Physicians may soon have a new test to help them diagnose
melanoma with a greater degree of accuracy, researchers reported
March 9 at the annual meeting of the International Society of
Dermatopathology in San Francisco.
The test identifies chromosomal abnormalities that are common to
melanoma, the most prevalent form of skin cancer. A genetic
determination for melanoma may prove more accurate than current
methods of identifying the cancer, which involve microscopic
examination of the skin cells by a pathologist.
Like other cancers, melanoma occurs when a cell's genes become
mutated. In the case of skin cancer, this is often the result of
overexposure to the sun, though there are other contributing
factors as well.
A team of scientists led by Dr. Philip LeBoit, professor of
pathology at the University of California, San Francisco, set out
to find the genetic mutations that occur most frequently in
melanoma. They compared the genetic makeup of non-cancerous skin
cells to that of melanoma cells from 100 people.
The investigators found that on an arm of chromosome 9, 82
percent of melanoma cells are missing DNA segments. On chromosome
10, 63 percent of cells are missing other portions of DNA. Further,
on chromosome 7, about 50 percent of melanoma cells have duplicate
DNA segments.
``Now we have a common set of abnormalities for melanoma,'' said
LeBoit. ``And most tumors have two, three or four of them.''
Currently, this genetic test, called comparative genomic
hybridization, is too complex to bring to pathology labs for
regular use. However, LeBoit and his colleagues hope to simplify
the procedure to make it quicker and easier to diagnose melanoma
through use of fluorescent markers that will highlight mutated
genetic material.
``It now takes a more sophisticated molecular biology lab weeks
to months of work to get an answer for a given case,'' LeBoit said.
The fluorescent testing ``is much easier to do technically.''
About half of all melanomas develop from moles on the skin,
though they can develop on normal skin as well. The cancer starts
as a small, colored growth and can spread relatively quickly. If
untreated, the cancer can spread down through the skin, where it
can enter lymph tissue and blood vessels.
Although about 6,000 Americans each year die from melanoma, the
five-year survival rate is near 100 percent _ if the cancer is
caught early and if it hasn't spread too deep into the skin.
Therefore, it is important to have a test that can accurately
diagnose the disease quickly.
Surgery is the most common treatment for melanoma. If the
affected area is small, normally the whole area can be removed
without a biopsy. However, for larger areas in which the diagnosis
is uncertain, doctors normally take remove a small section to test
before proceeding to surgery.
A pigmented patch of skin may suspicious if it bleeds or has
become raised, grows in size or turns darker. Some melanomas
develop red, white or blue shades along with a black or brown
pigment.
