Melanoma on congenital melanocytic nevi.

Among nevus-associated melanomas, which overall account for 20%-30% of all melanomas, those arising specifically in congenital melanocytic nevi are infrequent, but can be disproportionately frequent in childhood and adolescence. Congenital melanocytic nevi (CMNi) are common benign melanocytic tumors that are present at birth or become apparent in early childhood. They are classified based on the projected adult size. Small and medium-sized CMNi are frequent, whereas large/giant CMNi (over 20 cm in diameter) are rare, but can be associated with high morbidity due to marked aesthetic impairment and the risk of neurocutaneous syndrome or melanoma development. In this setting, melanomas can appear in early childhood and are very aggressive, while the risk of small-medium CMNi of developing melanoma is low and similar to non-congenital melanocytic nevi. Histologically, most melanomas on CMNi initiate their growth at the epidermal-dermal junction, but in large/giant CMNi they can develop entirely in the dermis, in deeper tissues, or in extracutaneous sites (especially in the central nervous system). Most CMNi harbour an NRAS mutation, but other genes are rarely involved, and gene translocations have recently been described. However, no prognostic implications have been associated with the CMN genotype. Melanomas developed on CMNi harbour additional molecular alterations to which the aggressive clinical course of these tumors has been attributed. This review covers the distinctive clinical and pathological aspects of melanomas on CMNi, and includes the epidemiology, etiopathogenesis, clinical and dermoscopic presentation, histological and molecular characteristics, as well as tumour behaviour.

Amplification of Mutant NRAS in Melanocytic Tumors With Features of Spitz Tumors.

NRAS activating mutations are prevalent in melanocytic neoplasia, occurring in a subset of common acquired melanocytic nevi and ∼30% of cutaneous melanomas. In this study, we described a cohort of 7 distinctive melanocytic tumors characterized by activating point mutations in codon 61 of NRAS with amplification of the mutant NRAS allele and shared clinicopathologic features. These tumors occurred predominantly in younger patients, with a median age of 20 years (range, 6-56 years). They presented as papules on the helix of the ear (4 cases) or extremities (3 cases). Microscopically, the tumors were cellular, relatively well-circumscribed, compound, or intradermal proliferations. The tumor cells often extended into the deep reticular dermis and involved the superficial subcutaneous fat in some cases. The melanocytes were epithelioid to spindled with moderate amounts of cytoplasm and conspicuous nucleoli. They were arranged in short plexiform fascicles, nests, and cords. Some cases had occasional pleomorphic and multinucleated melanocytes. Rare dermal mitotic figures were present in all cases. The dermis contained thick collagen bundles and minimal solar elastosis. Follow-up data were available for 5 patients, with a median period of 4.2 years (range, 1-9 years), during which no recurrences or metastases were reported. Our series highlights a clinicopathologically and molecularly distinctive subset of NRAS-mutated tumors with amplification of the mutant NRAS allele.

Review: Are moles senescent?

Melanocytic nevi (skin moles) have been regarded as a valuable example of cell senescence occurring in vivo. However, a study of induced nevi in a mouse model reported that the nevi were arrested by cell interactions rather than a cell-autonomous process like senescence, and that size distributions of cell nests within nevi could not be accounted for by a stochastic model of oncogene-induced senescence. Moreover, others reported that some molecular markers used to identify cell senescence in human nevi are also found in melanoma cells-not senescent. It has thus been questioned whether nevi really are senescent, with potential implications for melanoma diagnosis and therapy. Here I review these areas, along with the genetic, biological, and molecular evidence supporting senescence in nevi. In conclusion, there is strong evidence that cells of acquired human benign (banal) nevi are very largely senescent, though some must contain a minor non-senescent cell subpopulation. There is also persuasive evidence that this senescence is primarily induced by dysfunctional telomeres rather than directly oncogene-induced.

Mosaic BRAF Fusions Are a Recurrent Cause of Congenital Melanocytic Nevi Targetable by MAPK Pathway Inhibition.

