By Svetomir Markovic, M.D., Ph.D. - Mayo Clinic

DEAR MAYO CLINIC:

My uncle has been diagnosed with melanoma, but the tumor is internal with no sign of external lesions.

This is the second case I have heard of like this.

Is this getting more common? What can be done?

ANSWER:

Melanoma is getting more common overall

The type of internal melanoma you describe can develop for several reasons. But no matter what the cause, the treatment options are the same.

Melanoma is cancer of the melanin-producing cells (melanocytes) that give color to your skin. Normally, skin cells develop in a controlled and orderly way -- healthy new cells push older cells toward your skin's surface, where they die and eventually are sloughed off. But when this process goes awry, new cells may begin to grow out of control and can eventually form a mass of cancerous cells.

Internal melanoma is usually the result of melanoma that started somewhere on the skin and has spread (metastasized) to an internal organ. In many cases, the primary tumor can't be found on the skin. It may be either too small to be detected, or more commonly, it resolves on its own. The body's immune system is capable of eliminating small melanoma tumors on the skin. But all you need are several cancer cells from that tumor to invade farther into the skin and blood vessels, and melanoma can spread.

There is a subset of melanomas that originate in areas of melanin-producing cells located within the body, such as in the back of the eye, in the gall bladder and in the intestinal system. This type of melanoma is extraordinarily rare, making up less than one percent of all advanced melanomas.

We approach treatment the same way in either case. And, unfortunately, the treatment options are not very good. Over the last 40 years, researchers haven't had much success finding effective treatment options for metastatic melanoma. Melanoma accounts for only about 10 percent of all skin cancer diagnoses, but 90 percent of skin cancer deaths.

Melanoma treatment is divided into four strategies: surgery, radiation, chemotherapy and immunotherapy

Although surgery to remove the cancer cells often doesn't cure the disease, it can provide an interval of time in which we can do other things to prevent melanoma from coming back.

Radiation therapy can be helpful in some cases, but melanoma may require a higher dose of radiation than usual, and results have been mixed. Traditionally, chemotherapy alone hasn't been successful in treating metastatic melanoma.

Chemotherapy in combination with other types of therapy appears to hold more promise.

For example, a recent Mayo Clinic study showed positive results from a clinical trial of metastatic melanoma using a combination of chemotherapy and a drug that slows blood vessel growth. It turns out, melanoma tumors have a greater need for blood when they are hit with chemotherapy. By cutting off the blood supply, we can significantly increase the chemotherapy's effectiveness. We are planning to pursue these findings further with more research.

In addition, immunotherapy -- also called biological therapy -- appears to have some effect on metastatic melanoma.

Immunotherapy boosts your immune system to help your body fight the cancer. Immunotherapy treatments are made of substances produced by your body or similar substances produced in a laboratory, such as interferon and interleukin-2.

Many clinical trials are currently studying immunotherapy and melanoma.

Although we don't have reliable treatment options for metastatic melanoma at this time, there's much research in process that we hope will lead to improved treatment for this deadly disease.

Better treatment can't come soon enough, as the number of melanoma cases has been growing steadily in recent decades. Since the 1970s, it is estimated that, on average, the number of malignant melanoma cases has increased 10 percent every year worldwide.

The good news, though, is that melanoma often is highly preventable.

Using tanning beds and sun overexposure increases your risk of developing melanoma. A blistering sunburn in childhood significantly increases your subsequent melanoma risk.

Practicing sun-safe behavior does make a difference.

Also, if you have a mole that changes in appearance, see your doctor to have it checked right away.

Although melanoma that has spread is difficult to treat, if caught in its early stages, melanoma can often be surgically removed with no further treatment needed. Finally, if you have advanced melanoma, seek help from a medical center with expertise in the disease. Many have research studies offering new treatment options that may help.

-- Svetomir Markovic, M.D., Ph.D., Oncology, Mayo Clinic, Rochester, Minn.

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Rare Form of Internal Melanoma is Difficult to Treat

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