Melanoma Skin Cancer Overview

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Early Detection, Diagnosis, and Staging TOPICS

How is melanoma skin cancer found?

Melanoma can often be found early. There are things everyone can do to find this cancer early, when it is most likely to be cured.

Skin self-exams

It’s important to check your own skin about once a month. You should know the pattern of moles, freckles, and other marks on your skin so that you’ll notice any changes.

Self-exam is best done in front of a full-length mirror. A hand-held mirror can be used for places that are hard to see. Look at all areas, such as your palms and soles, scalp, ears, nails, and your back (in men, about 1 of every 3 melanomas is found on the back). A family member can check those hard-to-see areas like your scalp and back.

For a more on how to do a skin self-exam, see our documents Skin Cancer Prevention and Early Detection and Why You Should Know About Melanoma.

What to look for

Unusual sores, lumps, blemishes, or changes in the way an area of the skin looks or feels may be a sign of melanoma or another type of skin cancer, or a warning that it might occur.

Normal moles

A normal mole is most often an evenly colored brown, tan, or black spot on the skin. It can be either flat or raised. It can be round or oval. Moles are usually less than 1/4 inch across, or about the width of a pencil eraser. Moles can be present at birth or they can appear later.

Once a mole has developed, it will most often stay the same size, shape, and color for many years. Some moles may fade away over time.

Most people have moles, and almost all moles are harmless. But it is important to notice changes in a mole – such as its size, shape, or color – that suggest a melanoma may be starting.

Possible signs and symptoms of melanoma

The most important warning sign for melanoma is a new spot on the skin or a spot that is changing in size, shape, or color. A spot that looks different from all of the other spots on your skin can also be a warning. If you have any of these warning signs, have your skin checked by a doctor.

The ABCDE rule can help you tell a normal mole from an abnormal mole. Moles that have any of these signs should be checked by a doctor. ABCDE stands for the following:

  • A is for Asymmetry: One half of a mole or birthmark does not match the other.
  • B is for Border: The edges are irregular, ragged, notched, or blurred.
  • C is for Color: The color is not the same all over and may include shades of brown or black, or even patches of pink, red, white, or blue.
  • D is for Diameter: The spot is larger than about ¼ inch across (the size of a pencil eraser), but melanomas can be smaller than this.
  • E is for Evolving: The mole is changing in size, shape, or color.

Some melanomas don’t fit the “rules” above. It may be hard to tell if the mole is normal or not, so you should show your doctor anything that you are unsure of.

Other warning signs are:

  • A sore that does not heal
  • Spread of color from the border of a spot to the skin around it
  • Redness or a new swelling beyond the border
  • Itchiness, tenderness, or pain
  • Change in the surface of a mole – scaliness, oozing, bleeding, or a new bump or nodule

Be sure to show your doctor any areas that concern you and ask your doctor to look at areas that may be hard for you to see. Sometimes it’s hard to tell the difference between melanoma and an ordinary mole, so it’s important to show your doctor any mole that you are unsure of.

Exam by a health professional

Part of a routine cancer check-up should include a skin exam by a doctor or trained health professional. Regular skin exams are especially important for people who are at higher risk of melanoma, such as people with a strong family history or who have had melanoma before.

If there is any reason to suspect that you have a melanoma, your doctor will do more exams and tests to find out if it is melanoma or something else. You might also be referred to a doctor who is an expert in skin diseases (called a dermatologist) for some of these tests.

Medical history and physical exam

The doctor will likely ask about your symptoms and risk factors. This will include when you first saw the mark on your skin, if it has changed in size or the way it looks, and if it is causing any symptoms (pain, itching, bleeding, etc.). You may also be asked about whether anyone in your family has had skin cancer and about past UV light exposure.

During the exam, the doctor will note the size, shape, color, and texture of the area of concern, and whether there is bleeding or scaling. The rest of your body may be checked for other spots and moles. The doctor may also feel nearby lymph nodes under the skin, like those in the groin, underarm, or neck. Enlarged lymph nodes might suggest the spread of a melanoma.

The doctor might use a special magnifying lens and light source held near the skin. Sometimes a thin layer of oil is put on the skin. A picture of the spot may be taken. These tests, when used by a doctor who has experience with them, can improve the chances in finding melanomas early. They also often show that a spot on the skin is not cancer, so no more testing is needed.