Among children with multiple congenital melanocytic nevi, 25% have no established genetic cause, of whom many develop a hyperproliferative and severely pruritic phenotype resistant to treatment. Gene fusions have been reported in individual cases of congenital melanocytic nevi. We studied 169 patients with congenital melanocytic nevi in this study, 38 of whom were double wild type for pathogenic NRAS/BRAF variants. Nineteen of these 38 patients had sufficient tissue to undergo RNA sequencing, which revealed mosaic BRAF fusions in 11 of 19 patients and mosaic RAF1 fusions in 1 of 19. Recurrently, fusions involved the loss of the 5´ regulatory domain of BRAF or RAF1 but preserved the kinase domain. We validated all cases and detected the fusions in two separate nevi in 5 of 12 patients, confirming clonality. The absence of the fusion in blood in 8 of 12 patients indicated mosaicism. Primary culture of BRAF-fusion nevus cells from 3 of 12 patients demonstrated highly increased MAPK activation, despite only mildly increased BRAF expression, suggesting additional mechanisms of kinase activation. Trametinib quenched MAPK hyperactivation in vitro, and treatment of two patients caused rapid improvement in bulk tissue, improving bodily movement and reducing inflammation and severe pruritus. These findings offer a genetic diagnosis to an additional group of patients and trametinib as a treatment option for the severe associated phenotypes.

A clinical and biologic review of congenital melanocytic nevi.

Congenital melanocytic nevi (CMN) are the result of aberrations in the mitogen-activated protein kinase signal transduction pathway caused by postzygotic somatic mutations. The estimated incidence of newborns with CMN is 1%-2%. The main complications of CMN include proliferative nodules, melanomas, and neurocutaneous melanosis, and the latter two are the most troublesome issues to address. Treatments are primarily taken into account for aesthetic purposes and the reduction of melanoma risk. Due to the much lower incidence of malignant transformation observed in recent studies than in previous data, clinical management paradigms for CMN patients have gradually shifted towards conservative observation and close monitoring. Surgery and lasers are still the main treatments, and targeted therapy may be a promising strategy to help manage complications. With the increase in awareness of mental health, increasing focus has been placed on the quality of life (QoL) and psychological issues of both CMN patients and their parents. Recent studies have revealed that families coping with CMN might endure intense pressure, a major loss in QoL, and psychological problems after diagnosis and during treatment. Here, we sought to present an overview of genetic basis, complications, treatments, and psychological issues related to CMN and hope to provide better management for patients with CMN.

The Skin Molecular Ecosystem Holds the Key to Nevogenesis and Melanomagenesis.

Early detection of melanoma is critical to good patient outcomes, but we still know little about the mechanisms of early melanoma development. Normal epidermis has many of the sequence variants and genetic architecture disruptions found in both benign nevi, melanomas, and other skin cancers, yet continues to behave more or less normally. One hypothesis is that many melanocytes in this context are "tumor competent" but are regulated by the microenvironment provided by the surrounding keratinocytes to inhibit progress to nevi or melanoma. There is evidence of accumulating disorder in several measures of the genomic and epigenomic landscape from normal skin through nevi to melanoma that may be key to promoting nevogenesis and melanomagenesis.

Clinical, Morphologic, and Molecular Features of Benign and Intermediate-grade Melanocytic Tumors With Activating Mutations in MAP2K1.

Activating mutations in MAP2K1 can be seen in benign and intermediate-grade melanocytic neoplasms with spitzoid morphology. We analyzed the clinical, histopathologic, and genetic features for 16 cases of benign and intermediate-grade melanocytic tumors harboring activating MAP2K1 mutations. We compared them to Spitz neoplasms with characteristic Spitz fusions or HRAS mutation. We also compared the mutational pattern of benign and intermediate-grade MAP2K1 -mutated neoplasms and melanomas with activating MAP2K1 mutations. Among the 16 cases, the favored morphologic diagnosis was Spitz nevus (8/16), atypical Spitz tumors (6/16), and deep penetrating nevus (2/16). The 2 most common architectural patterns seen included a plaque-like silhouette with fibroplasia around the rete reminiscent of a dysplastic nevus (n=7) or a wedge-shaped or nodular pattern with the plexiform arrangement of the nests aggregating around the adnexa or neurovascular bundle (n=8). The cases with dysplastic architecture and spitzoid cytology resembled dysplastic Spitz nevi. Compared with true Spitz neoplasms, MAP2K1 -mutated neoplasms occurred in older age groups and had more frequent pagetosis and a lower average mitotic count. The most common type of mutation in the benign and intermediate-grade cases in the literature involves an in-frame deletion, while, in melanomas, missense mutations are predominant. Benign and intermediate-grade melanocytic neoplasms with activating mutations in MAP2K1 can have morphologic overlap with Spitz neoplasms. A significant proportion of melanomas also have activating MAP2K1 mutations. In-frame deletions are predominantly seen in the benign and intermediate-grade cases, and missense mutations are predominantly seen in melanomas.

