Tests for Melanoma Skin Cancer

Dermatologists often use dermoscopy, also known as dermatoscopy, epiluminescence microscopy, or surface microscopy, to get a closer look at abnormal spots on the skin. It even gives them the ability to see some structures below the surface of the skin that can’t be seen with the naked eye.

In this technique, the doctor uses a dermatoscope, which is a special magnifying lens and light source held near the skin. Sometimes a thin layer of alcohol or oil is put on the skin beforehand.

Digital images of the area can also be taken, which can be used to see if an area changes over time. In some systems, the images can be analyzed by a computer, which can help the doctor determine whether the area might be a melanoma.

RCM is another technique dermatologists can use to look closely at an abnormal area of skin. In this technique, a low-powered laser is aimed at the suspicious area. The light from the laser enters the upper layers of the skin and reflects off the structures there. A special microscope detects the light as it bounces back, which is used to create a detailed, three-dimensional image of the area. This can help the doctor determine if the area needs to be biopsied.

RCM might be especially useful for people with many unusual moles, as it can lower the number of skin biopsies these people might need. RCM might also be helpful in determining the edges of a melanoma, which could help during surgery.

Some newer handheld devices can be placed over the skin to help healthcare providers get a better idea if an abnormal area is likely to be a melanoma, without needing to remove it.

These devices might be especially helpful for primary care providers and other health professionals who don’t usually see as many skin cancers as dermatologists do.

These types of devices are placed on the skin. The tip of the device sends out beams of light or electrical signals, which bounce back off the skin cells.

The device analyzes the pattern of signals coming from the area and lets the provider know if a biopsy should be done to test for melanoma.

In this approach, a sticky patch is placed on the suspicious area. When the patch is removed it takes some of the top layers of skin with it, which can then be tested for certain gene changes that are often linked with melanoma.

If a gene change is found, a biopsy of the area can be done. If no gene changes are found, a biopsy isn’t needed, and the area can be watched instead.

For a shave biopsy, the doctor shaves off the top layers of the skin with a small surgical blade. Bleeding from the biopsy site is stopped by applying an ointment, a chemical that stops bleeding, or a small electrical current to cauterize the wound.

• A superficial shave biopsy (tangential biopsy) removes only the top layers of skin. It is useful in diagnosing many types of skin diseases and in sampling moles when the risk of melanoma is very low.
• A deep shave biopsy (saucerization) removes deeper layers of skin as well. This is the preferred type of shave biopsy if the chances of melanoma are higher.

If a shave biopsy is used for a suspected melanoma, it’s important that the biopsy blade goes deep enough to get below the suspicious area. Otherwise, if it is a melanoma, the biopsy sample might not be thick enough to measure how deeply the cancer has invaded the skin.

For a punch biopsy, the doctor uses a tool that looks like a tiny, round cookie cutter to remove a deeper sample of skin. The doctor rotates the punch biopsy tool on the skin until it cuts through all the layers of the skin. The sample is then removed, and the edges of the biopsy site are often stitched together.

To examine a tumor that might have grown into deeper layers of the skin, the doctor might use an excisional or, less often, an incisional biopsy.

• An excisional biopsy removes the entire abnormal area, along with a small margin of normal skin around it. This is usually the preferred method of biopsy for suspected melanomas.
• An incisional biopsy removes only a portion of the tumor. This might be done if the whole suspicious area can’t be removed easily.

For these types of biopsies, a surgical knife is used to make an elliptical (oval-shaped) cut through the full thickness of skin. The skin is then removed for examination, and the edges are usually stitched together.

FNA might be used to biopsy large lymph nodes near a melanoma to find out if the melanoma has spread to them.

For an FNA, the doctor uses a syringe with a thin, hollow needle to remove very small pieces of a lymph node or tumor. A local anesthetic is sometimes used to numb the area first. This test rarely causes much discomfort and does not leave a scar.

If the lymph node is just under the skin, the doctor can often feel it well enough to guide the needle into it. For a suspicious lymph node deeper in the body, an imaging test, such as ultrasound or a CT scan, is often used to help guide the needle into place.

An FNA is not as invasive as some other types of biopsies, but it might not always collect enough of a sample to tell if a suspicious area is melanoma. In these cases, a more invasive type of biopsy might be needed.

This procedure can be used to remove an enlarged lymph node through a small cut in the skin. A local anesthetic (numbing medicine) is generally used if the lymph node is just under the skin. If the lymph node is deeper in the body, you might need to be sedated or even in a deep sleep (under general anesthesia).

This type of biopsy is often done if a lymph node’s size suggests the melanoma has spread there but an FNA of the node wasn’t done or didn’t find any melanoma cells.

If melanoma has been diagnosed and has any higher-risk features, such as being at least a certain thickness, a sentinel lymph node biopsy (SLNB) is often done to see if the cancer has spread to nearby lymph nodes, which might affect treatment options.

An SLNB can be used to find the lymph nodes that are likely to be the first place the melanoma would go if it has spread. These lymph nodes are called sentinel nodes.

If a lymph node near a melanoma is larger than normal, an SLNB probably won’t be needed because it’s clear which lymph node might be affected. The enlarged node is biopsied.

Marking the sentinel lymph nodes

To find the sentinel nodes, a doctor injects a small amount of a radioactive substance into the melanoma. After giving the substance time to travel to the lymph node areas near the tumor, a special camera or a handheld detector is used to see if it collects in one or more sentinel lymph nodes.

Surgery process

Once the radioactive area has been marked, the person is taken for surgery, and usually a blue dye is injected in the same place the radioactive substance was originally injected. A small cut is then made in the marked area, and the lymph nodes are checked to find which ones became radioactive or turned blue. These sentinel nodes are removed and looked at under a microscope.

If there are no melanoma cells in the sentinel nodes, 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 nodes, the area might need to be watched closely with exams and ultrasounds or other imaging tests. If there’s a high risk that more lymph nodes in the area contain melanoma, another option might be to remove them. This is known as a completion lymph node dissection.

Ultrasound uses sound waves and their echoes to create images of the inside of your body on a computer screen. This test might be used to look at the lymph nodes near the tumor, especially if it’s not clear if they’re enlarged based on a physical exam. Ultrasound is typically fairly quick and easy to do, and it doesn’t expose you to radiation.

Ultrasound-guided needle biopsy: Ultrasound can also be used to help guide a biopsy needle into a suspicious lymph node.

A CT scan uses x-rays to make 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 show if any lymph nodes are enlarged or if organs such as the lungs or liver have suspicious spots, which might be from the spread of melanoma.

CT-guided needle biopsy: CT scans can also be used to help guide a biopsy needle into a suspicious area within the body.

This test might be done to help determine if melanoma has spread to the lungs, although a CT scan of the chest is often done instead.

MRIs use radio waves and strong magnets instead of x-rays to create detailed images of parts of your body. MRIs can be very helpful in looking at the brain and spinal cord if the doctor suspects cancer might have spread there.

A PET scan can help show whether cancer has spread to lymph nodes or other parts of the body. It is most useful in people with more advanced stages of melanoma.

For this test, you are injected with a low dose of radioactive sugar called FDG, which collects mainly in cancer cells. A special camera is then used to create a picture of areas of radioactivity in the body.

PET/CT scan: Many centers have machines that do both a PET and CT scan at the same time. This lets the doctor compare areas of higher radioactivity on the PET scan with the more detailed image from the CT scan.