If an abnormal area of skin raises the possibility of skin cancer, certain medical exams and tests may be used to find out if it is melanoma, non-melanoma skin cancer, or some other skin condition. If melanoma is found, other tests may be done to determine if it has spread to other areas of the body.

Medical history and physical exam

Usually the first step is for your doctor to take your medical history. The doctor probably will ask your age, when the mark on the skin first appeared, and whether it has changed in size or appearance. You may also be asked about past exposures to known causes of skin cancer and whether anyone in your family has had skin cancer.

During the physical exam, your doctor will note the size, shape, color, and texture of the area(s) in question, and whether there is bleeding or scaling. The rest of your body will be checked for spots and moles that may be related to skin cancer.

The doctor may also feel the lymph nodes (small, bean shaped collections of immune cells) under the skin in the groin, underarm, or neck near the abnormal area. Enlarged lymph nodes might suggest that any melanoma present may have spread.

If you are being seen by your primary doctor and melanoma is suspected, you may be referred to a dermatologist, who will look at the area more closely.

Along with a standard physical exam, many dermatologists use a technique called dermatoscopy (also called epiluminescence microscopy [ELM] or surface microscopy) to see spots on the skin more clearly. This involves the use of a dermatoscope, which is a special magnifying lens and light source held near the skin. Sometimes a thin layer of oil is used with this instrument. A digital or photographic image of the spot may be taken. The use of these tests by experienced dermatologists can improve accuracy in finding melanomas early. It can also often reassure you that a lesion is benign (non-cancerous) without the need for a biopsy.

Skin biopsy

If the doctor thinks a melanoma might be present, he or she will take a sample of skin from the suspicious area for exam under a microscope. This is called a skin biopsy. Different methods can be used for a skin biopsy. The choice depends on the size of the affected area and its location on your body.

Skin biopsies are done using a local anesthetic (numbing medicine), which is injected into the area with a very small needle. You will likely feel a small prick and a little stinging as the medicine is injected, but should not feel any pain during it or during the biopsy.

Any biopsy is likely to leave a scar. Since different methods produce different types of scars, you should ask the doctor about biopsies and scarring before the procedure is done.

Incisional and excisional biopsies

If the doctor has to examine a tumor that may have grown into the deeper layers of the skin, he or she will perform an incisional or excisional biopsy. An incisional biopsy removes only a portion of the tumor. An excisional biopsy removes the entire tumor, and is usually the preferred method of biopsy for suspected melanomas. After numbing the area with a local anesthetic, a surgical knife is used to cut through the full thickness of skin. A wedge or sliver of skin is removed for further examination, and the edges of the wound are sewn together.

Shave biopsy

For this type of biopsy, the doctor first numbs the area with a local anesthetic. The doctor then "shaves" off the top layers of the skin (the epidermis and the outer part of the dermis) with a surgical blade. A shave biopsy is useful in diagnosing many types of skin diseases and in sampling moles when the risk of melanoma is very low. But it is not generally recommended if a melanoma is suspected because a shave biopsy sample may not be thick enough to measure how deeply the melanoma has invaded the skin.

Punch biopsy

A punch biopsy removes a deeper sample of skin but is more limited in the diameter of the sample that can be taken. The doctor uses a tool that looks like a tiny round cookie cutter. Once the skin is numbed with a local anesthetic (numbing medicine), the doctor rotates the punch biopsy tool on the surface of the skin until it cuts through all the layers of the skin, including the dermis, epidermis, and the upper parts of the subcutis.

Examining the biopsy samples

All skin biopsy samples are looked at under a microscope. The skin sample is sent to a pathologist, a doctor who has been specially trained in the microscopic examination and diagnosis of tissue samples. Often, the sample is sent to a dermatopathologist, a doctor who has special training in making diagnoses from skin samples.

Biopsies of melanoma that has spread

Biopsies of areas other than the skin may be needed in some cases. For example, if melanoma has already been diagnosed in a skin lesion, biopsies of nearby lymph nodes may be done to see if the cancer has spread that far (or potentially farther).