Genetic and phenotypic diversities of nevus spilus phenotypes: Case series and a proposed diagnostic algorithm.

Nevus spilus (NS) is composed of multiple types that characterized by a congenital hyperpigmented patch within variable even superimposed lesions originating from melanocytic lineage cells. The molecular mechanism and classification of diverse NS phenotypes remain unclear. Five children with a phenotype of NS were genotyped by the panel based on next-generation sequencing in this study. DNA from biopsies, blood samples and hair follicle were sequenced to confirm the presence of a somatic mutation. Sequencing results indicated somatic mutation in the gene of NRAS or HRAS in all biopsies from the nevi, and the pathogenic variants were not detected in the samples of blood and hair follicle. This study successfully identified the somatic mutation in five unrelated children with diverse NS phenotypes. Moreover, it provided typical images and differential diagnoses between variable NS phenotypes in clinical, pathological, and genetic features, and first proposed a clinical diagnostic algorithm that contributed to simplifying and optimizing the diagnoses and management of these overlapped diseases.

PRAME Immunohistochemical Expression and TERT Promoter Mutational Analysis as Ancillary Diagnostic Tools for Differentiating Proliferative Nodules From Melanoma Arising in Congenital Nevi.

ABSTRACT: Proliferative nodules (PNs) are benign melanocytic proliferations that typically develop within congenital melanocytic nevi. These tumors have overlapping histological features with melanoma. Ancillary immunohistochemistry and genomic sequencing are often used in diagnostically challenging cases. To assess the utility of preferentially expressed antigen in melanoma (PRAME) immunoreactivity and telomerase reverse transcriptase (TERT) promoter mutation analysis in distinguishing PNs from melanoma arising in congenital nevi cases. Twenty-one PNs and 2 melanomas arising in congenital nevi were immunohistochemically stained with PRAME. Cases with adequate tissue were also assessed for TERT promoter mutations through sequencing studies. The positivity rates in the PN cases were compared with those of the melanomas. Two of 21 PN cases were diffusely positive for PRAME (≥75% of the tumor cells positive). Two of 2 melanomas arising in congenital nevus cases were also diffusely PRAME positive. The difference was statistically significant using a Fisher exact test. None of the tumors harbored TERT promoter mutations. PRAME immunohistochemical marker may have diagnostic value in distinguishing diagnostically challenging PNs from melanoma, but diffuse expression is not specific for melanoma.

Ambiguous genitalia, giant congenital melanocytic nevus and subpulmonic outlet ventricular septal defect in an African child with Neurofibromatosis 1.

Neurofibromatosis type 1 is an autosomal dominant multisystemic disease caused by mutation of the neurofibromin (NF1) gene located on chromosome 17q11. We report a case of Neurofibromatosis 1 with ambiguous genitalia, giant congenital melanocytic nevus, and associated subpulmonic outlet ventricular septal defect, hitherto unreported in sub-Saharan Africa. In addition, a literature review of congenital heart diseases associated with Neurofibromatosis 1 is presented.

CircFAT1 Promotes the Proliferation and Invasion of Malignant Melanoma through miR375-SLC7A11 Signal Axis.

BACKGROUND: Circular RNA, as a member of noncoding RNA, plays an important role in the occurrence, development and metastasis of tumor cells. So far, the correlation between circular RNA and malignant melanoma remains obscure. METHODS: RNA expression of circFAT1 and miR-375 in malignant melanoma (MM) tissues and cell lines was detected by RT-PCR. The proliferation, cloning, migration and invasion of SK-Mel-28 and A375 cells were assessed using CCK-8 test, clone formation and Transwell assay, respectively. CircRNA immunoprecipitation was used to validate the relationship between circFAT1 and miR-375. The binding between circFAT1 and miR-375, as well as SLC7A11 and miR-375 were verified by luciferase assay. RESULTS: In our study，the circFAT1 was significantly overexpressed in the MM tissue than melanocytic nevi. Conversely, the expression of miR-375 in MM tissue was lower than in melanocytic nevi tissue. The underexpression of circFAT1 with siRNA plasmids significantly suppressed the proliferation, invasion and clone formation of MM cell line. Mechanistically, circFAT1 positively regulates the expression level of SLC7A11 by sponging miR-375. The promotive effects of circFAT1 on the proliferation and invasion ability of MM cells were reversed by the upregulation of miR-375. CONCLUSION: circFAT1 promotes the proliferation, invasion and clone formation of malignant melanoma cells by improving the expression level of SLC7A11 via sponging miR-375.

