Pathologists' agreement on treatment suggestions for melanocytic skin lesions

Diagnostic utility of combining PRAME and HMB-45 stains in primary melanocytic tumors

BACKGROUND

Pathologists face ongoing challenges distinguishing between benign and malignant melanocytic tumors. PRAME (PReferentially expressed Antigen in Melanoma) has a demonstrated value distinguishing between these types of lesions. However, the sensitivity of single immunohistochemistry is variable. HMB-45 is another valuable marker, but on its own, has a limited ability in setting of primary melanocytic tumors. This study sought to evaluate the diagnostic potential of a dual panel combining PRAME and HMB-45 in the assessment of primary melanocytic tumors.

METHODS

259 tumors, of which 141 were benign nevi, 31 dysplastic nevi (either low- or high grade dysplasia), and further 87 malignant melanomas, were retrieved from the department's archives and assessed by two experienced dermatopathologists. New sections were stained with PRAME and HMB-45, respectively. For PRAME, a nuclear, and for HMB-45, a cytoplasmic staining, was considered positive and scored as described in the literature on a scale from 0 to 4+. Only dermal component was assessed on HMB-45 stain.

RESULTS

PRAME was diffusely expressed in only 1 benign nevus, with focal expression in further 28 compared to 22 diffusely and 103 focally HMB-45-positive benign nevi. 5 high-grade dysplastic nevi showed diffuse PRAME expression in epidermal component, with varying degree of positivity in adjacent dermal compartment, and further 8 dysplastic nevi showed only focal expression. HMB-45 was diffusely expressed in only 2, with focal expression in 23, and no apparent positivity in remaining 6 dysplastic nevi. In invasive melanoma group, PRAME stained >75 % cells in 64/87 tumors, however, 10/87 melanomas were completely negative. HMB-45 was captured diffusely in 49/87 melanomas, 32 showed patchy expression, and 6 tumors were blank negative. Diffuse 4+ PRAME positivity showed superior sensitivity and specificity of 73,6 % and 96,5 %, respectively, compared to HMB-45, 56,3 % and 86,0 %, respectively. No nevi showed double 4+ positivity, however, the sensitivity for double positivity was only 49,4 %.

CONCLUSION

Our results confirm the superiority of PRAME over HMB-45 in the differential diagnosis of melanocytic tumors. However, combined staining can significantly increase specificity, rendering a benign diagnosis more unlikely in a double 4+ diffuse positivity setting.

Diagnostic error, uncertainty, and overdiagnosis in melanoma

Diagnostic error can be defined as deviation from a gold standard diagnosis, typically defined in terms of expert opinion, although sometimes in terms of unexpected events that might occur in follow-up (such as progression and death from disease). Although diagnostic error does exist for melanoma, deviations from gold standard diagnosis, certainly among appropriately trained and experienced practitioners, are likely to be the result of uncertainty and lack of specific criteria, and differences of opinion, rather than lack of diagnostic skills. In this review, the concept of diagnostic error will be considered in relation to diagnostic uncertainty, and the concept of overdiagnosis in melanoma will be presented and discussed.

Assessing comfort level with pediatric skin specimens among dermatopathologists and pediatric pathologists: A national cross-sectional survey

BACKGROUND

Cutaneous histopathologic diagnoses in children often differ from those in adults. Depending on practice setting, these specimens may be evaluated by dermatopathologists or pediatric pathologists. We sought to determine whether comfort level with pediatric dermatopathology is associated with prior training, pediatric dermatopathology exposure during fellowship, career duration, or specimen subtype.

METHODS

We surveyed dermatopathologists and pediatric pathologists practicing in the United States. Training and practice variables were evaluated by multivariable regression for association with comfort level.

RESULTS

Of the 156 respondents, 72% were dermatopathologists (response rate 11.6%) and 28% were pediatric pathologists (response rate 9.3%). Dermatopathologists reported higher comfort overall (P < .001); this was also true for inflammatory dermatoses and melanocytic neoplasms (P < .001). Thirty-four percent and 75% of dermatopathologists and pediatric pathologists, respectively, reported lower comfort with pediatric skin specimens than their usual cases. Pediatric pathologists were 28% more likely to refer these cases to colleagues. Among dermatopathologists, dermatology-trained were more comfortable than pathology-trained colleagues interpreting inflammatory dermatoses (P < .001).

CONCLUSIONS

Pathologists' comfort with pediatric dermatopathology varied significantly based upon prior training, career duration, and specimen subtype. These results suggest opportunities for improving education in this domain.

ESP, EORTC, and EURACAN Expert Opinion: practical recommendations for the pathological diagnosis and clinical management of intermediate melanocytic tumors and rare related melanoma variants

The recent WHO classification of skin tumors has underscored the importance of acknowledging intermediate grade melanocytic proliferations. A multistep acquisition of oncogenic events drives the progressive transformation of nevi into melanomas. The various pathways described are modulated by the initial oncogenic drivers that define the common, blue, and Spitz nevi groups. Intermediate lesions are most often the result of a clonal evolution within such nevi. Based on this established classification, we have suggested for each pathway a practical diagnostic approach, benefiting from the recently developed molecular tools, both in the setting of general pathology labs and expert centers. Moreover, recommendations regarding the re-excision and clinical follow-up are given to support decision-making in multidisciplinary tumor boards.