- Risk Factors
- Signs & Symptoms
Melanocytes are found throughout the lower part of the epidermis. They make melanin, the pigment that gives skin its natural color. When skin is exposed to the sun, melanocytes make 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. (See the PDQ summary on Intraocular (Eye) Melanoma Treatment for more information.)
There are 3 types of skin cancer:
- Basal cell skin cancer.
- Squamous cell skin cancer.
Melanoma is more aggressive than basal cell skin cancer or squamous cell skin cancer. (See 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.
Anything that increases your risk of getting a disease is called a risk factor. Having a risk factor does not mean that you will get cancer; not having risk factors doesn't mean that you will not get cancer. People who think they may be at risk should discuss this with their doctor. Risk factors for melanoma include the following:
- Unusual moles.
- Exposure to natural sunlight.
- Exposure to artificial ultraviolet light (tanning booth).
- Family or personal history of melanoma.
- Being white and older than 20 years.
- Red or blond hair.
- White or light-colored skin and freckles.
- Blue eyes.
These and other symptoms may be caused by melanoma. Other conditions may cause the same symptoms. 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).
- 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).
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).
Stages of MelanomaAfter melanoma has been diagnosed, tests are done to find out if cancer cells have spread within the skin or to other parts of the body.
The process used to find out whether cancer has spread within the skin or to other parts of the body is called staging. The information gathered from the staging process determines the stage of the disease. It is important to know the stage in order to plan treatment.
The following tests and procedures may be used in the staging process:
- Wide local excision: A surgical procedure to remove some of the normal tissue surrounding the area where melanoma was found, to check for cancer cells.
- Lymph node mapping and sentinel lymph node biopsy: Procedures in which a radioactive substance and/or blue dye is injected near the tumor. The substance or dye flows through lymph ducts to the sentinel node or nodes (the first lymph node or nodes where cancer cells are likely to have spread). The surgeon removes only the nodes with the radioactive substance or dye. A pathologist then checks the sentinel lymph nodes for cancer cells. If no cancer cells are detected, it may not be necessary to remove additional nodes.
- Chest x-ray: An x-ray of the organs and bones inside the chest. An x-ray is a type of energy beam that can go through the body and onto film, making a picture of areas inside the body.
- CT scan (CAT scan): A procedure that makes a series of detailed pictures of areas inside the body, taken from different angles. The pictures are made by a computer linked to an x-ray machine. A dye may be injected into a vein or swallowed to help the organs or tissues show up more clearly. This procedure is also called computed tomography, computerized tomography, or computerized axial tomography. For melanoma, pictures may be taken of the chest, abdomen, and pelvis.
- MRI (magnetic resonance imaging): A procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the body. This procedure is also called nuclear magnetic resonance imaging (NMRI).
- PET scan (positron emission tomography scan): A procedure to find malignant tumor cells in the body. A small amount of radioactive glucose (sugar) is injected into a vein. The PET scanner rotates around the body and makes a picture of where glucose is being used in the body. Malignant tumor cells show up brighter in the picture because they are more active and take up more glucose than normal cells do.
- Laboratory tests: Medical procedures that test samples of tissue, blood, urine, or other substances in the body. These tests help to diagnose disease, plan and check treatment, or monitor the disease over time.
The results of these tests are viewed together with the results of the tumor biopsy to determine the melanoma stage.There are three ways that cancer spreads in the body.
The three ways that cancer spreads in the body are:
- Through tissue. Cancer invades the surrounding normal tissue.
- Through the lymph system. Cancer invades the lymph system and travels through the lymph vessels to other places in the body.
- Through the blood. Cancer invades the veins and capillaries and travels through the blood to other places in the body.
When cancer cells break away from the primary (original) tumor and travel through the lymph or blood to other places in the body, another (secondary) tumor may form. This process is called metastasis. The secondary (metastatic) tumor is the same type of cancer as the primary tumor. For example, if breast cancer spreads to the bones, the cancer cells in the bones are actually breast cancer cells. The disease is metastatic breast cancer, not bone cancer.The Clark levels are used for thin tumors to describe how deep the cancer has spread into the skin:Level I
The cancer is in the epidermis only.Level II
The cancer has begun to spread into the papillary dermis (upper layer of the dermis).Level III
The cancer has spread through the papillary dermis (upper layer of the dermis) but not into the reticular dermis (lower layer of the dermis).Level IV
The cancer has spread into the reticular dermis (lower layer of the dermis).Level V
The cancer has spread into the subcutaneous layer (below the skin).The following stages are used for melanoma:Stage 0 (Melanoma in Situ)
In stage 0, abnormal melanocytes are found in the epidermis (Clark level I). These abnormal melanocytes may become cancer and spread into nearby normal tissue. Stage 0 is also called melanoma in situ.
In stage I, cancer has formed. Stage I is divided into stages IA and IB.
- Stage IA: In stage IA, the tumor is not more than 1 millimeter thick, with no ulceration. The tumor is in the epidermis and the papillary dermis (Clark level II or III).
- Stage IB: In stage IB, the tumor is either:
- not more than 1 millimeter thick and it has ulceration or it has spread through the dermis or into the subcutaneous layer (Clark level IV or V) ; or
- more than 1 but not more than 2 millimeters thick, with no ulceration.
Stage II is divided into stages IIA, IIB, and IIC.
- Stage IIA: In stage IIA, the tumor is either:
- more than 1 but not more than 2 millimeters thick, with ulceration; or
- more than 2 but not more than 4 millimeters thick, with no ulceration.
- Stage IIB: In stage IIB, the tumor is either:
- more than 2 but not more than 4 millimeters thick, with ulceration; or
- more than 4 millimeters thick, with no ulceration.
- Stage IIC: In stage IIC, the tumor is more than 4 millimeters thick, with ulceration.
In stage III, the tumor may be any thickness, with or without ulceration, and either:
- has spread into a nearby lymph vessel and may have spread into nearby lymph nodes; or
- has spread to 1 or more lymph nodes, which may be matted (not moveable).
In stage IV, the cancer has spread to other places in the body.
Recurrent melanoma is cancer that has recurred (come back) after it has been treated. The cancer may come back in the original site or in other parts of the body, such as the lungs or liver.