Guidelines Could Reduce Skin Cancer Over-Diagnosis
New rules separate out normal pigment cells from deadly melanomas
MONDAY, July 17, 2006 (HealthDay News) -- Not only is melanoma over-diagnosed, experts say, but there may be a more sensitive way to distinguish between this treacherous cancer and normal skin.
A team of researchers from the Mayo Clinic and the University of Pittsburgh Medical Center, publishing in the July issue of Archives of Dermatology, have characterized the differences between melanocytes (pigment-producing cells) in normal, sun-exposed skin and those in diseased tissue.
This information, they said, could be used to pinpoint actual cases of melanoma.
The study's lead researcher believes a fear of malpractice lawsuits causes many doctors to become overcautious and over-diagnose skin cancer.
"We live in a very litigious society with a lot of defensive medicine," said Dr. Ali Hendi, an assistant professor of dermatology at the Mayo Clinic in Jacksonville, Fl. "If a pathologist is looking under microscope [with these new guidelines], he is not going to feel that urge to overcall it," he reasoned.
Others are not so sure.
"It's interesting, but it's not something that will suddenly change practice," said Dr. Vijay Trisal, assistant professor of surgical oncology at City of Hope Cancer Center in Duarte, Calif.
Melanoma, which arises from melanocytes, is a particularly virulent form of cancer. It makes up 4 percent of skin cancer diagnoses and yet accounts for almost all skin cancer deaths.
According to the American Cancer Society, roughly 62,000 Americans will be diagnosed with melanoma this year, and more than 7,900 will die as a result.
Melanoma appears to be a growing problem in the United States. Diagnoses are up by a factor of 15 over the last 50 years but there has been considerable controversy over whether these diagnoses represent "true" melanoma.
The authors of this study wanted to distinguish early "real" melanoma or melanoma in situ, from normal sun-damaged skin by quantifying the characteristics of melanocytes in face and neck skin that had been subjected to chronic sun-exposure.
"Chronic sun exposure increases the number of melanocytes and there has been this gray zone where pathologists had a hard time differentiating chronically sun-exposed skin vs. very early melanoma," Hendi explained. "That's been the quandary. We decided to define what is normal."
To that end, Hendi and his colleagues looked at healthy tissue samples from 132 Caucasian patients who were undergoing Mohs surgery for non-melanoma skin cancers of the face and neck.
Mohs surgery involves removing just the diseased areas of the skin and analyzing it under a microscope so as to be able to curtail surgery as soon as the edge of the diseased tissue is reached.
The tissue samples were stained with MART-1 (melanoma antigen recognized by T cells 1 staining) immunostain, which stains only melanocytes.
"Surprisingly, when we did the study we found that a lot of the features that were previously attributed to early melanoma were actually found in normal skin," Hendi said. "That includes having several melanocytes side by side, called confluence, and having melanocytes going down the hair follicle."
"Now there is an objective measure for pathologists or Mohs surgeons," Hendi added. "We've defined what is normal."
Hendi said that he was already using these guidelines in his practice.
But, for others, the proof is not quite there.
Trisal contended, first of all, that, "I don't think we're over-diagnosing melanoma. It depends on what your benchmark is." He added that, "the main issue is whether these things that we over-diagnose behave like melanoma or like normal skin? It's not logical to be paranoid and chip off everything, everything, everything -- but missing a melanoma can be disastrous."
For more on melanoma, visit the Skin Cancer Foundation.