Congenital melanocytic nevi: update in genetics and management

Prevalence, incidence density and standardized morbidity rate of melanoma among patients with congenital melanocytic naevi: a systematic review

BACKGROUND

Congenital melanocytic naevi (CMN) are the result of aberrations in the mitogen-activated protein kinase signal transduction pathway. The risk of melanoma is the most important concern among patients with CMN because of its poor prognosis. However, as a result of the great variability between studies, the reported risk of melanoma varies considerably, making it difficult to provide reliable information.

OBJECTIVES

To evaluate the prevalence, incidence density and standardized morbidity ratio (SMR) of melanoma among patients with CMN.

METHODS

We conducted a systematic literature search of studies providing data on the risk of melanoma in patients with CMN following our registered and published protocol (PROSPERO: CRD42022383009).

RESULTS

Overall, 27 studies with a total of 11 480 patients with CMN and 82 patients developing melanoma were included for analysis. The prevalence of melanoma was 1.84% [95% confidence interval (CI) 1.13-2.99] in patients with CMN and 2.73% (95% CI 1.67-4.43) in the subgroup of patients with large CMN (LCMN). The incidence of melanoma was 237.56 (95% CI 97.79-575.96) per 100 000 person-years in patients with CMN and 585.73 (95% CI 315.39-1085.29) per 100 000 person-years in the LCMN subgroup. The SMR of melanoma was 122.27 (95% CI 11.84-1262.88) among all patients with CMN and 285.97 (95% CI 50.65-1614.59) in the subgroup of patients with LCMN.

CONCLUSIONS

Our research suggests that the risk of melanoma in the CMN population seems to have been overestimated in previous studies, but it is still significantly higher than that in the general population. In addition to the risk of melanoma, aesthetic improvement and mental health should also be taken into account when making management decisions.

Updates in the Management of Congenital Melanocytic Nevi

Congenital melanocytic nevi (CMN) carry an increased risk of melanoma and may be disfiguring, and consensus regarding treatment recommendations is lacking. While clinical monitoring is the standard of care, many caregivers are interested in its removal to prevent psychosocial burden or to decrease risk. Although melanoma can occur regardless of CMN removal, there are a variety of treatments that may offer improved cosmesis or local symptom control, including surgical excision, laser therapy, and other superficially destructive techniques. Regardless of the selected management, these patients are monitored for ongoing melanoma risk. An extensive discussion with families regarding the risks and benefits of observation versus active intervention is essential. To facilitate these discussions, we herein summarize current CMN management strategies and considerations.

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.

BRAF Immunohistochemical Studies of Pediatric Conjunctival Lesions

PURPOSE

The purpose of this study was to analyze the prevalence of an activating mutation in the B-Raf proto-oncogene (BRAF) V600E immunoreactivity in pediatric conjunctival lesions.

METHODS

This retrospective case-control study included 32 pediatric patients who underwent surgical excision of conjunctival lesions between Jan 2019 and May 2022. The collected data included demographic data, clinical features, and histopathologic characteristics of the lesion, including BRAF V600E positivity. The Student t test and the Fisher exact test were used to determine the significance of the associations between clinical variables and BRAF positivity.

RESULTS

BRAF immunoreactivity was positive in 11/32 lesions (34%). Age at diagnosis did not correlate with BRAF positivity, with a mean age at diagnosis of 131.7 months for patients with BRAF+ lesions and 134.7 months for those with BRAF- lesions ( P > 0.1). No clinical or pathological features were found to be significantly correlated with BRAF positivity, although there was a trend toward BRAF positivity in the presence of cysts ( P = 0.072).

CONCLUSIONS

BRAF reactivity was present in approximately one-third of pediatric conjunctival nevi but does not correlate significantly with unique clinical or histopathological features.

