Dermatopathologists May Perpetuate Melanoma Overdiagnosis, Despite Awareness

By Marilynn Larkin

April 29, 2022

NEW YORK (Reuters Health) - Many dermatopathologists think atypical nevi, melanoma in situ and invasive melanoma are overdiagnosed, but awareness does not seem to change their behavior, a survey study found.

"Overdiagnosis of diseases such as melanoma is a complicated problem and probably won't have a simple solution," Dr. Kathleen Kerr of the University of Washington in Seattle told Reuters Health by email. "An interesting finding in our research is that a majority of dermatopathologists agree that they see cases in their practice that should not have been biopsied in the first place."

"While it isn't entirely clear why they think this, it suggests that overdiagnosis may originate with primary care doctors and dermatologists performing too many skin biopsies," she said. "Pathologists overcalling cases then compounds the problem."

"As a biostatistician, I find the evidence for melanoma overdiagnosis very compelling," she added. "Population-level data show that melanoma diagnoses have increased dramatically while melanoma mortality has remained nearly constant over a period with no major advances in treatment."

"Therefore, I was surprised that only one-third of dermatopathologists in our study agreed that invasive melanoma is overdiagnosed," she said. "That means that most are either not aware of the evidence or unconvinced."

As reported in JAMA Dermatology, Dr. Kerr and colleagues surveyed 115 board-certified and/or fellowship-trained dermatopathologists and sought each participant's diagnostic interpretations on one set of 18 skin biopsy cases (out of five slide sets with a total of 90 melanocytic skin lesions). Participants interpreted cases remotely using their own microscopes.

The main survey outcomes were agreement or disagreement that overdiagnosis is a public health issue for atypical nevi, melanoma in situ, and invasive melanoma, as well as associations between perceptions of overdiagnosis and interpretive behavior on study cases.

Sixty-eight percent of those surveyed agreed that overdiagnosis is a public health issue for atypical nevi; 47% for melanoma in situ; and 35% for invasive melanoma.

Those with more years in practice were significantly less likely to perceive that atypical nevi are overdiagnosed compared with less-experienced dermatopathologists: for example, 46% of dermatopathologists with 20 or more years of experience agreed that atypical nevi are overdiagnosed versus 93% of those with 1-4 years of experience.

Compared with other dermatopathologists, those who agreed that all three conditions are overdiagnosed were slightly more likely to diagnose study cases as mild to moderately dysplastic nevi (odds ratio, 1.26), but the difference was not statistically significant.

Dermatopathologists who agreed that invasive melanoma is overdiagnosed did not significantly differ in diagnosing invasive melanoma versus those who disagreed (OR, 1.10). Summing up, the authors state, "In this survey study, about two-thirds of dermatopathologists thought that atypical nevi are overdiagnosed, half thought that melanoma in situ is overdiagnosed, and one-third thought that invasive melanoma is overdiagnosed. No statistically significant associations were found between perceptions about overdiagnosis and interpretive behavior when diagnosing skin biopsy cases."

Dr. John Barbieri of Brigham and Women's Hospital in Boston, associate editor of JAMA Dermatology, commented in an email to Reuters Health. "The findings are not unexpected based on prior work, including some from this same group, highlighting inter- and intra-rater inconsistency with the histologic diagnosis of melanoma."

"Ultimately, a fundamental challenge is that we have no gold standard diagnostic test for melanoma," he noted. "Whether something is a cancer or not is defined by behavior over time, yet pathologists must make this determination with only a static piece of tissue."

"Whether or not you believe overdiagnosis is occurring, the difficulty distinguishing some benign nevi from some melanomas on histopathologic evaluation will inherently favor overdiagnosis out of caution of missing a melanoma," he said. "To solve this issue, we need more research on how to identify whether a skin lesion represents a melanoma or a benign mole."

"In addition, we should be thoughtful about what lesions we biopsy and how we approach population screening," Dr. Barbieri concluded.

SOURCE: JAMA Dermatology, online April 20, 2022.