated from NCI
The National Cancer Institute (NCI) is a component of the National Institutes of Health (NIH), one of eight agencies that compose the Public Health Service (PHS) in the Department of Health and Human Services (DHHS). The NCI, established under the National Cancer Act of 1937, is the Federal Government's principal agency for cancer research and training.