Risk of melanoma in congenital melanocytic nevi of all sizes: A systematic review

Congenital melanocytic nevi (CMN) are commonly encountered benign skin lesions in newborns. Larger CMN is associated with a higher lifetime risk of developing melanoma. However, the level of risk is unclear when CMN are small or medium-sized. Our objective was to assess melanoma risk in patients with CMN of all size categories. A literature review with meta-analysis was performed. Prevalence and incidence densities of melanoma at onset were calculated in the entire study population and according to CMN size, type of treatment and location of the CMN. A total of 91 melanomas were reported in 7915 patients (1.15%, 95% CI, 0.93-1.41). The overall incidence density was 0.057% person-years (95% CI_, 0.044-0.071). The risk ratio of melanoma incidence densities was 21.9 (95% CI, 8.55-56.3) in large to giant CMN compared with small to medium CMN at 15 years of age. The incidence density was higher in CMN located on the trunk and as well as in those which were untreated or partially treated versus complete excision. Our review suggests patients with CMN of medium, large and giant size are at risk of melanoma, whereas the risk remains unknown for small CMN.

Topical therapy for regression and melanoma prevention of congenital giant nevi

Giant congenital melanocytic nevi are NRAS-driven proliferations that may cover up to 80% of the body surface. Their most dangerous consequence is progression to melanoma. This risk often triggers preemptive extensive surgical excisions in childhood, producing severe lifelong challenges. We have presented preclinical models, including multiple genetically engineered mice and xenografted human lesions, which enabled testing locally applied pharmacologic agents to avoid surgery. The murine models permitted the identification of proliferative versus senescent nevus phases and treatments targeting both. These nevi recapitulated the histologic and molecular features of human giant congenital nevi, including the risk of melanoma transformation. Cutaneously delivered MEK, PI3K, and c-KIT inhibitors or proinflammatory squaric acid dibutylester (SADBE) achieved major regressions. SADBE triggered innate immunity that ablated detectable nevocytes, fully prevented melanoma, and regressed human giant nevus xenografts. These findings reveal nevus mechanistic vulnerabilities and suggest opportunities for topical interventions that may alter the therapeutic options for children with congenital giant nevi.

Giant Congenital Melanocytic Nevus in a Pediatric Patient: Case Report

The giant congenital melanocytic nevus is a rare entity with an extremely low incidence that appears at the time of birth and generally involves the dermis but may also affect other skin layers. According to its clinical evolution, the probability of malignancy may vary, so proper follow-up is essential for potential management. There is no consensus in the literature about the greater benefit of surgical versus nonsurgical management. In this case report, we present the surgical management of a school-aged patient using dermal substitutes and skin grafts, subjectively obtaining an improvement in his quality of life.

The retrospective molecular analysis of large or giant congenital melanocytic nevi in a group of Polish children

Background

Large and giant congenital melanocytic nevi (CMN), benign naevomelanocytic proliferations derived from neural crests, with a projected adult size (PAS) ≥ 20 cm, are connected to a high risk of melanoma and neurocutaneous melanosis. Among several factors, genetic alterations seem to be involved in tumorigenesis. The aim of the present study was to analyse the mutation status of NRAS and BRAF genes in resection specimens from large or giant CMN in a group of Polish patients.

Material and methods

The formalin-fixed, paraffin-embedded resection specimens from 18 patients, fixed in the years of 2006 to 2017, were included in the study. The regions containing the highest load of melanocytes were macrodissected prior to DNA isolation. The NRAS and BRAF mutation status was evaluated using qPCR.

Results

We detected activating mutations in NRAS gene (codons: 12 and 61) in 7 out of the 18 (38.9%) patients. No BRAF mutations were found.

Conclusion

Our study, the first molecular analysis of large/giant CMN in Polish patients, supports the hypothesis that NRAS mutation in codon 61 are frequent, recurrent mutations in large/giant CMN. Moreover, we show, for the first time, that NRAS mutations in codon 12 (p.Gly12Asp) can be also detected in giant CMN. The exact role of these genetic alterations in CMN formation remains to be elucidated.

