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The Importance of Population-Based Estimates of Melanocytic Pathology.

In this issue of JAMA Dermatology, Lott et al1 describe a novel and innovative approach to estimating the prevalence of different types of melanocytic lesions in all adults undergoing skin biopsies in a population. Using an automated natural language processing tool, they analyzed 80 368 written pathology reports of skin biopsies from 47 529 adult patients drawn from an underlying health system patient population, which was representative of the general adult population. For analysis of each pathology report, the diagnosis was first dichotomized as either a melanocytic or nonmelanocytic lesion. For melanocytic lesions, the cases were then assigned to 1 of 4 diagnostic categories based on the Melanocytic Pathology Assessment Tool and Hierarchy for Diagnosis (MPATH-Dx),2 with differing management implications: class I, benign lesion requiring no further treatment; class II, low-risk lesion requiring complete excision with narrow (<5mm) margins; class III, higher-risk lesion such as melanoma in situ requiring reexcision with 5-mm to 1-cm margins; and class IV/V, invasive melanoma requiring wide reexcision with 1-cm margins or greater. Approximately one-quarter of all skin biopsies were of melanocytic lesions. Of these, over 90% were benign or low risk (class I or II); 4.5% were melanoma in situ or similar-risk lesion (class III); and 4.1% were invasive melanoma (class IV/V). Lott et al1 demonstrated how technological advances in text analytical tools provide opportunities to harvest important epidemiological, clinical, and pathologic data on a range of different medical conditions by analyzing pathology reports. Previously, researchers had to manually read, interpret, and annotate pathology reports to determine the appropriate diagnostic category. Automated processes, such as the natural language processing tool used by Lott et al, enable a much larger number of cases to be analyzed and assigned with high accuracy. The generated data are important for demonstrating the relative prevalence and incidence of different medical conditions. The data also allow estimation of the number needed to biopsy (NNB), calculated as the number of melanocytic lesions biopsied for every confirmed melanoma, and this is similar to the number needed to excise, which is considered an important quality measure for melanoma detection.3 Lott et al1 report that invasive melanomas (MPATH-Dx class IV/V) were identified in 4.1% of the individuals undergoing skin biopsies of melanocytic proliferations, giving an NNB of 25. If we include melanoma in situ or similar-risk lesions in addition to invasive melanomas in the calculations (classes III-V), then an estimated 8.6% of melanocytic proliferations were identified as malignant, or an NNB of 12. These rates are comparable to those found in the SCREEN project (Skin Cancer Research to Provide Evidence for Effectiveness of Screening in Northern Germany),4 which found an overall NNB of 17 where biopsy was performed for clinical suspicion of melanoma, and an NNB of 28 for all biopsies regardless of suspicion of melanoma. This suggests that widespread screening for melanoma in the United States general adult population may already be occurring despite the recently updated US Preventive Services Task Force recommendation statement that there is insufficient evidence to recommend for or against this.5 The epidemiological data generated from analyses similar to those performed by Lott el al1 may also be used to help interpret the population impact of findings from non–populationbased studies. For example, a recent study by the same research team examined the reproducibility of pathologists’ interpretations of melanocytic proliferations.6 In that study, pathology cases were deliberately enriched with MPATH-Dx class III to V lesions to ensure accuracy of the interrater agreement estimates for these less frequent pathology classes. Using data from the present study, the researchers were able to reweight the prevalence of skin biopsy classifications in the reproducibility analysis to determine estimates at the population level and the probability that a pathologist’s interpretation of a skin biopsy would be confirmed if reviewed by a panel of experienced dermatopathologists interpreting the same slide. When the reproducibility study data were considered alone, “undercalling” of melanoma histopathology appeared to be much more of a problem than “overcalling” (see Table for definitions). Of patients with an initial pathology diagnosis of an MPATH-Dx class I or II lesion (benign or low-risk lesion), 44.8% would be reclassified upward to a class III, IV, or V lesion on review by a panel of experienced dermatopathologists (ie, melanoma had originally been undercalled). In contrast, of patients with an initial pathology diagnosis of a class III, IV, or V lesion (in situ melanoma, severely dysplastic nevus, or invasive melanoma), 3.7% were reclassified downward to a class I or II lesion (benign or low-risk lesion) on review (ie, melanoma had originally been overcalled) (Table). However, after reweighting for the prevalences found in the general population, the relative rates of overcalling and undercalling reversed. In the general adult population setting, of patients with an initial pathology diagnosis of an MPATH-Dx Related article Opinion