Survey finds ironic aspect of melanoma over-diagnosis

"Over-diagnosis is a really challenging problem because both doctors and patients are wary of missing a cancer, which is understandable," says Kathleen Kerr. (Credit: Getty Images)

Although a survey of pathologists who diagnose melanoma say the skin cancer is over-diagnosed, that view doesn’t affect their behavior, research finds.

As the most serious type of skin cancer, a melanoma diagnosis carries emotional, financial, and medical consequences.

“Over-diagnosis is the diagnosis of disease that will not harm a person in their lifetime. If melanoma is being over-diagnosed, it means that too many people are getting the scary news that they have cancer, and receiving and paying for unnecessary treatment,” says Kathleen Kerr, professor of biostatistics in the University of Washington School of Public Health.

Kerr recently published results of a study involving more than 100 dermatopathologists—pathologists who specialize in skin diseases and who diagnose melanoma—to find out if they believe that melanoma over-diagnosis is a public health issue in the United States and whether that belief affects their own conclusions. The pathologists received biopsy slides to diagnose and took surveys on their perceptions of over-diagnosis.

The National Institutes of Health supported the study, which appears in JAMA Dermatology. Kerr discusses the results here:


How can you know if a disease is being over-diagnosed?


Over-diagnosis is often studied by looking at population-level data rather than individual cases. Melanoma diagnoses have been rising in the US. If there were truly an epidemic of melanoma, we would expect that deaths from melanoma to show a corresponding rise, since there hasn’t been a major breakthrough in treatment during this time. Yet melanoma deaths have been remarkably constant. This suggests that the rise in melanoma diagnoses is largely due to over-diagnosis.


Why does this happen when it comes to melanoma?


The problem is multifaceted. Most of us who aren’t doctors think that if we have something on our skin that could possibly be cancer, and we get it biopsied, then the pathologist’s diagnosis after examining the skin tissue under a microscope is definitive. Reality is more complicated.

Skin abnormalities are some of the most challenging cases for pathologists to diagnose. Previous research has shown that different pathologists who examine the same skin biopsy will sometimes give different diagnoses—to a very surprising degree. The same pathologist examining the same case on two different occasions might even give two substantially different diagnoses.

While advanced melanoma is fairly easy for pathologists to diagnose, difficulties arise for cases where the biopsy shows some kind of abnormality that doesn’t appear to be melanoma but might be a precursor to melanoma. These are the instances where pathologists show the most diagnostic variability, and the cases that raise the possibility of over-diagnosis.


What did find in your study?


The first component of our recent paper was a survey of practicing dermatopathologists’ perceptions about over-diagnosis. About half perceive that noninvasive melanoma is over-diagnosed and one-third perceive that invasive melanoma is over-diagnosed. Also, a majority of dermatopathologists agree that they see cases that should not have been biopsied in the first place. This points to over-diagnosis as a system-wide issue—a problem that may be rooted in too many skin biopsies.

The second component of our study was looking for relationships between pathologists’ perceptions on over-diagnosis and how they diagnosed actual skin biopsies. We thought that those who think invasive melanoma is over-diagnosed might be more reserved in making this diagnosis, but this was not true. In fact, those who think invasive melanoma is over-diagnosed were slightly more likely to diagnose invasive melanoma compared to other dermatopathologists examining the identical cases.


What do you think is the importance of this finding?


Over-diagnosis is a really challenging problem because both doctors and patients are wary of missing a cancer, which is understandable. Our study shows there is widespread recognition of melanoma over-diagnosis among dermatopathologists.

We also show that awareness of over-diagnosis may not be enough to reduce over-diagnosis. It isn’t surprising that such a complicated problem won’t have a simple solution. Reducing over-diagnosis will need to involve patients and primary care doctors having more restraint with obtaining skin biopsies, and pathologists exercising restraint in diagnosing cases as melanoma.