Congenital melanocytic naevi: An up-to-date overview

Congenital melanocytic naevi are hamartomas of the neuroectoderm caused by genetic mosaicism. Congenital melanocytic naevi are seen in 1-6% of all live births and commonly classified based on the projected size in adults. Congenital melanocytic naevi appear in different colours, shapes, and sizes, and occasionally present with complications. In this review, we sought to evaluate congenital melanocytic naevi, their clinical, dermatoscopic, and reflectance confocal microscopic features, behavioural pattern over time, new trends in classification, underlying genetic factors and their influence on clinical manifestations and management, associated risks, complications, magnetic resonance imaging findings and their management in the light of recent literature.

Divided Eyelid Nevus: Surgical Repair Discussion and Case Reports From Northwestern China

Currently, due to the lack of long-term postoperative follow-up outcomes of the congenital divided eyelid nevus, we described our surgical approaches and presented the functional and cosmetic results of 13 patients with an average of 5-year follow-up. Based on the surgical treatments and the follow-ups, the selection of total or subtotal excision depends on the lesion location and the use of blepharoplasty approaches is determined by defect size. The CO₂ laser may be a useful second-stage procedure to ablate remnant lesions, but long-term monitoring is required.

A Clinicoepidemiological Study of Melanoma in Young Patients (20 Years of Age or Less) in Alberta, Canada, From 1992 to 2011

The epidemiological trends of malignant melanoma have been well described in the literature. However, there remains a paucity of population-based studies assessing melanoma epidemiology in our younger patients (20 years of age or less). Other studies indicate that melanoma incidence has risen in pediatric populations over the last several decades and that these tumors may display different clinical characteristics from those arising in adult populations. We conducted a retrospective, population-based analysis of all incident cases of melanoma occurring in young patients aged ≤20 years in Alberta from 1992 to 2011. Information, including patient age, sex, anatomical location, date of diagnosis, histological subtype (if available), level of invasion, and date of death (if applicable), was obtained from the Alberta Cancer Registry. All cases occurring during a 10-year period from 1993 to 2011 have been reviewed. A total of 71 cases were diagnosed during this time (63% female and 37% male). Age range was 0-20 years (mean of 17.5 years). Truncal melanomas made up 36% of cases, while 28% occurred on the lower limbs, 17% on the upper limbs, and 18% in the head and neck region. Average Breslow thickness was 1.97 mm; 67% of tumors were less than 1 mm thick. Unfortunately, 8 of 71 patients died from their disease. Overall, the incidence of melanoma in patients aged ≤20 years appeared to decrease in Alberta in the past 20 years; however, there has been an increase in the thickness of melanoma at diagnosis, which needs to be addressed.

EGFR and BRAF mutations in inverted sinonasal papilloma - a more complex landscape?

Inverted (Schneiderian) sinonasal papilloma (ISP) is a neoplasm derived from mucosa of the sinonasal tract characterized by local aggressive growth, a tendency to recur and an association with sinonasal carcinoma. The etiology of ISP remains unclear. Recently, identical mutations in exons 19 and 20 of the oncogene EGFR were reported in ISP and ISP-associated sinonasal carcinoma. Nevertheless, it remains unclear whether recurring ISPs show identical EGFR mutations at different time points or whether these mutations are identical throughout the respective ISP sample. We used Sanger sequencing to test 60 formalin-fixed paraffin embedded ISP samples from 40 patients regarding mutations in exons 19 and 20 of EGFR—together with exon 15 of BRAF. Overall, 32 samples of 22 patients showed a mutation in EGFR exon 20, whereas 28 samples of 18 patients showed none. No mutation in EGFR exon 19 was found in any sample. Four samples of four patients showed a BRAF exon 15 mutation. Interestingly, samples of four patients exhibited genetic heterogeneity, enabling us to report this in ISP for the first time.

