Histologic outcomes of excised moderate and severe dysplastic nevi

Dysplastic nevus part II: Dysplastic nevi: Molecular/genetic profiles and management

Dermatologists frequently see patients with clinically atypical nevi and dermatopathologists interpret histologically dysplastic nevi on a near-daily basis, but there is great variability in the definition and management of such lesions. This part of the CME review focuses on information published since the previous comprehensive review (2012), with emphasis on molecular and genetic attributes of histologically dysplastic nevi and clinical management.

Surgical re-excision vs. observation for histologically dysplastic naevi: a systematic review of associated clinical outcomes

BACKGROUND

The management of histologically dysplastic naevi (HDN) with re-excision vs. observation remains controversial because of lack of evidence about associated melanoma outcomes.

OBJECTIVES

To assess published data on the development of biopsy-site primary cutaneous melanoma among biopsy-proven HDN managed with either re-excision or observation.

METHODS

A systematic review of all published data: a total of 5293 records were screened, 18 articles were assessed in full text and 12 studies met inclusion criteria. No controlled trials were identified.

RESULTS

Most studies (11 of 12, 92%) were retrospective chart reviews, and one was both a cross-sectional and cohort study. Many studies (nine of 12, 75%) had no head-to-head comparison groups and either only reported HDN that were re-excised or observed. A total of 2673 (1535 observed vs. 1138 re-excised) HDN of various grades were included. Follow-up varied between 2 weeks and 30 years. Nine studies reported that no melanomas developed. Eleven biopsy-site melanomas developed across three of the studies, six among observed lesions (0·39%) and five among re-excised lesions (0·44%).

CONCLUSIONS

Based upon the available evidence the rates of biopsy-site primary melanoma were similarly low among observed lesions and re-excised lesions. This suggests that HDNs can be observed with minimal adverse melanoma-associated outcomes. However, all included articles were of low quality and further prospective trials could better guide clinical decision making.

Diagnostic Accuracy of Virtual Pathology vs Traditional Microscopy in a Large Dermatopathology Study

Importance

Digital pathology represents a transformative technology that impacts dermatologists and dermatopathologists from residency to academic and private practice. Two concerns are accuracy of interpretation from whole-slide images (WSI) and effect on workflow. Studies of considerably large series involving single-organ systems are lacking.

Objective

To evaluate whether diagnosis from WSI on a digital microscope is inferior to diagnosis of glass slides from traditional microscopy (TM) in a large cohort of dermatopathology cases with attention on image resolution, specifically eosinophils in inflammatory cases and mitotic figures in melanomas, and to measure the workflow efficiency of WSI compared with TM.

Design, Setting, and Participants

Three dermatopathologists established interobserver ground truth consensus (GTC) diagnosis for 499 previously diagnosed cases proportionally representing the spectrum of diagnoses seen in the laboratory. Cases were distributed to 3 different dermatopathologists who diagnosed by WSI and TM with a minimum 30-day washout between methodologies. Intraobserver WSI/TM diagnoses were compared, followed by interobserver comparison with GTC. Concordance, major discrepancies, and minor discrepancies were calculated and analyzed by paired noninferiority testing. We also measured pathologists' read rates to evaluate workflow efficiency between WSI and TM. This retrospective study was caried out in an independent, national, university-affiliated dermatopathology laboratory.

Main Outcomes and Measures

Intraobserver concordance of diagnoses between WSI and TM methods and interobserver variance from GTC, following College of American Pathology guidelines.

Results

Mean intraobserver concordance between WSI and TM was 94%. Mean interobserver concordance was 94% for WSI and GTC and 94% for TM and GTC. Mean interobserver concordance between WSI, TM, and GTC was 91%. Diagnoses from WSI were noninferior to those from TM. Whole-slide image read rates were commensurate with WSI experience, achieving parity with TM by the most experienced user.

Conclusions and Relevance

Diagnosis from WSI was found equivalent to diagnosis from glass slides using TM in this statistically powerful study of 499 dermatopathology cases. This study supports the viability of WSI for primary diagnosis in the clinical setting.

The management of dysplastic naevi: a survey of Australian dermatologists

BACKGROUND/OBJECTIVES

The management of dysplastic naevi based on histopathological grading is a contentious issue. Comprehensive management guidelines are lacking and the approach taken varies between clinicians. The authors sought to understand how Australian dermatologists approach the management of biopsy-proven dysplastic naevi, and the impact of grading of dysplasia upon this management.

METHODS

In total, 547 Fellows of the Australasian College of Dermatologists were surveyed and 218 responses were collected (40% response rate).

