Molecular diagnosis of a benign proliferative nodule developing in a congenital melanocytic nevus in a 3-month-old infant

Conventional and Atypical Deep Penetrating Nevus, Deep Penetrating Nevus-like Melanoma, and Related Variants

Simple Summary

Atypical deep penetrating nevus (DPN) is a unique skin tumor with an uncertain biologic/metastatic potential that may be difficult to distinguish from DPN (an indolent lesion) and DPN-like melanoma (an aggressive lesion) based on the results of histomorphologic analysis and commonly employed molecular studies such as fluorescence in situ hybridization and comparative genomic hybridization alone. Herein, we review the clinical, histomorphological, immunohistochemical, molecular, and cytogenetic characteristics of the DPN spectrum of lesions to try to better understand the prognosis of these lesions and possible treatment approaches.

Abstract

Deep penetrating nevus (DPN) is an uncommon acquired melanocytic lesion with a distinct histopathological appearance that typically behaves in an indolent manner. The lesion is characterized by a symmetrical proliferation of epithelioid to spindled melanocytes associated with abundant melanophages and wedge-shaped extension to the deep reticular dermis and subcutis. Pronounced cytologic atypia and mitotic figures are usually absent, which helps distinguish DPN from melanoma with a deep penetrating growth pattern. Recently, the concept of atypical DPN has been proposed for lesions that demonstrate borderline histomorphologic features and may be associated with lymph node deposits but lack the copy number aberrations typical of melanoma by either fluorescence in situ hybridization or comparative genomic hybridization. While most of these lesions have a favorable clinical course, rare lesions may progress to melanoma. In this review, we summarize the current literature on atypical DPNs with uncertain behavior/metastatic potential and outline the characteristics that distinguish these lesions from conventional DPN and melanoma with DPN-like features.

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.

Proliferative nodule resembling angiomatoid Spitz tumor with degenerative atypia arising within a giant congenital nevus

Proliferative nodules arising within congenital melanocytic nevi often present a diagnostic challenge given a close resemblance to melanoma. Several morphologic variants have been characterized. In difficult cases, ancillary molecular tests can be used to better exclude the possibility of malignant degeneration. Herein, we report a case of an unusual proliferative nodule with overlapping features of angiomatoid Spitz tumor and ancient melanocytic nevus, which demonstrated normal findings on both chromosomal microarray and a gene expression profiling assay.

Deep Penetrating Nevus and Borderline-Deep Penetrating Nevus: A Literature Review

Deep penetrating nevi (DPN) are rare melanocytic nevi, which can exhibit atypical histological features hampering the differentiation from malignant melanoma. DPN are considered benign melanocytic lesions, but rare spread to lymph nodes and unfavorable clinical outcomes associated with borderline/atypical DPN (B-DPN) has been reported. Since no guidelines are available for DPN and B-DPN, we aimed to review the literature on DPN and B-DPN to assess the management and prognosis. We screened 3,513 references from EMBASE, Scopus and Medline databases, and included 15 studies with a total of 355 DPN patients and 48 B-DPN patients. Therapeutic interventions ranged from simple excision to wide excisions and sentinel lymph node biopsy (SLNB), with block lymph node dissection in some positive SLNB cases. Follow-up periods ranged from 3 months to 23 years during which a total of five recurrences, two in DPN and three in B-DPN group, and three metastases, in B-DPN group, were reported. While some of the included studies comprised clinical and histopathological correlation, few included genetic assessment. The present review highlights the need for prospective cohort studies applying composite measures to identify effective regimens of diagnostic workup and treatment in DPN and B-DPN.

New and evolving concepts of melanocytic nevi and melanocytomas

In daily clinical practice melanocytic nevi are commonly encountered. Traditionally, both benign and malignant melanocytic tumors have been sub-classified by their histopathologic characteristics with differing criteria for malignancy applied to each group. Recently, many of the mutations that initiate nevus formation have been identified and specific sets of mutations are found in different subtypes of nevi. Whereas a single mutation appears sufficient to initiate a nevus, but is not enough to result in melanoma, specific combinations of mutations have been identified in some melanocytic tumors that are regarded to be of low biologic potential. The term "melanocytoma" has recently been proposed by the World Health Organization to describe those tumors that demonstrate genetic progression beyond the single mutations that are found in nevi but are not frankly malignant. Melanocytomas occupy intermediate genetic stages between nevus and melanoma and likely have an increased risk of malignant transformation as compared to nevi. This review provides an update on the broad spectrum of melanocytic nevi and melanocytomas and outlines their key histopathologic and genetic features.