Neurocutaneous melanocytosis (melanosis)

Neurocutaneous melanosis (NCM; MIM # 249400; ORPHA: 2481], first reported by the Bohemian pathologist Rokitansky in 1861, and now more precisely defined as neurocutaneous melanocytosis, is a rare, congenital syndrome characterised by the association of (1) congenital melanocytic nevi (CMN) of the skin with overlying hypertrichosis, presenting as (a) large (LCMN) or giant and/or multiple (MCMN) melanocytic lesions (or both; sometimes associated with smaller "satellite" nevi) or (b) as proliferative melanocytic nodules; and (2) melanocytosis (with infiltration) of the brain parenchyma and/or leptomeninges. CMN of the skin and leptomeningeal/nervous system infiltration are usually benign, more rarely may progress to melanoma or non-malignant melanosis of the brain. Approximately 12% of individuals with LCMN will develop NCM: wide extension and/or dorsal axial distribution of LCMN increases the risk of NCM. The CMN are recognised at birth and are distributed over the skin according to 6 or more patterns (6B patterns) in line with the archetypical patterns of distribution of mosaic skin disorders. Neurological manifestations can appear acutely in infancy, or more frequently later in childhood or adult life, and include signs/symptoms of intracranial hypertension, seizures/epilepsy, cranial nerve palsies, motor/sensory deficits, cognitive/behavioural abnormalities, sleep cycle anomalies, and eventually neurological deterioration. NMC patients may be symptomatic or asymptomatic, with or without evidence of the typical nervous system changes at MRI. Associated brain and spinal cord malformations include the Dandy-Walker malformation (DWM) complex, hemimegalencephaly, cortical dysplasia, arachnoid cysts, Chiari I and II malformations, syringomyelia, meningoceles, occult spinal dysraphism, and CNS lipoma/lipomatosis. There is no systemic involvement, or only rarely. Pathogenically, single postzygotic mutations in the NRAS (neuroblastoma RAS viral oncogene homologue; MIM # 164790; at 1p13.2) proto-oncogene explain the occurrence of single/multiple CMNs and melanocytic and non-melanocytic nervous system lesions in NCM: these disrupt the RAS/ERK/mTOR/PI3K/akt pathways. Diagnostic/surveillance work-ups require physical examination, ophthalmoscopy, brain/spinal cord magnetic resonance imaging (MRI) and angiography (MRA), positron emission tomography (PET), and video-EEG and IQ testing. Treatment strategies include laser therapy, chemical peeling, dermabrasion, and surgical removal/grafting for CMNs and shunt surgery and surgical removal/chemo/radiotherapy for CNS lesions. Biologically targeted therapies tailored (a) BRAF/MEK in NCM mice (MEK162) and GCMN (trametinib); (b) PI3K/mTOR (omipalisib/GSK2126458) in NMC cells; (c) RAS/MEK (vemurafenib and trametinib) in LCMNs cells; or created experimental NMC cells (YP-MEL).

A six-attribute classification of genetic mosaicism

Mosaicism denotes an individual who has at least two populations of cells with distinct genotypes that are derived from a single fertilized egg. Genetic variation among the cell lines can involve whole chromosomes, structural or copy number variants, small or single nucleotide variants, or epigenetic variants. The mutational events that underlie mosaic variants occur during mitotic cell divisions after fertilization and zygote formation. The initiating mutational event can occur in any types of cell at any time in development, leading to enormous variation in the distribution and phenotypic effect of mosaicism. A number of classification proposals have been put forward to classify genetic mosaicism into categories based on the location, pattern, and mechanisms of the disease. We here propose a new classification of genetic mosaicism that considers the affected tissue, the pattern and distribution of the mosaicism, the pathogenicity of the variant, the direction of the change (benign to pathogenic vs. pathogenic to benign), and the postzygotic mutational mechanism. The accurate and comprehensive categorization and subtyping of mosaicisms is important and has potential clinical utility to define the natural history of these disorders, tailor follow-up frequency and interventions, estimate recurrence risks, and guide therapeutic decisions.

Malignant melanoma in a child with giant congenital melanocytic nevus and satellite flekers: A rare entity

Malignant melanomas in the pediatric age are remarkably rare representing 0.9% of various pediatric malignancies. Congenital nevi occur in 1 in 100 newborns, whereas giant congenital melanocytic nevus (GCMN) measuring more than 20 cm is seen in 1 in 20 000 cases. Very few cases of malignant melanoma arising from GCMN have been described in English literature. The risk of developing malignant melanoma from GCMN is believed to be directly proportional to the size of the nevus and varies from 2.6% to 20% depending on the size of nevus. We present a case of malignant melanoma in a 12-year-old female child who had a congenital giant nevus and multiple satellite flekers all over the body.