RESULTS

Although all dermatologists surveyed would re-excise an incompletely removed severely dysplastic naevus, opinion was divided over whether to treat such a lesion as an in situ melanoma or a dysplastic naevus, with 55% of respondents using a 5-mm margin and the remainder opting for narrow margin re-excision. When the same lesion was reported to be clear of margins by 1 mm after biopsy and the clinical suspicion for melanoma was high, 44% would re-excise with a 5-mm margin.

CONCLUSIONS

The approach of Australian dermatologists to the management of dysplastic naevi varies between clinicians, reflecting the problems raised by the validity of histopathological grading.

Dysplastic (or Atypical) Nevi Showing Moderate or Severe Atypia With Clear Margins on the Shave Removal Specimens Are Most Likely Completely Excised

BACKGROUND

Dysplastic nevi (DN) are graded by their degree of atypia into 3 categories of mild, moderate, and severe. In many practices, DN with moderate or severe atypia are generally excised regardless of the status of the shave specimen margins.

OBJECTIVE

With a new approach toward the margins on the shave removal specimens (SRS), the goal herein is to assess whether the shave removal procedure can sufficiently remove DN with moderate or severe atypia.

METHODS

A total of 426 SRS diagnosed with DN showing moderate or severe atypia between January and December 2015 along with their post-shave excision specimens were reviewed. Based on the author's experience, clear or negative margins on the SRS were defined as neoplastic melanocytes confined within >0.2 mm of the lateral and deep specimen margins. The biopsy specimens were accompanied by Melan-A highlighting the subtle neoplastic cells.

RESULTS

With a negative predictive value (NPV) of 98.4% (confidence interval: 97.2% to 100%, P < .001), DN showing moderate or severe atypia with clear margins are most likely removed by the shave procedure.

CONCLUSION

Routine excision of DN showing moderate or severe atypia with clear margins on SRS is not necessary. Regular surveillance is sufficient.

Melanoma progression

Tumours progress to fully malignant neoplasms through stages of development in a stepwise process. A carcinogenic stimulus such as UV light typically results in a large number of lesions, most of which are benign. Most such lesions will remain stable or regress, while a few will develop cytological and architectural atypia, placing them in a morphologically 'intermediate' category between wholly benign and fully malignant. It is important to categorise intermediate lesions, as they may be simulants, risk markers, and potential precursors of malignancy. Although many but not all malignancies arise in an evident precursor lesion, the vast majority of 'potential precursors' will not progress, as is evidenced by their vastly greater numbers in populations. Progression continues with the onset of malignancy including in metastatic disease. In melanoma as in other tumours, progression has been clearly related to the stepwise acquisition of genetic abnormalities. The first step is the activation of a single 'driver' oncogene, which is sufficient to induce a benign neoplasm whose growth is limited by oncogene-induced senescence driven by activated suppressors. In the intermediate lesions, additional genetic alterations occur such as additional driver mutations or heterozygous loss of suppressors due to copy number variation or other mechanisms. Fully malignant lesions are characterised by complete loss of relevant suppressors and by additional abnormalities, which together account for attributes of malignancy such as invasion and metastasis. Any of the steps of progression can be 'skipped', potentially due to telescoped progression or to alternative pathways. Although stages of progression might simply be viewed as markers of an individual's risk for developing subsequent stages, genetic associations that have been demonstrated among contiguous stages of progression in complex primary tumours and in their metastases would argue against this. For example, complex primary melanomas can be associated with remnants of earlier stage lesions both clinically and histologically. These include small symmetrical benign naevi and/or morphologically atypical dysplastic naevi ('precursor naevi'), and/or radial growth phase melanomas many of which may be inexorably progressive but lack competence for metastasis. Vertical growth phase is the stage of melanoma progression in which risk for metastasis may be acquired. This risk can be characterised statistically using prognostic attributes which at present are mostly clinicopathological, although in the future molecular profiling may contribute or even supplant these attributes. In metastatic disease, tumours can continue to progress, acquiring resistance to various therapeutic strategies which presents a considerable challenge to the efficacy of current promising therapeutic strategies.

Dysplastic nevus: Fact and fiction

The term "dysplastic nevus" (DN) implies that this nevus exists as a distinct and defined entity of potential detriment to its host. We examine the current data, which suggest that this entity exists as histologically and possibly genetically different from common nevus, with some overlapping features. Studies show that a melanoma associated with a nevus is just as likely to arise in a common nevus as in DN. Furthermore, there is no evidence that a histologically defined DN evolves into a melanoma or that the presence of 1 or more DN on an individual patient confers any increased melanoma risk. We suggest that the term "dysplastic nevus" be abandoned so that the focus can shift to confirmed and relevant indicators of melanoma risk, including high nevus counts and large nevus size.