Invasive melanoma in a 5-year-old Canadian patient: A case report

Atypical Spitzoid lesions pose a distinct challenge in classification as they may comprise a mixture of both classic benign nevus and cutaneous melanoma characteristics. Immunostaining and molecular analysis, such as comparative genomic hybridization, can assist in narrowing the differential diagnosis. We present a case of a 5-year-old male with an atypical Spitzoid lesion on his back. Initial histopathology revealed a relatively symmetric lesion with mitotic figures and poor maturation of melanocytes with descent into the dermis. Immunohistochemistry demonstrated a loss of p16, and array comparative genomic hybridization revealed a loss of chromosome 9, supporting a diagnosis of invasive melanoma arising in conjunction with a remnant of a conventional melanocytic nevus. This case is the first in Canada to demonstrate the use of array comparative genomic hybridization for diagnosing melanoma in a young paediatric patient.

Mass Spectrometry Imaging Can Distinguish on a Proteomic Level Between Proliferative Nodules Within a Benign Congenital Nevus and Malignant Melanoma

Histopathological interpretation of proliferative nodules occurring in association with congenital melanocytic nevi can be very challenging due to their similarities with congenital malignant melanoma and malignant melanoma arising in association with congenital nevi. We hereby report a diagnostically challenging case of congenital melanocytic nevus with proliferative nodules and ulcerations, which was originally misdiagnosed as congenital malignant melanoma. Subsequent histopathological examination in consultation by one of the authors (R.L.) and mass spectrometry imaging analysis rendered a diagnosis of congenital melanocytic nevus with proliferative nodules. In this case, mass spectrometry imaging, a novel method capable of distinguishing benign from malignant melanocytic lesions on a proteomic level, was instrumental in making the diagnosis of a benign nevus. We emphasize the importance of this method as an ancillary tool in the diagnosis of difficult melanocytic lesions.

Reduced H3K27me3 Expression Is Common in Nodular Melanomas of Childhood Associated With Congenital Melanocytic Nevi But Not in Proliferative Nodules

The formation of a nodule within a congenital melanocytic nevus (CMN) raises concerns about possible melanoma. Most new nodular growths that develop during childhood, however, are benign proliferative nodules (PN); melanoma is very rare. The distinction of melanoma from PN can at times be difficult clinically and histopathologically, requiring ancillary molecular tests for diagnosis. Although the application of molecular methods has revealed new insights into the mutational and genomic landscape of childhood melanomas, little is known about epigenetic events that may drive the growth of a melanoma or PN in a CMN. In this study we compared the expression of H3K27me3, a key regulator in chromatin remodelling-controlled transcription, in PNs and pediatric nodular melanomas arising within medium-sized to large CMN by immunohistochemistry. Significant loss of H3K27me3 expression was seen in 4 of 5 melanomas, but not in any of the 20 PNs. This observation suggests that epigenetic events likely play a role in the pathogenesis of melanoma developing in the dermis or subcutis of CMN. Furthermore, assessing for H3K27me3 expression by immunohistochemistry may be diagnostically useful for problematic cases.

5-Hydroxymethylcytosine Expression in Proliferative Nodules Arising within Congenital Nevi Allows Differentiation from Malignant Melanoma

Differentiation of proliferative nodules in giant congenital nevi from melanoma arising within such nevi is an important diagnostic challenge. DNA methylation is a well-established epigenetic modification already observed in the earliest stages of carcinogenesis, which increases during melanoma progression. The ten-eleven translocation enzymes catalyze the oxidation of 5-methylcytosine to 5-hydroxymethylcytosine (5-hmC), which has recently been reported as an epigenetic hallmark associated with tumor aggressiveness and poor prognosis in a wide variety of cancers. In this study, we analyzed 12 proliferative nodules and 13 melanomas both arising in giant congenital nevi and matched results with a control group including 67 benign and malignant melanocytic lesions. Proliferative nodules displayed high 5-hmC expression levels (90.65%) compared with melanomas with almost complete loss of this marker (7.87%). We showed that low 5-hmC levels in melanomas correlate with downregulation of isocitrate dehydrogenase and ten-eleven translocation families of enzymes implicated in the cytosine methylation cycle. Simultaneously, these enzymes were overexpressed in proliferative nodules leading to strong 5-hmC expression. We emphasize the significance of 5-hmC loss for discrimination of melanomas from benign proliferative nodules arising within giant congenital nevi, and for establishing the correct diagnosis in ambiguous cases when histological and immunohistochemical characteristics are not sufficiently specific.