Giant melanocytic nevi and soft tissue undergrowth in the left leg: Pathogenetic hypothesis

Congenital melanocytic nevi (CMN) are observed frequently in children. The anomalous skin shows a widely variable clinical expression not only in the anatomic location, but also in color, morphology and superficial structure. According to the width CMN are distinguished in small, medium, large or giant. Aside the cosmetic problem and its psychological implications, CMN may present with severe complications consisting of malignant transformation and/or central nervous system involvement. We report on a 3-month old infant with an extensive CMN in the left leg, which extended from the lower portion of the knee to the foot, with satellite nevi. Concomitant with the extensive nevi in the same district a remarkable reduction in size was present, and involved the adipose and muscle tissues, contributing to a counterpart diameter difference of 5 cm, without bone involvement. Melanocytic nevi and soft tissue undergrowth in the leg is a usual association; a pathogenic explanation on the anomaly involving concomitantly the skin and the underneath soft tissues is advanced.

Paediatric melanoma: clinical update, genetic basis, and advances in diagnosis

Paediatric melanoma is rare and challenging to diagnose. The three subtypes are Spitzoid melanoma, melanoma arising in a congenital melanocytic nevus, and conventional (also known as adult-type) melanoma. Spitzoid melanomas have characteristic histopathological and genomic aberrations. Despite frequent involvement of the sentinel lymph nodes, most cases have an uneventful clinical course. Among congenital nevi, the risk of melanoma varies by projected size in adulthood, with the greatest risk in large or giant nevi. The clinical course is generally aggressive and accounts for most melanoma-related deaths in childhood. In conventional melanoma, superficial spreading and nodular melanoma account for most cases, with risk factors and presentation largely similar to adult disease. In this Review, we discuss advances in histological diagnosis using adjunctive molecular assays, and summarise the genetic basis of paediatric melanoma.

Evolution of congenital melanocytic nevi toward benignity: A case series

We report on four children born with medium to large congenital melanocytic nevi (CMN) with color heterogeneity and irregular surface rugosity. As these patients aged, their nevi evolved to become more homogeneous and lighter in color, and developed a smoother, more even texture. We propose that given this evolution toward benignity, conservative monitoring and management may be appropriate even in the context of atypical-appearing features at birth. Such knowledge regarding the evolution of these CMN can more accurately guide parents and clinicians in determining whether to biopsy or remove an atypical-looking lesion early in life for medical or cosmetic reasons.

Melanoma arising in a Giant congenital melanocytic nevus: two case reports

Background

A giant congenital melanocytic nevus (GCMN) is found in 0.1% of live-born infants. If present, the lesion has a chance of about 6% to develop into malignant melanoma. Both children and adults can be affected by malignant melanoma arising in a giant congenital nevus. Up to 95% of GCMNs harbor NRAS mutations, and mutations in the BRAF, MC1R, TP53, and GNAQ genes have also been described. The individualization of therapy is required, but diagnostic and prognostic criteria remain controversial.

Case presentations

We report two cases: 1) melanoma arising in a giant congenital nevus during the first month of life complicated with neurocutaneous melanosis (NCM), and 2) melanoma arising in a giant congenital nevus during the first 6 months of life. Pathology, immunohistochemistry, and genetic analyses of tumor tissue were performed. The first case revealed only a non-pathogenic P72R polymorphism of the TP53 gene in the homozygote condition. For the second case, a Q61K mutation was detected in the NRAS gene.

Conclusion

Malignant melanoma associated with GCMN is rare and therefore poorly understood. Outcomes have been linked to the stage at diagnosis, but no additional pathological prognostic factors have been identified. The most frequent genetic event in giant CMNs is NRAS mutations, which was discovered in one of our cases. To accumulate evidence to improve disease prognosis and outcomes, children with congenital melanocytic nevus should be included in a systemic follow-up study from birth.

