PRAME is a useful marker for the differential diagnosis of melanocytic tumours and histological mimics

AIMS

Although the morphological assessment of melanoma is generally straightforward, diagnosis can be especially difficult when the significant morphological and immunohistochemical results overlap with those of benign and malignant melanocytic tumours and histological mimics. This study assessed the potential diagnostic utility of measuring PReferentially expressed Antigen in MElanoma (PRAME) immunohistochemically in naevi, melanomas and clear cell sarcomas (CCSs) in Chinese patients.

METHODS

We examined the immunohistochemical expression of PRAME in 317 melanocytic naevi, 178 primary melanomas, 72 metastatic melanomas and 19 CCSs and compared the sensitivity and specificity of PRAME immunohistochemistry (IHC) in the differential diagnosis of melanocytic tumours and histological mimics.

RESULTS

Of the 317 melanocytic naevi, 98.1%were completely negative for PRAME; six cases showed focal PRAME immunoreactivity in a minor population of lesional melanocytes. Diffuse nuclear immunoreactivity for PRAME was found in 89.9% of primary melanomas and 93.1% of metastatic melanomas. Regarding melanoma subtypes, PRAME was expressed in 100% of superficial spreading melanomas, 100% of melanomas arise in congenital naevus, 91.4% of nodular melanomas, 87.8% of acral lentigo melanomas, 80.0% of lentigo malignant melanomas, 60.0% of Spitz melanomas, 96.2% of mucosal melanomas and 80.0% of uveal melanomas. None of the two desmoplastic melanomas expressed PRAME. Of the 19 CCS cases, 89.5% were negative for PRAME and 10.5% showed focal weak PRAME immunoreactivity in a minor population of tumour cells.

CONCLUSIONS

Our findings indicate that PRAME may be a useful marker to support a suspected diagnosis of melanoma. In addition, lack of PRAME expression is a valuable hint to CCS in a suspected case, and then molecular confirmation of the presence of EWSR1 rearrangement is necessary.

Ultra-high-frequency ultrasound and machine learning approaches for the differential diagnosis of melanocytic lesions

Malignant melanoma (MM) is one of the most dangerous skin cancers. The aim of this study was to present a potential new method for the differential diagnosis of MM from melanocytic naevi (MN). We examined 20 MM and 19 MN with a new ultra-high-frequency ultrasound (UHFUS) equipped with a 70 MHz linear probe. Ultrasonographic images were processed for calculating 8 morphological parameters (area, perimeter, circularity, area ratio, standard deviation of normalized radial range, roughness index, overlap ratio and normalized residual mean square value) and 122 texture parameters. Colour Doppler images were used to evaluate the vascularization. Features reduction was implemented by means of principal component analysis (PCA), and 23 classification algorithms were tested on the reduced features using histological response as ground-truth. Best results were obtained using only the first component of the PCA and the weighted k-nearest neighbour classifier; this combination led to an accuracy of 76.9%, area under the ROC curve of 83%, sensitivity of 84% and specificity of 70%. The histological analysis still remains the gold-standard, but the UHFUS images processing using a machine learning approach could represent a new non-invasive approach.

Cross-sectional study of pigmented lesions of the head and neck in adults aged 40 years and above

The diagnosis of junctional and lentiginous naevi on sun-damaged skin of the head and neck in adults has been questioned in the literature, with the implication that these lesions should be classified as melanoma in situ. This could result in the overdiagnosis and overtreatment of non-malignant lesions. We conducted a cross-sectional study of the histopathological diagnosis of pigmented lesions biopsied from the head and neck of adults ≥40 years of age that were submitted to a large, Queensland-based pathology centre over seven months. Out of 543 lesions assessed, 293 (54.0%) were flat and 250 (46.0%) were raised. Flat naevi consisted of junctional/lentiginous and compound naevi, either with or without dysplasia. Collectively, flat naevi had a prevalence slightly less than that of melanoma (15.0% versus 19.0% among flat lesions, respectively, and 8.1% versus 11.2% among all lesions, respectively). The mean age of biopsy for all junctional/lentiginous naevi was significantly greater than that of all compound naevi (65.0 years versus 52.2 years; P = 0.001). Junctional/lentiginous naevi were significantly more associated with the neck than intradermal naevi (P < 0.001). In conclusion, benign, flat naevi account for a significant proportion of head and neck lesions in adults ≥40 years of age, and their location alone should not outweigh their histopathology when reaching a diagnosis.

Massively parallel sequencing analysis of benign melanocytic naevi

AIMS

Melanocytic naevi are benign lesions of the skin or mucosa that may constitute non-obligate precursors of malignant melanoma, particularly when they show lentiginous and dysplastic features. The aim of this study was to investigate the repertoire of somatic genetic alterations in melanocytic naevi.

METHODS AND RESULTS

DNA extracted from 12 melanocytic naevi and DNA from matching normal tissue were separately microdissected and subjected to targeted massively parallel sequencing of ≥300 cancer genes. A median of 5.5 (range 1-12) non-synonymous somatic mutations were detected, with 10 cases harbouring mutually exclusive BRAF V600E (6/12) or NRAS (4/12) clonal hotspot mutations. One of the two cases lacking BRAF and NRAS mutations was a dysplastic naevus harbouring an HRAS Q61L hotspot mutation. Analysis of the laser-capture microdissected components of a naevus synchronously diagnosed with in-situ and invasive malignant melanoma revealed a truncal, clonal BRAF V600E mutation, and the acquisition of a CDKN2A homozygous deletion in the invasive component, in conjunction with additional clonal mutations affecting NF2, FAT4 and KDR in both in-situ and invasive malignant components.

