Diagnosing Metastatic Melanoma: What Doctors Look For

Here’s how doctors know if this dangerous type of skin cancer has spread.

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Melanoma is the most dangerous form of skin cancer, but catching it early can significantly improve treatment outcomes, survival rate, and risk of recurrence. In fact, if the melanoma has not spread beyond the skin, “up to 50 percent of the patients can be cured, especially if it's captured early,” says Kaveh Alizadeh, MD, a plastic and reconstructive surgeon in New York.

Metastatic melanoma means the cancer has spread beyond the skin and is affecting distant lymph nodes and organs. “Melanoma unfortunately can spread to many, many locations. It can go to the lungs, it can go to the brain—up to a third of the patients can have metastases of melanoma to the brain,” says Dr. Alizadeh.

That’s why getting your skin checked and getting a proper—and prompt—melanoma diagnosis is critical. Waiting and avoiding diagnosis or treatment may allow the cancer cells to spread and become more advanced.

How Doctors Prevent Melanoma From Spreading

The first line of treatment for melanoma is surgical excision, meaning the visible cancer on the skin is removed surgically. However, for some patients, this does not mean they’re cancer-free.

“If you look in the blood of patients with stage three melanoma—surgically free of disease, there’s no visible tumor—in half of them at least, or more, you would detect circulating tumor cells,” says Jeffrey Weber, MD, PhD, medical oncologist and melanoma researcher at Perlmutter Cancer Center at NYU Langone Health.

For these patients, the likelihood of the cancer returning is high. Because of this, doctors often recommend adjuvant therapy to treat melanoma, which are treatments that help prevent the cancer from spreading.

How Metastatic Melanoma Is Diagnosed

Whether a patient is undergoing adjuvant therapy to treat melanoma—which requires regular follow-up appointments—or is being diagnosed for the first time, a doctor may perform these tests to see if the melanoma has spread:

First, your doctor may examine your medical history, ask about your symptoms, or check on the surgery site for bleeding or changes. They may also perform a physical exam, where they’ll feel the lymph nodes under the skin of the neck, underarm, or groin. If lymph nodes are enlarged and swollen, it may indicate that the cancer has spread.

Then, your doctor may suggest a sentinel lymph node biopsy.

Sentinel lymph node biopsy is a way to check for lymph node involvement. “Sentinel nodes” is a term for the lymph nodes that are most likely to be affected by melanoma if it were to spread. It uses a blue dye injected into the melanoma area to see which lymph nodes the dye travels to. Those nodes are then removed and examined under a microscope.

“If that node is positive, that tells you that the potential for a spread is high, which is why it's called sentinel node. It's sort of … the first signal that this may have spread,” says Dr. Alizadeh. If no cancer is found, lymph node status is considered negative.

If sentinel lymph node biopsy was positive, your doctor may recommend a complete lymph node dissection.

Complete lymph node dissection, or lymphadenectomy, is a surgical procedure in which the lymph nodes are removed and a sample of tissue is checked under a microscope for signs of cancer. “That [complete] lymph node dissection allows you to examine all the nodes that could potentially have been a cause of metastasis,” says Dr. Alizadeh.

If the melanoma has spread, then doctors will discuss your treatment options for metastatic melanoma. “This is an exciting time to be able to not only have a conversation with patients that are in the early stage of melanoma, where we can get them a cure, but even late-stage or advanced-stage patients, because we can offer them a number of different treatments,” says Dr. Alizadeh.