The association of BRAF V600E gene mutation with proliferative activity and histopathological characteristics of congenital melanocytic nevi in children.

BACKGROUND: A lot of congenital melanocytic nevi (CMN) carry the somatic mutation in the oncogene BRAF V600E. But the detailed histopathologic characteristics and the proliferative activity of CMN with BRAF V600E gene mutation have not been systematically documented. OBJECTIVE: To identify the proliferative activity and histopathological features correlating them with BRAF V600E gene mutation status in CMN. METHODS: CMN were retrospectively identified from the laboratory reporting system. Mutations were determined by Sanger sequencing. The CMN were divided into a mutant group and control group according to whether there was BRAF gene mutation and were strictly matched according to gender, age, nevus size, and location. Histopathological analysis, analysis of Ki67 expression by immunohistochemistry and laser confocal fluorescence microscopy were performed. RESULTS: The differences in Ki67 index, the depth of nevus cell involvement and the number of nevus cell nests between the mutant group and the control group was statistically significant, with p-values of 0.041, 0.002 and 0.007, respectively. Compared with BRAF V600E negative nevi, BRAF V600E positive nevi often exhibited predominantly nested intraepidermal melanocytes, and larger junctional nests, but the difference in this data sets were not statistically significant. The number of nests (p = 0.001) was positively correlated with the proportion of Ki67 positive cells. STUDY LIMITATIONS: A small sample of patients were included and there was no follow-up. CONCLUSIONS: BRAF V600E gene mutations were associated with high proliferative activity and distinct histopathological features in congenital melanocytic nevi.

PRAME expression by immunohistochemistry and reverse transcription quantitative PCR in conjunctival melanocytic lesions-a comprehensive clinicopathologic study of 202 cases and correlation of cytogenetics with PRAME expression in challenging conjunctival melanocytic lesions.

This study examined PRAME (preferentially expressed antigen in melanoma) expression by immunohistochemistry and reverse transcription quantitative PCR (RT-qPCR) in 202 histologically unequivocal conjunctival melanocytic lesions: 76 nevi, 29 benign melanoses, 25 low-grade conjunctival intraepithelial melanocytic lesions (LGCMIL), 26 high-grade conjunctival melanocytic intraepithelial lesions/in-situ melanoma (HGCMIL), and 46 invasive melanomas. PRAME score 0 was seen in 96% of nevi (73/76), 96% of benign melanoses (28/29), and 88% of LGCMIL (22/25). PRAME score 4 was seen in 50% HGCMIL (13/26) and 76% invasive melanomas (35/46). PRAME score 4 had a sensitivity of 50% and specificity of 100% in differentiating between HGCMIL and benign melanosis/LGCMIL. PRAME score 4 had a sensitivity of 76% and specificity of 100% in differentiating between melanoma and nevi. Relative quantification of PRAME mRNA expression by RT-qPCR was performed on 49 cases (24%): 17 nevi, 3 benign melanoses, 5 LGCMIL, 9 HGCMIL, and 15 invasive melanomas. The analysis generated two distinct groupings with 'high' relative PRAME expression for the HGCMIL and invasive melanoma and 'low/zero' expression for nevi, benign melanosis, and LGCMIL. Thirty-three challenging conjunctival melanocytic lesions that had previous fluorescence in situ hybridization (FISH) analysis were studied: 18 nevi, 12 melanomas in a nevus, 2 nevoid melanomas, and 1 in-situ melanoma. All nevi (100%) showed concordance between negative FISH and PRAME (scores 0-3). Four of 13 melanomas (31%; in-situ, invasive, isolated, and in association with nevus) showed concordance between positive FISH and PRAME score 4. In conclusion, PRAME score 4 has 100% specificity for the diagnosis of HGCMIL and melanoma. PRAME is limited in its sensitivity in the evaluation of challenging melanocytic lesions.

Melanocytic naevi, melanocytomas and emerging concepts.