Skin biopsy

If the doctor thinks a spot might be a melanoma, he or she will take a sample of the skin to look at under a microscope. This is called a biopsy. There are different ways to do a skin biopsy. The choice depends on the size of the area of concern and where it is on the body. All methods are likely to leave at least a small scar. Since different methods leave different types of scars, you should ask the doctor about this before the biopsy is done. No matter which type of biopsy is done, as much of the area in question should be removed as possible so that an exact diagnosis can be made.

The skin around the area of the biopsy will be numbed before the biopsy. You will feel a little stinging as the medicine goes in, but you should not feel any pain during the biopsy.

Shave biopsy: After numbing the area, the doctor shaves off the top layers of the skin. Bleeding from the biopsy site is then stopped by applying an ointment or a small electric current to cauterize the wound.

A shave biopsy is useful for many types of skin diseases and in sampling moles when the risk of melanoma is very low. A shave biopsy is not usually done if the doctor strongly suspects melanoma unless the biopsy blade goes deep enough to get below the area in question. If it doesn’t, it may not be thick enough to measure how deeply a melanoma has invaded the skin.

Punch biopsy: In a punch biopsy a deeper sample of skin is removed. The doctor uses a tool that looks like a tiny round cookie cutter. Once the skin is numbed, the doctor turns the tool on the surface of the skin until it cuts through all the layers of the skin and takes out a sample of tissue. The edges of the skin are often stitched together.

Incisional and excisional biopsies: If the doctor has to look at a tumor in the deeper layers of the skin, an incisional or excisional biopsy will be done. The skin will be numbed before the biopsy. A surgical knife is used to cut through the full thickness of skin. A wedge of skin is removed, and the edges of the cut are sewn together.

An incisional biopsy removes only part of the tumor. If the whole tumor is removed, it is called an excisional biopsy. Excisional biopsy is most often used when it can be done.

Biopsies of melanoma that may have spread

If melanoma has already been found on the skin, nearby lymph nodes or other areas may be biopsied to see if the cancer has spread.

Rarely, some melanomas spread so fast that a person could have cancer in the lymph nodes, lungs, brain, or other places while the first skin melanoma is still small. Sometimes these tumors are found before a spot on the skin is found. In other cases they may be found long after a skin melanoma has been removed, so it’s not clear whether it is the same cancer. In still other cases, metastatic melanoma may be found without ever finding a melanoma on the skin. This may be because some skin lesions go away on their own (without any treatment) after some of their cells have spread to other parts of the body. Melanoma can also start in internal organs, but this is very rare.

If melanoma has spread widely throughout the body, it may not be possible to tell which tumor was the first one. When this happens, melanoma in those organs might be confused with a cancer starting in that organ. For example, melanoma that has spread to the lung might be confused with a cancer that starts in the lung. Special lab tests can be done on biopsy samples to tell whether it is a melanoma or some other kind of cancer. This is important because different treatments are used for different cancers.

Fine needle aspiration biopsy (FNA): This kind of biopsy is not used to diagnose a suspicious mole, but it can sometimes be used if the doctor thinks the melanoma has spread to nearby lymph nodes or to organs like the lung or liver. A thin, hollow needle is used to remove very small tissue samples from the tumor. The test rarely causes much discomfort and does not leave a scar. But it may not always collect enough of a sample to tell if melanoma is present.

Surgical (excisional) lymph node biopsy: For this type of biopsy a swollen lymph node is removed through a small cut (incision). Numbing medicine is often put on the skin if the lymph node is near the surface of the body. But if the lymph node is deeper in the body, you may need to be made drowsy or even put into a deep sleep (using general anesthesia). It is often done if a lymph node’s size suggests the melanoma has spread there but either an FNA was not done or it did not show any cancer cells.

Sentinel lymph node biopsy: If melanoma has been diagnosed and has any concerning features (such as being at least a certain thickness), a sentinel lymph node biopsy is often done to find out if the cancer has spread to nearby lymph nodes. If so, it could affect treatment options. This test can find the lymph nodes that drain lymph fluid from the area of the skin where the melanoma started. These sentinel lymph nodes are likely to be the first place the melanoma would go if it has spread.

