Can You Really Trust a Skin Biopsy?

When a leading pathologist and author received two very different diagnoses for a skin lesion, she knew that there was a problem with the melanoma classifications system. For Joann Elmore, MD, MPH, a professor of medicine at University of Washington School of Medicine, the experience prompted her to study the rate of contrasting skin lesion interpretations. Her efforts to get to the bottom of “gray area” diagnoses were recently published in The BMJ.

Elmore and her colleagues gathered 240 different skin biopsies, varying from conventional moles to high-stage melanoma. They sent packages of 36 or 48 slides to 187 different pathologists across the country, who were asked to review each slide twice at intervals that were at least eight months apart. The researchers then compared the participating pathologists against their own analyses and the “gold standard” consensus diagnosis that had been determined for each slide by a committee of pathology experts.

They found that overall, pathologists were in agreement on biopsies that fell on opposing sides of the spectrum. However, lesions that were considered to be in the gray area received analyses that were all over the board. In middle-ground cases, the pathologists agreed with the consensus less than half the time, with the agreement rate ranging from 25 to 43 percent. However, the rate in which they agreed with each other was slightly higher, from 35 to 63 percent. In one slide of a mole, 36 pathologists had 18 different diagnoses, their interpretations ranged from common mole to invasive and heavily pigmented melanoma.

“We need to acknowledge and share with our patients that the practice of medicine is, at times, inherently uncertain, wrote Elmore in a post for The BMJ’s blog. “We have oversold our medical capabilities, leading patients to believe (and physicians to hope) that diagnoses can be clearly binary (i.e. either you have the disease or you don’t). We need to acknowledge that vast gray areas often exist.”