Melanoma is a disease in which malignant (cancer) cells form in melanocytes (cells that color the skin).

The skin is the body’s largest organ. It protects against heat, sunlight, injury, and infection. Skin also helps control body temperature and stores water, fat, and vitamin D. The skin has several layers, but the two main layers are the epidermis (upper or outer layer) and the dermis (lower or inner layer). Skin cancer begins in the epidermis, which is made up of three kinds of cells:

• Squamous cells: Thin, flat cells that form the top layer of the epidermis.
• Basal cells: Round cells under the squamous cells.
• Melanocytes: Cells that make melanin and are found in the lower part of the epidermis. Melanin is the pigment that gives skin its natural color. When skin is exposed to the sun or artificial light, melanocytes make more pigment and cause the skin to darken.

There are different types of cancer that start in the skin.

There are two main forms of skin cancer: melanoma and nonmelanoma.

Melanoma is a rare form of skin cancer. It is more likely to invade nearby tissues and spread to other parts of the body than other types of skin cancer. When melanoma starts in the skin, it is called cutaneous melanoma. Melanoma may also occur in mucous membranes (thin, moist layers of tissue that cover surfaces such as the lips). This summary is about cutaneous (skin) melanoma and melanoma that affects the mucous membranes.

Before age 50, rates of melanoma are higher in women than in men. After age 50, rates of melanoma are much higher in men. Melanoma is most common in adults, but it is sometimes found in children and adolescents. Learn more about Childhood Melanoma Treatment.

The most common types of skin cancer are basal cell carcinoma and squamous cell carcinoma. They are nonmelanoma skin cancers. Nonmelanoma skin cancers rarely spread to other parts of the body. Learn more about Skin Cancer Treatment.

Melanoma can occur anywhere on the skin.

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 forms most often on the arms and legs.

When melanoma occurs in the eye, it is called intraocular or ocular melanoma. Learn more about Intraocular (Uveal) Melanoma Treatment.

Unusual moles, exposure to sunlight, and health history can affect the risk of melanoma.

A risk factor is anything that increases the chance of getting a disease. Some risk factors for melanoma, such as tanning bed use, can be changed. However, risk factors also include things people cannot change, like their genetics and their family history. Learning about risk factors for melanoma can help you make changes that might lower your risk of getting it.

Risk factors for melanoma include:

• having a fair complexion, which includes:
  • fair skin that freckles and burns easily, does not tan, or tans poorly
  • blue or green or other light-colored eyes
  • red or blond hair
• being exposed to natural sunlight or artificial sunlight (such as from tanning beds)
• being exposed to certain factors, such as radiation, solvents, vinyl chloride, and PCBs, in the environment (the air, your home or workplace, and your food and water)
• having a history of many blistering sunburns, especially as a child or teenager
• having several large or many small moles
• having a family history of unusual moles (atypical nevus syndrome)
• having a family or personal history of melanoma
• being White
• having a weakened immune system
• having certain changes in the genes that are linked to melanoma

Being White or having a fair complexion increases the risk of melanoma, but anyone can have melanoma, including people with dark skin.

Learn more about risk factors for melanoma at Genetics of Skin Cancer and Skin Cancer Prevention.

Signs of melanoma include a change in the way a mole or pigmented area looks.

These and other signs and symptoms may be caused by melanoma or by other conditions. Check with your doctor if you have:

• a mole that:
  • changes in size, shape, or color
  • has irregular edges or borders
  • is more than one 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 tissue below shows through)
• a change in pigmented (colored) skin
• satellite moles (new moles that grow near an existing mole)

The acronym ABCDE can help you remember the signs of melanoma:

• Asymmetrical
• Border
• Color
• Diameter (melanoma is usually larger than 6 millimeters)
• Evolving (the mole changes in size, shape, or color over time

Find pictures and descriptions of common moles and melanoma at Common Moles, Dysplastic Nevi, and Risk of Melanoma.

Tests that examine the skin are used to diagnose melanoma.

Melanoma is usually diagnosed with tests that examine the skin. The process used to find out if cancer cells have spread beyond the skin is called staging. To plan treatment, it is important to know the stage of the disease.