BRAF, NRAS, and GNAQ Mutations in Conjunctival Melanocytic Nevi

Purpose

To evaluate BRAF, NRAS, and GNAQ mutations in surgical specimens of common and blue conjunctival melanocytic nevi.

Methods

Surgical specimens from 25 conjunctival melanocytic nevi (23 common and 2 blue) of 25 patients were evaluated. All common nevi were analyzed immunohistochemically for the expression of BRAF V600E or NRAS Q61R. One lesion with negative immunoreactivity and for all blue nevi, a hybridization capture-based next-generation sequencing method was employed for mutation analysis. For common nevi, genetic features were compared with clinical and histopathologic findings. Continuous variables (age at excision and largest basal diameter) were compared with a Students's t-test and all categoric variables were compared with Fisher's Exact Test.

Results

Of common melanocytic nevi, 9 (39.1%) were immunoreactive for NRASQ61R and 13 (56.5%) were immunoreactive for BRAFV600E. One common nevus, which was immunonegative for both BRAFV600E and NRASQ61R was found to harbor an NRASQ61K mutation by sequence analysis. Patients with NRAS-mutated nevi were more likely to report occurrence of the lesion prior to 18-years old and more likely to have intrinsic cysts. The mean largest basal diameter was 6.0 and 3.5 mm for NRAS- and BRAF-immunoreactive lesions, respectively (P = 0.003). GNAQ mutations were identified in each of the two blue nevi of this study.

Conclusions

These findings document that common conjunctival melanocytic nevi have mutually exclusive mutations in BRAF and NRAS. The two conjunctival blue nevi harbored GNAQ mutations. This suggests the driver mutations of conjunctival nevi are similar to those of nevi of the skin. At the molecular level, conjunctival nevi appear more like cutaneous nevi than choroidal nevi.

Giant congenital melanocytic nevus in a Cameroonian child: a case report

BACKGROUND

Giant congenital melanocytic nevus is a very rare condition characterized by a large skin lesion and an increased risk of complications like neurocutaneous melanosis and malignant transformation. Reports of giant congenital melanocytic nevus are scarce in the sub-Saharan African literature and here we present a case of this disease in a Cameroonian adolescent.

CASE PRESENTATION

A 12-year-old Cameroonian girl from the "Baka" ethnic group, with no relevant family and medical histories presented with a progressively extensive brownish-black nodular hypertrophic skin lesion of approximately 45 cm, which she had had since she was 2-days old. The lesion covered her entire back giving an appearance of "turtle child", which was highly suggestive of a giant congenital melanocytic nevus. She was booked in for a surgical intervention organized by a health campaign within her community. Meanwhile she was provided with psychological support and her family was counseled on warning signs of complications which would warrant an urgent consultation.

CONCLUSIONS

Here we presented a case of giant congenital melanocytic nevus, apparently the first in the Cameroonian literature. In view of the potential severe complications as well as psychological trauma of this pathology, we draw clinicians' attention to this extremely rare but real pathology in our country, for a timely diagnosis and management.

Paediatric melanoma

Paediatric melanoma, although rare, is the most common skin cancer in children. Our current knowledge on paediatric melanoma incidence trends is expanding, as several studies have addressed this issue with conflicting results. Known risk factors for paediatric melanoma include family history of melanoma, a previous history of malignancy, large congenital nevi, numerous melanocytic nevi, sunburns, increased UV exposure and a sun-sensitive phenotype. In younger children, melanoma more often presents with atypical features, such as a changing, amelanotic or uniformly coloured, often bleeding lesion, not fulfilling in most cases the conventional ABCDE criteria. The major differential diagnoses are melanocytic nevi, proliferative nodules in congenital nevi and atypical Spitz tumours. Moreover, in the younger age group non-Caucasian children are over-represented, tumours tend to be thicker and lymph nodes are often involved. Despite the frequent diagnosis at an advanced stage, the overall survival is fair in paediatric melanoma. Specific guidelines for management of melanoma in children do not exist, and most often the disease is treated similarly to melanoma in adults.