Monday, July 9, 2007
Melanoma or a Benign Mole?
The biggest malpractice risk for physicians is "failure to diagnose". If a patient shows up with a skin growth, most physicians will reach for the scalpel and remove it or biopsy it rather than take the risk of missing a cancer. But only 3-10% of suspicious moles are melanomas so that means a lot of unnecessary surgeries and costs are incurred.
A pilot study has shown that applying a simple tape to suspicious pigmented lesions and pulling off RNA for genetic analysis can differentiate melanoma from benign moles. The non-invasive test also seems to differentiate high-risk from low-risk dysplastic nevi. These dysplastic nevi are not cancer, but they require extensive follow-up and biopsies to make sure they don't change into a malignancy. The cost and inconvenience are enormous.
The tape stripping method is called Epidermal Genetic Information Retrieval. In this study they tape stripped each lesion up to four times and also tape-stripped uninvolved skin on each patient to serve as control specimens. All the lesions were then biopsied and sent for pathology examination. They found the harvested RNA is stable at room temperatures for 72 hours, meaning it can be harvested, stored and shipped for analysis without degrading.
The researchers were able to use genetic isolation to differentiate melanomas, high-risk and low-risk dysplastic nevi from normal skin.
This technique is not ready for prime time, but it gives us a glimpse into the future when we will be harvesting RNA and DNA and making diagnosis and treatment decisions, without ever invading the skin. The way we practice medicine now will look very primitive in the not too distant future.
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