Metastatic melanoma in association with a giant congenital melanocytic nevus in an adult: controversial CGH findings

Giant congenital melanocytic nevi (GCMNs) represent a distress to patients for 2 reasons: one is disfigurement, and the other is the increased risk of developing secondary melanocytic tumors, such as benign proliferative nodules (BPNs) and malignant melanoma (MM). BPN present as a rapid growth nodule arising within a congenital melanocytic nevus (CMN) that often ulcerates, occurs in children younger than 2 years of age. BPNs arising within a CMN are exceedingly rare after childhood, and very few cases have been described in adults. Despite the worrisome clinical and histologic findings of BPN, most laboratory investigations seem to support their benignity. The distinction between MM and BPN is extremely important, but the histopathology of BPN of GCMN can be a challenge to differentiate from MM. In the recent years, molecular tests that investigate DNA copy number alterations such as fluorescence in situ hybridization and comparative genomic hybridization have shown promise to help guide the diagnosis of ambiguous melanocytic proliferations arising within CMNs. We report the case of a 22-year-old woman with a nodule arising in a GCMN and with an axillary mass suggesting a nodal metastasis of melanoma, and discuss the unusual clinical, histopathologic, and molecular findings that make this case particularly interesting.

Update on melanocytic nevi in children

A new or changing melanocytic nevus in a child or adolescent often leads to concern in parents and physicians. To avoid undue alarm and unnecessary procedures, dermatologists should be aware of the natural history and clinical spectrum of nevi in pediatric patients, as well as findings that are potentially worrisome in this age group. This review provides an update on melanocytic nevi in children, focusing on their dynamic evolution over time, molecular insights into nevogenesis, and phenotypic markers for increased risk of melanoma in adolescence and adulthood. Special considerations for Spitz nevi and nevi located in particular sites (eg, scalp, acral, genital) are highlighted. Current understanding of the risks associated with congenital melanocytic nevi of different sizes and strategies for the management of children with numerous acquired nevi, Spitz nevi, and congenital nevi are also discussed.

The deep penetrating nevus

The deep penetrating nevus (DPN), also known as the plexiform spindle cell nevus, is a pigmented lesion that commonly arises on the head and neck in the first few decades of life. Histopathologically, the DPN is wedge-shaped and contains melanocytes that exhibit deep infiltration into the dermis. Given these features, DPN may clinically and histopathologically mimic malignant melanoma, sparking confusion about the appropriate evaluation and management of these lesions. The goal of this review is to summarize the clinical and histopathological features of DPN and to discuss diagnostic and treatment strategies for dermatologists.

Congenital melanocytic nevi: where are we now? Part I. Clinical presentation, epidemiology, pathogenesis, histology, malignant transformation, and neurocutaneous melanosis

Congenital melanocytic nevi (CMN) are present at birth or arise during the first few weeks of life. They are quite common, may have a heritable component, and can present with marked differences in size, shape, color, and location. Histologic and dermatoscopic findings may help suggest the diagnosis, but they are not entirely specific. CMN are categorized based on size, and larger lesions can have a significant psychosocial impact and other complications. They are associated with a variety of dermatologic lesions, ranging from benign to malignant. The risk of malignant transformation varies, with larger CMN carrying a significantly higher risk of malignant melanoma (MM), although with an absolute risk that is lower than is commonly believed. They may also be associated with neuromelanosis, which may be of greater concern than cutaneous MM. The information presented herein aims to help dermatologists determine when it is prudent to obtain a biopsy specimen or excise these lesions, to obtain radiographic imaging, and to involve other specialists (eg, psychiatrists and neurologists) in the patient's care.

Nodular lesions arising in a large congenital melanocytic naevus in a newborn with eruptive disseminated Spitz naevi

Congenital malignant melanoma within a pre-existing large congenital melanocytic naevus (CMN) is exceedingly rare. Its incidence is difficult to determine due to the small number of reported cases and because of problems associated with diagnosis. Some benign nodular proliferations (called proliferative nodules) arising in CMN, while rare, are significantly more common and can mimic malignant melanoma clinically or histologically. There are no reported cases of congenital melanoma or benign proliferative nodules in CMN in patients who also had eruptive disseminated Spitz naevi. We describe a girl who was noted to have a dark-brown plaque with several large erythematous nodules affecting the scalp at delivery, in addition to multiple erythematous dome-shaped papules that developed in a disseminated manner over several months, beginning at 10 days of age. It was difficult, not only clinically but also histologically, to determine the benign or malignant nature of all of these lesions. As primary cutaneous melanoma, atypical proliferative nodules in CMN, bland CMN or CMN with foci of increased cellularity and Spitz naevi show clear differences in the genetic aberration patterns, comparative genomic hybridization (CGH) could be a diagnostic help in ambiguous cases such as this. CGH performed on this patient showed multiple DNA copy number changes in the most atypical nodule, but such alterations could not be found in the remainder of the lesions. CGH showed differences between the nodular lesions that occurred in the CMN and helped us in supporting the diagnosis of this unique case of benign proliferative nodules and a possible congenital melanoma arising in a large CMN, associated with multiple widespread eruptive Spitz naevi.