In rare cases, biopsies may be needed to figure out what type of cancer someone has. Some melanomas may spread so quickly that they reach the lymph nodes, lungs, brain, or other areas while the original skin melanoma is still small. Sometimes these tumors are found before the skin lesion is discovered. In other cases they may be found long after a skin melanoma has been removed, so it's not clear that it might be the same cancer. In still other cases, metastatic melanoma may be found without ever finding a skin lesion. 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, although this is quite rare, and if melanoma has spread extensively throughout the body, it may not be possible to tell which tumor was the first one.

When such spread has occurred, the metastatic melanoma in certain 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 primary lung cancer (cancer that starts in the lung).

Special tests can be done on the biopsy samples that can tell whether it is a melanoma or some other kind of cancer. This is important because different cancers are often given different treatments.

These types of biopsies may be more involved than those used to sample the skin.

Fine needle aspiration biopsy

A fine needle aspiration (FNA) biopsy is not used for diagnosis of a suspicious mole, but it may be used to biopsy large lymph nodes near a melanoma to find out if the melanoma has spread to them. This type of biopsy uses a syringe with a thin needle to remove very small tissue fragments from a tumor. The needle is smaller than the needle used for a blood test. A local anesthetic is sometimes used to numb the area first. This test rarely causes much discomfort and does not leave a scar.

Sometimes a computed tomography (CT) scan (a special type of x-ray; see below) is used to guide a needle into a suspicious lymph node deeper in the body or a tumor in an internal organ, such as the lung or liver. This test, called a CT-guided needle biopsy, can be used if the doctor suspects the melanoma has spread to these areas.

Surgical (excisional) lymph node biopsy

This procedure can be used to remove an enlarged lymph node through a small skin incision. Local anesthetic is generally used. This is often done if a lymph node's size suggests spread of melanoma but an FNA biopsy of the node did not find any melanoma cells.

Sentinel lymph node mapping and biopsy

This has become a common procedure to determine if melanoma has spread to the lymph nodes. This procedure can find the lymph nodes that drain lymph fluid from the area of the skin where the melanoma started. If the melanoma has spread, these lymph nodes are usually the first place it will go. That is why these lymph nodes are called sentinel nodes (they stand sentinel, or watch, over the tumor, so to speak).

To map the sentinel lymph node (or nodes), some time before surgery the doctor injects a small amount of radioactive material and usually a blue dye into the area of the melanoma. By checking various lymph node areas with a radioactivity detector (which works like a Geiger counter), the doctor can see what group of lymph nodes the melanoma is most likely to travel to. The surgeon makes a small incision in the identified lymph node area. The lymph nodes are then checked to find which one(s) turned blue or became radioactive. When the sentinel node has been found, it is removed and looked at under a microscope. If the sentinel node does not contain melanoma cells, no more lymph node surgery is needed because it is very unlikely the melanoma would have spread beyond this point. If melanoma cells are found in the sentinel node, the remaining lymph nodes in this area are removed and looked at as well. This is known as a lymph node dissection.

If a lymph node near a melanoma is abnormally large, the sentinel node procedure may not be needed. The enlarged node is simply biopsied.

Imaging tests

Imaging tests use x-rays, magnetic fields, or radioactive substances to create pictures of the inside of the body. They are used mainly to look for the possible spread of melanoma to lymph nodes or other organs in the body. They are not needed in people with very early-stage melanoma, which is very unlikely to have spread.

Chest x-ray

This test may be done to help determine whether melanoma has spread to the lungs.

Computed tomography (CT)

The CT scan is a type of x-ray test that produces detailed, cross-sectional images of your body. Unlike a regular x-ray, CT scans can show the detail in soft tissues (such as internal organs). This test can help tell if any lymph nodes or organs such as the liver are enlarged, which might be due to the spread of melanoma. It can also better identify spread to the lung than the standard chest x-ray.

