MAUI, HAWAII Good old cost-effective hematoxylin and eosin staining remains perfectly adequate for diagnosis of most melanomas in the modern molecular era, but help is on the way for the toughest cases in the form of novel tests that assess chromosome copy alterations.
These new tests include a comparative genomic hybridization, which compares the DNA in the full genome of the tumor to that of normal control DNA, and fluorescence in situ hybridization (FISH).
"These tests are just starting to become available in routine clinical practice," Dr. Maxwell A. Fung said at the annual Hawaii dermatology seminar sponsored by Skin Disease Education Foundation.
The FISH test (Abbott Laboratories), although marketed in Europe, isn't yet approved for use in the United States, but it has performed well on an investigational basis at the University of California, San Francisco, Dr. Fung said. The test probes four specific gene loci that are of particular interest because abnormalities at those sites are strongly associated with melanoma.
Three of the loci are on chromosome 6, and one is on chromosome 11. Although this combination doesn't include some of the mutations that figure prominently in melanoma, it does offer a desirable blend of technical ease along with a reported sensitivity and specificity of about 80%, said Dr. Fung of the University of California, Davis.
Distinguishing nevi from melanomas by using conventional histologic criteria is often straightforward, but there are challenges, as illustrated by a recent report by Dr. Saurabh Lodha and colleagues at Columbia University, New York.
They presented a retrospective analysis of 6 years' worth of Columbia dermatopathology consultation reports. The investigators showed that in cases in which a dermatopathologist sought consultation with a colleague regarding a tumor, there was complete agreement as to whether the lesion was a nevus or melanoma only 55% of the time (J. Cutan. Pathol. 2008;35:349-52).
"It's hard enough to decide what lesions to biopsy, but then in a small percentage of the lesions that get biopsied we just don't know what to call them," Dr. Fung said.
Dr. Fung disclosed having no relevant relationships with industry. SDEF and this news organization are owned by Elsevier.