To find the sentinel lymph nodes, the surgeon injects a radioactive liquid (and sometimes a blue dye) into the area of the melanoma. The lymph nodes are then checked for radioactivity to find which ones are the first to drain fluid from the skin near the melanoma. A small cut is made in the identified lymph node area. The lymph nodes are then checked to find which one(s) absorbed radiation and turned blue. When these lymph nodes have been found, they are taken out and sent to a lab to be looked at under a microscope. If cancer cells are found, the rest of the lymph nodes in this area are removed, too. If the sentinel nodes do not contain cancer cells, further lymph node surgery is not needed.

If a lymph node near a melanoma is very large, this test may not be needed. The enlarged node is simply biopsied.

Lab tests of biopsy samples

After a biopsy, the samples are sent to a lab to be looked at under a microscope. If the doctor can’t tell for sure if the sample contains melanoma cells just by looking at it, special tests may be done on the cells to try to confirm the diagnosis.

If the samples do contain melanoma, the doctor will look at certain features such as the tumor thickness the portion of cells that are actively dividing. These features help define the stage of the melanoma (see the section “How is melanoma of the skin staged?”), which in turn affects treatment options and the outlooks (prognosis) for the patient.

For advanced melanomas, tests may be done to see if the cancer cells have changes in genes such as the BRAF gene. This could help define which treatments might work. (See the section “Targeted therapy for melanoma skin cancer.”)

Imaging tests

Imaging tests are done to create pictures of the inside of the body. They are used to look for the spread of melanoma. They are not needed for people with very early melanoma, which is not likely to have spread. These tests may also be done to help find out how well treatment is working or to look for signs that the cancer has come back after treatment.

Chest x-ray: This test may be done to see if the cancer has spread to the lungs.

CT (computed tomography) scan: This test can help show if any lymph nodes are enlarged or if organs such as the lungs or liver have spots that might be from the spread of melanoma.

CT scans use many x-ray images that are combined by a computer to give a detailed, cross-sectional view of the body. You may be asked to drink a special liquid or get a kind of dye put into your vein, which can help better outline structures in your body.

A CT scanner has been described as a large donut, with a narrow table that slides in and out of the middle opening. You need to lie still on the table while the scan is being done. CT scans take longer than regular x-rays, and you might feel a bit confined by the ring while the pictures are being taken.

CT scans can also be used to guide a needle during a biopsy. For this, you stay on the CT scanning table while a biopsy needle is moved through the skin and toward the mass.

MRI (magnetic resonance imaging): This is like a CT scan except that it uses radio waves and strong magnets to make a picture of your insides. MRI scans are very helpful in looking at the brain and spinal cord.

They take longer than CT scans – often up to an hour. You may have to lie inside a narrow tube, which is confining and can upset some people. Newer, open MRI machines can sometimes be used instead. The MRI machine also makes loud buzzing and thumping noises, so some places provide headphones to block this out.

PET (positron emission tomography) scan: In this test, a special kind of radioactive sugar is put into a vein. The sugar collects in areas that have cancer, and a scanner can spot these areas. This test can be useful to see if the cancer has spread to lymph nodes or other parts of the body. It can also help when the doctor thinks the cancer has spread but doesn’t know where. Doctors find it most useful in people with advanced stages of melanoma. It is not very helpful in people with early stage melanoma. Some newer machines do PET scans and CT scans at the same time.

To learn more about these imaging tests, see our document Imaging (Radiology) Tests.

Blood tests

Blood tests aren’t used to find melanoma, but some tests may be done before or during treatment, especially for more advanced melanomas.

Doctors often test for blood levels of a substance called lactate dehydrogenase (LDH) before treatment. If the melanoma has spread to distant parts of the body, a higher than normal level of LDH is a sign that the cancer may be harder to treat. This affects the stage of the cancer.

Some other tests of blood cell counts and blood chemistry levels may be done in a person who has advanced melanoma to see how well the bone marrow (where new blood cells are made), liver, and kidneys are working during treatment.


Last Medical Review: 02/19/2014
Last Revised: 09/16/2014