Instead of taking one picture, as does a regular x-ray, a CT scanner takes many pictures as it rotates around you. A computer then combines these pictures into detailed images of the part of your body that is being studied.

You may receive an intravenous (IV) injection of a dye, or radiocontrast agent, which helps better outline structures in your body. You may also be asked to drink 1 to 2 pints of a solution of contrast material. This helps outline the intestine so that it is not mistaken for tumors if your doctor is looking for abnormal areas in your abdomen.

The IV injection of contrast dye can cause some flushing (a feeling of warmth, especially in the face). Some people are allergic and get hives or, rarely, more serious reactions like trouble breathing and low blood pressure. Be sure to tell the doctor if you have ever had a reaction to any contrast material used for x-rays.

CT scans take longer than regular x-rays. You need to lie still on a table while they are being done. During the test, the table moves in and out of the scanner, a ring-shaped machine that completely surrounds the table. You might feel a bit confined by the ring you have to lie in when the pictures are being taken.

In recent years, spiral CT (also known as helical CT) has become available in many medical centers. This type of CT scan uses a faster machine. The scanner part of the machine rotates around the body continuously, allowing doctors to collect the images much more quickly than with standard CT. This lowers the chance of "blurred" images occurring as a result of breathing motion. It also lowers the dose of radiation received during the test. The biggest advantage may be that the "slices" it images are thinner, which yields more detailed pictures and allows doctors to look at suspicious areas from different angles.

CT-guided needle biopsy: CT scans can also be used to guide a biopsy needle precisely into a suspected metastasis. For this procedure, the patient remains on the CT scanning table while a radiologist moves a biopsy needle through the skin and toward the location of the mass. CT scans are repeated until the needle is within the mass. A fine needle biopsy sample (tiny fragment of tissue) or a core needle biopsy sample (a thin cylinder of tissue about ½-inch long and less than 1/8-inch in diameter) is then removed to be looked at under a microscope.

Magnetic resonance imaging (MRI)

MRI scans use radio waves and strong magnets instead of x-rays. The energy from the radio waves is absorbed by the body and then released in a pattern formed by the type of body tissue and by certain diseases. A computer translates the pattern into a very detailed image of parts of the body. A contrast material might be injected, just as with CT scans, but is used less often.

MRI scans are very helpful in looking at the brain and spinal cord.

MRI scans 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 people with a fear of enclosed spaces. Newer, "open" MRI machines can help with this if needed. The MRI machine makes loud buzzing noises that you may find disturbing. Some places provide headphones to block this out.

Positron emission tomography (PET)

PET scans involve injecting glucose (a form of sugar) that contains a radioactive atom into the blood. Because cancer cells in the body are growing rapidly, they absorb large amounts of the radioactive sugar. A special camera can then create a picture of areas of radioactivity in the body.

The picture is not finely detailed like a CT or MRI scan, but it provides helpful information. This test can be useful to see if the cancer has spread to lymph nodes. PET scans are also useful when your doctor thinks the cancer has spread but doesn't know to 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 are able to perform both a PET and CT scan at the same time (PET/CT scan). This allows the radiologist to compare areas of higher radioactivity on the PET with the appearance of that area on the CT.

Bone scan

A bone scan is used to look for spread of cancer to the bones, but it is rarely used in melanoma. It is only done when other test results or symptoms suggest that the cancer may have spread to the bones.

For this test, the radiologist injects a slightly radioactive chemical into the bloodstream, which collects in the bones at sites of cancer or other areas where there is metabolic activity. You then lie on a table for about 30 minutes while a special camera detects the radioactivity and creates a picture of your skeleton. The images from these scans are seen as "hot spots" in the body, but they don't provide much detail. If an area lights up on the scan, x-rays of the affected area can be done to get a more detailed look. If melanoma is a possibility, a biopsy of the area may be needed to confirm this.

Last Medical Review: 06/05/2008
Last Revised: 05/14/2009