Can a new classification system help clinicians ID pigmented lesions?

Acta Eruditorum

Abby Van Voorhees

Dr. Van Voorhees is the physician editor of Dermatology World. She interviews the author of a recent study each month.

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In this month’s Acta Eruditorum column, Physician Editor Abby S. Van Voorhees, MD, talks with Michael Piepkorn, MD, PhD, about his recent Journal of the American Academy of Dermatology article, “The MPATH-Dx reporting schema for melanocytic proliferations and melanoma.”

Dr. Van Voorhees: Why create a new reporting classification system for pigmented lesions? Is there discordance in the interpretation of all types of pigmented lesions?

Dr. Piepkorn: No, concordance is generally quite good for stereotypical melanocytic lesions with “textbook” features. An ordinary nevus would engender little if any disagreement. The same holds true for thick primary melanomas. Discordance exists because, simply put, there is an intractable histological “grey zone” between benign and malignant that on occasion cannot be resolved by the present criteria-based process for diagnosis.

Dr. Van Voorhees: How do you define this grey zone?

Dr. Piepkorn: One could define grey zone lesions as those proliferations that share histological features crossing two or more conventional diagnostic categories. Criteria for the diagnostic categories have evolved over a century or more of histological alterations observed by our predecessors in histological sections of melanocytic lesions. Criteria historically tended to derive from stereotypical lesions, which were then extrapolated across the broad spectrum of proliferations encountered in daily practice. Few of the criteria have been rigorously vetted by correlation with the true gold standard, which is disease biology. Criteria are thus often “soft,” namely, there are limitations in their diagnostic sensitivity, specificity, and predictive value. Moreover, application of the criteria to given lesions is often subjective and thus not uniformly reproducible between observers.

Dr. Van Voorhees: What impact has this lack of standardization of nomenclature had?

Dr. Piepkorn: Due to the existence of a histological grey zone in which lesions may have features, to a greater or lesser degree, that overlap more than one conventional diagnostic category, leaders in the field of dermatopathology have tended to develop their own unique lexicon of diagnostic nomenclatures. The range of terminologies reflect personalized viewpoints regarding various aspects of melanocytic neoplasia, among which are histogenetic relationships between lesions and assumptions regarding stages in the putative pathways of neoplastic progression. Much of the range of personalized viewpoints stems from hypothetical arguments and is largely not empirically based. While it is understandable how this evolution in nomenclature evolved, the difficulties occur when recipients of pathology reports become confused by arcane terminology that can predispose to miscommunication, interventions (or lack thereof) that are not indicated, and harm to patients. A standardized reporting scheme, such as we have proposed in the MPATH-Dx algorithms, could potentially lessen miscommunication and errors of omission or commission.

Dr. Van Voorhees: Is the lack of standardization unique to pigmented lesions? Are there things that you learned from other clinical fields that you applied to melanocytic pathology?

Dr. Piepkorn: The lack of standardization is clearly not unique to pigmented lesions but may be somewhat more of an issue in this field due to the complexity and range of the histological alterations compared with some other tumor systems. Our inspiration for MPATH-Dx, in fact, came about in part by our recognition that difficulties with standardization in the field of mammography led to government-mandated reform that eventuated in the BiRads paradigm implemented by the American College of Radiology for reporting of mammogram results. Implementation of that system has resulted in improvements in patient care and reduction in adverse medicolegal events.[pagebreak]

Dr. Van Voorhees: How did you develop the MPATH-Dx histology reporting form? What are its features? How did you categorize the various types of pigmented lesions?

Dr. Piepkorn: The MPATH-Dx histology reporting form developed by necessity when the experienced pigmented lesion pathologists “compared notes” during consensus reviews that followed independent interpretations of over 200 lesions. Basically, we faced substantial differences in interpretation and a confusing breadth of individual terminologies that we recognized as potentially confounding to clinicians and their patients in some situations. Taking inspiration from BiRads, we developed by iterative review a schematic document that attempts to group lesions and their diagnostic nomenclatures by certain global characteristics, namely presumed histogenetic relationships and degree of abnormality under the hypothesis that melanocytic neoplasia is developmental in nature and in part stepwise. In most instances, the three-member panel of experienced melanocytic lesion pathologists could agree on the grouping based on the hypothetical assumptions.

Dr. Van Voorhees: There is also a diagnostic-treatment mapping tool as well, correct? How does this work?

Dr. Piepkorn: The diagnostic-treatment mapping tool seeks to standardize the language pathologists use to assign levels of perceived risk from given melanocytic lesions and their recommendations as to treatment that would be indicated, if any. It is assumed, of course, that standardized language regarding risk and treatment will reduce (although not eliminate) confusion in communication with the clinician and thereby lessen the potential for unintended errors of omission or commission in treatment of the patient. Under these presumptions, the diagnostic-treatment mapping scheme has broad analogies with the reporting form, but it carries the latter one step further by beginning the process of developing standardized language for the risk-treatment algorithms. For each category in the mapping tool there are, accordingly, columns that list the risk-treatment language we propose as a first step in initiating this process of standardization in the field of melanocytic lesion dermatopathology.

Dr. Van Voorhees: Have other dermatopathologists given you feedback on this schema? Have they found it intuitive to work with? Is there any disagreement about some of the categories that you’ve created?

Dr. Piepkorn: We published our proposals in the January issue of the Journal of the American Academy of Dermatology, and it is therefore early in the process. An editorial accompanying our paper by Dirk Elston, MD, did take issue with specific lesions grouped together under some of the headings, which is not surprising considering the diversity of opinions that exist in the field. It is our intent that the schema not be implemented until it has been vetted by professional societies in the field. The process of implementation of schema of these types, if they are to be implemented at all, should include a thorough review of groupings of specific lesions and word crafting of the specific language to be used to attempt standardization of risk assessment and the specific therapy that would be appropriate, if any, for the lesional groupings. 

Dr. Piepkorn is clinical professor of dermatology at the University of Washington School of Medicine. His article appeared in the January 2014 issue of the Journal of the American Academy of Dermatology; J Am Acad Dermatol. 2014;70:131-41. doi:10.1016/j.jaad.2013.07.027