CONCLUSION

Melanocytic naevi harbour recurrent BRAF V600E or NRAS hotspot mutations with low mutational burdens. Our findings also show that progression from naevi to malignant melanoma may be driven by the acquisition of additional genetic alterations, including CDKN2A homozygous deletions.

'Mind your Moles' study: protocol of a prospective cohort study of melanocytic naevi

INTRODUCTION

Having many melanocytic naevi or 'moles' on the skin is the strongest predictor of melanoma; thus, much can be learnt from investigating naevi in the general population. We aim to improve the understanding of the epidemiology and biology of naevi by conducting a 3-year prospective study of melanocytic naevi in adults.

METHODS AND ANALYSIS

This is a population-based cohort study of melanocytic naevi in 200 adults aged 20-69 years recruited via the Australian electoral roll. At baseline, participants will complete a questionnaire on their sun behaviour and health and undergo a clinical examination. Three-dimensional (3D) total-body photography will be used to record the images of skin lesions. Pigmented naevi will be analysed in terms of number, diameter, colour and border irregularity using automated analysis software (excluding scalp, beneath underwear and soles of feet). All naevi ≥5 mm will be recorded using the integrated dermoscopy photographic system. A saliva sample will be obtained at baseline for genomic DNA analysis of pigmentation, naevus and melanoma-associated genes using the Illumina HumanCoreExome platform. The sun behaviour and health follow-up questionnaire, clinical examination and 3D total-body photography will be repeated every 6 months for 3 years. The first 50 participants will also undergo manual counts of naevi ≥2 mm and ≥5 mm at baseline, 6-month and 12-month follow-ups. Microbiopsy and excision of naevi of research interest is planned to commence at the 18-month time point among those who agree to donate samples for detailed histopathological and molecular assessment.

ETHICS AND DISSEMINATION

This study was approved by the Metro South Health Human Research Ethics Committee in April 2016 (approval number: HREC/16/QPAH/125). The findings will be disseminated through peer-reviewed and non-peer-reviewed publications and presentations at conferences.

An observational case series on dermatoscopic patterns of fading melanocytic naevi

BACKGROUND/OBJECTIVES

The prevalence of melanocytic naevi falls with age. It has been postulated that this could be due to spontaneous involution (fading). Our objective was to provide dermatoscopic evidence of fading naevi and to describe the patterns of fading observed.

METHODS

Serial dermatoscopic images of naevi demonstrating fading were collected from a set of 25 000 images. Any naevi that showed significant fading, as compared to previous imaging of the same lesion, were included in the analysis.

RESULTS

A total of 47 naevi in 21 patients were found to have significantly faded over a span of 2-11 years. The dermatoscopic fading was observed to occur in two patterns. The most common pattern observed was generalised fading (n = 45), where fading was present over all the naevus. There were two cases of focal fading (n = 2) where fading was present only over one area of the naevus.

CONCLUSIONS

Fading melanocytic naevi are uncommon. Melanocytic naevi fade in recognisable patterns, with generalised fading most commonly observed in our series.

Pigmented naevi and sun protection behaviour among primary and secondary school students in an Eastern Hungarian city

BACKGROUND

The most important risk factors for malignant melanoma are skin type I or II, large number of atypical naevi and a history of sunburn in childhood and adolescence.

METHODS

A cross-sectional study was performed to assess skin type, number of pigmented lesions and sun protection behaviour in 1157 12- to 19-year-old Hungarian students at 20 primary and secondary schools in Debrecen, Hungary. After receiving dermatological training, 18 school doctors examined the students' skin. A questionnaire was completed by the students with the assistance of their parents about sun protection, sunburns and the use of sunbed. Data from 612 questionnaires were evaluated.

RESULTS

Based on the doctors' evaluation, most of the pupils were classified as having skin type II and majority of them had 5-20 naevi, particularly on the trunk. Based on the student's response, 5.2% purposely sunbathed daily, 10.1% did not use any form of sun protection, 32.2% wore sun-protective clothing and 65.7% applied sunscreen generally. 6.9% used sunbed, and 74.0% previously experienced serious sunburn at least once. Indoor tanning statistically correlated with the number of melanocytic naevi.

CONCLUSION

A high prevalence of sunburn was reported by the students and some of them did not apply any sun protection methods but used sunbed at a critical age for developing melanoma at a later time. These data highlight the importance of educating children and parents about appropriate sun protection.

High-definition optical coherence tomography of melanocytic skin lesions

High-definition optical coherence tomography (HD-OCT) scanners have recently been developed. We assessed micromorphological HD-OCT correlates of benign naevi (BN) and malignant melanoma (MM). 28 BN and 20 MM were studied using HD-OCT and histology. Epidermal honeycomb/cobblestone pattern, regular junctional cell nests, and edged papillae are more often observed in BN, whereas fusion of rete ridges, pagetoid cells and junctional and/or dermal nests with atypical cells are more frequently seen in MM. A high overlap of HD-OCT features in BN and MM was observed and in 20% of MM we did not find evidence for malignancy in OCT images at all. Using HD-OCT it is possible to visualize architectural and cellular alterations of melanocytic skin lesions. The overlap of HD-OCT features seen in BN and MM and the absence of suspicious HD-OCT features in some MM represents an important limitation of HD-OCT affecting the sensitivity of HD-OCT in diagnosing MM. High-definition optical coherence tomography and the corresponding vertically sectioned histology of a compound naevus.