A biopsy can tell doctors a great deal about a skin lesion, but the diagnosis still depends on what a pathologist sees under the microscope. In many cases, the answer is clear. In others, particularly with certain melanocytic lesions, there’s more room for interpretation.
Dr. Michael Piepkorn, a clinical dermatologist and dermatopathologist, has spent much of his career studying what happens in those less certain cases. His research has looked closely at reproducibility — how often pathologists examining the same tissue reach the same diagnosis — and where that consistency begins to break down.
Why the Same Slide Can Read Two Different Ways
Interpreting a melanocytic lesion isn’t like reading a number from a lab report. A dermatopathologist looks at cell shape, arrangement, depth, and other microscopic features, then considers how those findings fit within established diagnostic categories. Sometimes they fit neatly. Sometimes they don’t.
Dr. Michael Piepkorn has studied the differences that can emerge in those cases. Research has shown that two pathologists reviewing the same biopsy independently may reach different conclusions. Even the same pathologist may interpret a slide differently when seeing it again without knowing the original diagnosis.
That variability is particularly important when a lesion falls somewhere between clearly benign and clearly malignant. The pathologist is working from established criteria, but applying those criteria still requires professional judgment. In the gray areas, reasonable differences in interpretation can follow.
A Specific Number Behind a General Concern
Research involving Michael Piepkorn, MD, offers a useful example. In a study published in JAAD International, Piepkorn and his coworkers looked at the diagnosis of a moderately dysplastic nevus and found less than 50 percent agreement among independent pathologists reviewing the same case.
Differences also appeared when individual pathologists were shown the same biopsy slide again without being told how they had diagnosed it the first time. In some cases, their second interpretation changed.
That’s especially relevant because moderately dysplastic nevus isn’t a diagnosis limited to a handful of highly unusual cases. It’s encountered in dermatology practice, which means questions about reproducibility can come up in routine patient care.
What Diagnostic Disagreement Can Mean for a Patient
A difference in interpretation can change what happens next. A more conservative diagnosis may lead to observation or limited follow-up. A more concerning diagnosis may lead to additional treatment, procedures, expense, and anxiety.
Knowing how reproducible a diagnosis tends to be gives clinicians another piece of information to consider. Some diagnoses produce a high level of agreement among pathologists. Others are more likely to fall into areas where interpretations differ.
Piepkorn’s research on melanocytic lesion diagnosis has explored that variability and how well it is understood in clinical practice. If a particular diagnosis is known to have lower reproducibility, that may be useful to know before making decisions based on a single pathology report.
Where the Gray Zone Is Widest
Not every case presents the same level of difficulty. A clearly benign common nevus sits at one end of the spectrum, while a well-developed, unambiguous melanoma sits at the other. The harder cases are often the ones in between.
Those lesions may have features that don’t fit comfortably into one category. That’s where professional judgment becomes more important and where disagreement among pathologists can be more common. Through ongoing work in dermatopathology, Piepkorn has continued to examine what happens within this diagnostic gray zone.
For a treating clinician, knowing that a case falls into an area where reproducibility is limited can affect how much weight to place on a single interpretation. Depending on the diagnosis and the treatment being considered, an independent second opinion may provide useful additional information.
Biopsy and pathology remain essential tools in diagnosing melanocytic lesions. Piepkorn’s research adds context to the results they provide by looking at how consistently those results can be reproduced.
For patients, the question can be fairly simple. If a diagnosis falls into an area where pathologists are known to disagree, it may be worth asking whether another review would help before deciding what comes next.
