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New Test Helps Unmask Melanoma

WebMD Health News

March 9, 2000 (Atlanta) -- A new test to help identify melanoma -- the deadliest and most common form of skin cancer -- will someday be available to labs across the country, according to a presentation at the annual meeting of the International Society of Dermatopathology. The test detects abnormalities that researchers at the University of California, San Francisco (UCSF), have linked with melanoma.

Melanoma is so deadly because it has the ability to spread to other parts of the body. In the U.S. in 1999, over 7,000 people died from the disease, making it the ninth most common cancer. It can be cured if it is diagnosed and treated early, before spreading.

Melanomas usually arise from moles. These moles have suddenly or gradually become larger or irregular, or have changed color or shape. Despite these changes, it is sometimes difficult for physicians to differentiate a benign, or harmless, mole from a dangerous one. This delays accurate diagnosis and treatment.

At the meeting, Philip LeBoit, MD, a professor of pathology at UCSF, presented summaries of two papers. The papers discuss a new technique that may one day help pathologists -- doctors who work in labs diagnosing diseases -- more accurately diagnose melanoma.

"This [new diagnostic technique] is how melanoma diagnosis will be made in the 21st century," LeBoit tells WebMD. Called comparative genomic hybridization (CGH), the test was developed by co-author Dan Pinkel, PhD, a professor at UCSF's Comprehensive Cancer Center. "When we began applying it, we found pretty clear-cut results," says LeBoit. "It will be especially useful in the hardest-to-diagnose cases -- those 5% of melanoma cases that even top pathologists can't distinguish from non-cancerous under the microscope."

In their study, researchers analyzed 100 samples of diagnosed melanoma cases. Using CGH, they found that all but one had detectable abnormalities. Most tumors had two, three, or four of the abnormalities, says LeBoit. CGH works by using fluorescent dyes to identify changes in cancer cell chromosomes. Chromosomes are parts of genes, the "building blocks" of the body.

In another study using CGH, researchers did not find these same abnormalities in benign moles. They conclude that pathologists can use these abnormalities as markers for melanoma.

Such cases are nerve-wracking for pathologists -- and especially for patients, says LeBoit. "They are told that the three biggest labs don't agree and all we can do is say that you may have potentially lethal disease or you might not. They have to live with this cloud over them. ... It's very difficult to plan your life with a diagnosis like that," he says.

Right now, the test is currently too sophisticated and time-consuming to be performed in labs across the country. "The problem is that right now it costs $1,000 in staff and materials and months of work to get results. Only two labs in the country can even do it," says LeBoit. Researchers are developing a simpler technique that will hopefully be available within the next two years.

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