With the elucidation of the genetics of melanocytic tumours, new concepts have emerged. An important one is the identification of 'intermediate' melanocytic tumours, those with genetic progression events beyond those of melanocytic naevi but that are not fully malignant. Thus, melanocytic tumours exist on a genetic spectrum that likely corresponds to biological behaviour. There are multiple pathways to melanoma development with different initiating events and characteristic benign melanocytic neoplasms and the precise placement of tumours on these pathways remains to be established and the corresponding risks of progression quantified. In this review, I discuss the classification of melanocytic naevi based on clinical, histopathological and genetic features, as well as the concept of melanocytomas with discussion of specific recognisable subtypes.

Phacomatosis spilosebacea: A new name for a distinctive binary genodermatosis.

Phacomatosis pigmentokeratotica (PPK) is defined by the association of papular nevus spilus arranged in a flag-like pattern and sebaceous nevus following Blaschko's lines. A systematic search of the worldwide literature retrieved 95 well-established PPK cases. An additional 30 cases were excluded for a number of reasons. Based on this study, we propose to rename PPK phacomatosis spilosebacea (PSS). Mosaic mutations of the HRAS gene are the only proven cause of PSS. The extracutaneous abnormalities of PSS result from various degrees of intermingling of Schimmelpenning syndrome and papular nevus spilus syndrome. PSS seems to be a condition at particularly high risk of developing basal cell carcinoma, urogenital malignancies, and vitamin D-resistant hypophosphatemic rickets. Extracutaneous abnormalities were detected in approximately 75% of PSS cases.

Association of novel MUC16, MAP3K15 and ABCA1 mutation with giant congenital melanocytic nevus.

BACKGROUND: Giant congenital melanocytic nevus (GCMN) is the benign nevomelanocytic proliferation. Mutations in NRAS have been previously detected in GCMN, but mutations in BRAF are generally lacking in the Chinese population. Mutated genes in this disease can estimate the risk of malignant transformation in GCMN. Therefore, it is worth investigating the genetic information of GCMN. METHODS: Here, we presented two cases of GCMN of the upper extremities. The clinical and histological data were analyzed. The whole exome sequencing (WES) was performed to investigate the mutational profile of peripheral venous blood (PB), normal skin (NS), small melanocytic nevus (SMN), deep penetrating and non-penetrating GCMN (dPGCMN and nPGCMN). RESULTS: We showed a reduction in the circumference of involved upper extremities in both patients. The clinical and histopathological data indicated the reduction of adipose tissue associated with the invasion of GCMN. The WES data revealed that MUC16, MAP3K15 and ABCA1 were novel potential candidate genes for the disease as well as biomarkers for predicting malignant transformation. CONCLUSION: The MUC16, MAP3K15 and ABCA1 may serve as novel biomarkers for predicting malignant transformation and targets for the diagnoses and therapy for the GCMN.

Successful treatment with MEK-inhibitor in a patient with NRAS-related cutaneous skeletal hypophosphatemia syndrome.

Cutaneous skeletal hypophosphatemia syndrome (CSHS) is caused by somatic mosaic NRAS variants and characterized by melanocytic/sebaceous naevi, eye, and brain malformations, and FGF23-mediated hypophosphatemic rickets. The MEK inhibitor Trametinib, acting on the RAS/MAPK pathway, is a candidate for CSHS therapy. A 4-year-old boy with seborrheic nevus, eye choristoma, multiple hamartomas, brain malformation, pleural lymphangioma and chylothorax developed severe hypophosphatemic rickets unresponsive to phosphate supplementation. The c.182A > G;p.(Gln61Arg) somatic NRAS variant found in DNA from nevus biopsy allowed diagnosing CSHS. We administered Trametinib for 15 months investigating the transcriptional effects at different time points by whole blood RNA-seq. Treatment resulted in prompt normalization of phosphatemia and phosphaturia, catch-up growth, chylothorax regression, improvement of bone mineral density, reduction of epidermal nevus and hamartomas. Global RNA sequencing on peripheral blood mononucleate cells showed transcriptional changes under MEK inhibition consisting in a strong sustained downregulation of signatures related to RAS/MAPK, PI3 kinase, WNT and YAP/TAZ pathways, reverting previously defined transcriptomic signatures. CSHS was effectively treated with a MEK inhibitor with almost complete recovery of rickets and partial regression of the phenotype. We identified "core" genes modulated by MEK inhibition potentially serving as surrogate markers of Trametinib action.