Discordance Among Expert Pathologists in the Diagnosis of Melanocytic Neoplasms, Histopathologic Diagnosis of Melanoma at a Melanoma Referral Center, and Histopathologic Parameters in Cutaneous Melanoma

This online-only bonus feature is an ongoing review of past peer reveiw journal articles with significant impact on dermatology.

Sean mcGregorSean McGregor, DO, PharmD

Discordance Among Expert Pathologists in the Diagnosis of Melanocytic Neoplasms

The ability of a diagnostic test to produce a diagnosis is predicated upon the reproducibility of that test. Unlike tests that can be quantified with numerical results, a histologic diagnosis is the result of visual analysis and subjective in nature. As a result, considerable variation with regard to individual interpretations of a histologic diagnosis is possible.

In 1991, a panel of expert pathologists and dermatopathologists met for the National Institutes of Health Consensus Development Conference to review melanoma and melanocytic nevi specimens. The goal of the conference was to develop criteria for the diagnosis and the histopathologic features of melanocytic neoplasms. Panel members were asked to submit five “classic cases” of melanoma or melanocytic nevi with shared histologic features. A total of 35 cases and 2 additional cases from the planning committee were then selected, randomized, and sent to the individual panel members for review. The specimens were reviewed and sent back to the planning committee. They were then sent to the next panel member, so everyone reviewed the same slides. Each member was required to determine a diagnosis, whether the specimen was benign, malignant, or indeterminate, and provide criteria for that diagnosis. Prior to the conference, the panel members did not know each other’s diagnosis. Ultimately, there was some variability in the nomenclature of the final diagnosis made by each reviewer.

For example, malignant melanoma in situ, lentigo maligna, junctional lentiginous nevus with atypia, and other such diagnoses were made for a single specimen based on the panel member reviewing the slide. Discordance was then much easier to determine based on the benign, malignant, or indeterminate designations. Complete agreement was achieved in 35% of cases and two or more discordant results were seen in 38% of cases. Overall, there was a moderate level of agreement among the panel members.

The results of this study highlight the interobserver variability among experts in the field with regard to the specific diagnosis and behavior of melanocytic neoplasms. Bernard Ackerman discussed these results in an editorial after the original publication in Human Pathology. Based on the above data, he stated that, “it is obvious…[the experts] did not agree with one another most of the time.” Indeed, there was a lack of consensus regarding the criteria for the diagnosis of melanocytic neoplasms.

References

Farmer ER, Gonin R, Hanna MP. Discordance in the histopathologic diagnosis of melanoma and melanocytic nevi between expert pathologists. Hum Pathol. 1996 Jun;27(6):528-31.

Ackerman AB. Discordance among expert pathologists in diagnosis of melanocytic neoplasms. Hum Pathol. 1996 Nov;27(11):1115-6. 

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