In addition to asking about your personal and family health history and doing a physical exam, your doctor may perform the following tests and procedures to find and diagnose melanoma:

• Skin exam is an exam where a doctor or nurse checks the skin for moles, birthmarks, or other pigmented areas that look abnormal in color, size, shape, or texture.
• Biopsy is the removal of cells or tissues so they can be viewed under a microscope to check for signs of cancer. It can be hard to tell the difference between a colored mole and an early melanoma lesion. Patients may want to have the sample of tissue checked by a second pathologist. If the abnormal mole or lesion is cancer, the sample of tissue may also be tested for certain gene changes. This may help to plan treatment. Learn about the type of information that can be found in a pathologist's report about the cells or tissue removed during a biopsy at Pathology Reports

  There are four main types of skin biopsies. The type of biopsy done depends on where the abnormal area formed and the size of the area.

  • Shave biopsy uses a sterile razor blade to "shave off" the growth.
  • Punch biopsy uses a special instrument called a punch or a trephine to remove a circle of tissue from the growth.
  • Incisional biopsy uses a scalpel to remove part of a growth.
  • Excisional biopsy uses a scalpel to remove the entire growth.

After melanoma has been diagnosed, tests may be 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.

For melanoma that is not likely to spread to other parts of the body or recur, more tests may not be needed. For melanoma that is likely to spread to other parts of the body or recur, the following tests and procedures may be done after surgery to remove the melanoma:

• Lymph node mapping and sentinel lymph node biopsy includes the removal of the sentinel lymph node during surgery. The sentinel lymph node is the first lymph node in a group of lymph nodes to receive lymphatic drainage from the primary tumor. It is the first lymph node the cancer is likely to spread to from the primary tumor. A radioactive substance or blue dye is injected near the tumor. The substance or dye flows through the lymph ducts to the lymph nodes. The first lymph node to receive the substance or dye is removed. A pathologist views the tissue under a microscope to look for cancer cells. If cancer cells are not found, it may not be necessary to remove more lymph nodes. Sometimes, a sentinel lymph node is found in more than one group of nodes.
• CT scan (CAT scan) is 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 neck, chest, abdomen, and pelvis.
• PET scan (positron emission tomography scan) is 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.
• MRI (magnetic resonance imaging) with gadolinium is a procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the body, such as the brain. A substance called gadolinium is injected into a vein. The gadolinium collects around the cancer cells so they show up brighter in the picture. This procedure is also called nuclear magnetic resonance imaging (NMRI).
• Ultrasound exam is a procedure in which high-energy sound waves (ultrasound) are bounced off internal tissues, such as lymph nodes, or organs and make echoes. The echoes form a picture of body tissues called a sonogram. The picture can be printed to be looked at later.
• Blood chemistry studies is a procedure in which a blood sample is checked to measure the amounts of certain substances released into the blood by organs and tissues in the body. For melanoma, the blood is checked for an enzyme called lactate dehydrogenase (LDH). High LDH levels may predict a poor response to treatment in people with metastatic disease.

The results of these tests are viewed together with the results of the tumor biopsy to find out the stage of the melanoma.

Some people decide to get a second opinion.

You may want to get a second opinion to confirm your melanoma diagnosis and treatment plan. If you seek a second opinion, you will need to get medical test results and reports from the first doctor to share with the second doctor. The second doctor will review the pathology report, slides, and scans. They may agree with the first doctor, suggest changes or another treatment approach, or provide more information about your cancer.

To learn more about choosing a doctor and getting a second opinion, see Finding Cancer Care. You can contact NCI's Cancer Information Service via chat, email, or phone (both in English and Spanish) for help finding a doctor, hospital, or getting a second opinion. For questions you might want to ask at your appointments, see Questions to Ask Your Doctor about Cancer.

Certain factors affect prognosis (chance of recovery) and treatment options.

The prognosis and treatment options depend on:

• the thickness of the tumor and where it is in the body
• whether there was bleeding or ulceration of the tumor
• how much cancer is in the lymph nodes
• the number of places and where cancer has spread to in the body
• the level of lactate dehydrogenase (LDH) in the blood
• whether the cancer has certain mutations (changes) in a gene called BRAF
• your age and general health