Molecular dermatopathology in malignant melanoma

At present, immunohistochemistry is taken for granted in the establishment of malignant melanoma (MM) diagnosis. In recent years, molecular diagnosis in dermatopathology has benefited from a vast array of advances in the fields of genomics and proteomics. Sensitive techniques are available for detecting specific DNA and RNA sequences by molecular hybridization. This paper intends to update methods of molecular cytogenetics available as diagnostic adjuncts in the field of MM. Cytogenetics has highlighted the pathogenesis of atypical melanocytic neoplasms with emphasis on the activation of the mitogen-activated protein kinase (MAPK) signalling pathway during the initiation step of the neoplasms. 20 to 40% of MM families have mutations in the tumour suppressor gene p16 or CDKN2A. In addition, somatic mutations in p16, p53, BRAF, and cKIT are present in MM. Genome-wide scan analyses on MM indicate positive associations for genes involved in melanocytic naevi, but MM is likely caused by a variety of common low-penetrance genes. Molecular dermatopathology is expanding, and its use in the assessment of melanocytic neoplasms appears to be promising in the fields of research and diagnosis. Molecular dermatopathology will probably make its way to an increased number of diagnostic laboratories. The expected benefit should improve the patient management. This evolution points to a need for evolution in the training requirements and role of dermatopathologists.

Congenital melanocytic nevi

This article reviews congenital melanocytic nevi (CMN), which are present at birth or appear shortly thereafter, and their main histologic features. Several histologic variants and histopathologic criteria that differentiate CMN from other nevi, such as atypical or dysplastic nevi, and from nevoid malignant melanoma, are discussed. Histologic pitfalls in the correct identification of lentiginous melanocytic hyperplasia, pagetoid scatter, and proliferative nodules in the context of CMN are discussed. The risk for development of malignant melanoma in association with a congenital melanocytic nevus and variable causes for changing mole are discussed.

The risk of melanoma and neurocutaneous melanosis associated with congenital melanocytic nevi

Congenital melanocytic nevi are commonly encountered in clinical practice. Although the development of malignant melanoma arising in small and intermediate congenital melanocytic nevi is rare, there is a significant risk of malignant degeneration associated with large congenital melanocytic nevi, in particular those that arise on the torso in the so-called "bathing trunk" distribution, where the risk is estimated to be about 2.5% to 5%. The risk of malignant melanoma arising within a large congenital melanocytic nevus is highest in the first 5 to 10 years of life and carries a significant mortality. Large congenital melanocytic nevi, in particular those overlying the posterior axis and occurring in the context of multiple satellite melanocytic nevi, are also associated with the development of neurocutaneous melanosis, which may result in neurologic and neurodevelopmental sequelae and is associated with a significant risk of primary central nervous system melanoma and death.

Congenital melanocytic nevi-when to worry and how to treat: Facts and controversies

Congenital melanocytic nevi (CMN) are evident in 1% to 6% of neonates. In some studies, nevi with clinical, dermatoscopic, and histologic features identical to CMN have had a prevalence of more than 15% in older children and adults, possibly reflecting the "tardive" appearance of nevi programmed from birth. There is ongoing debate about the magnitude of the risk of melanoma and other complications associated with CMN of various sizes and the best approach to management of these lesions. We review the natural history of CMN, including proliferative nodules and erosions during infancy, neurotization, and spontaneous regression, and features of variants such as speckled lentiginous and congenital blue nevi. The risk of melanoma arising within small-sized (<1.5 cm) and medium-sized CMN is low (likely <1% over a lifetime) and virtually nonexistent before puberty. Recent data suggest that melanoma (cutaneous or extracutaneous) develops in approximately 5% of patients with a large (>20 cm) CMN, with about half of this risk in the first few years of life. Melanoma and neurocutaneous melanocytosis (NCM) are most likely in patients with CMN that have a final size of >40 cm in diameter, numerous satellite nevi, and a truncal location. One-third of individuals with NCM have multiple medium-sized (but no large) CMN. In patients at risk for NCM, a screening gadolinium-enhanced magnetic resonance imaging, preferably before age 6 months, and longitudinal neurologic assessment are recommended. Management of CMN depends on such factors as the ease of monitoring (more difficult for large, dark, thick nevi) and cosmetic and psychologic benefits of excision or other procedures. CMN require lifelong follow-up. Periodic total body skin examinations are necessary for all patients with large CMN, even when complete resection (often impossible) has been attempted.

Comparative genomic hybridization for the diagnosis of melanoma

Despite advancements in protocols, a subset of melanocytic lesions continues to pose diagnostic challenges. This is particularly true in the pediatric population where certain congenital nevi mimic melanoma. Recently, comparative genomic hybridization (CGH) has been utilized to support diagnoses of melanocytic lesions based on DNA copy number changes. Because distinct differences in copy number changes have been shown to occur in malignant melanoma and benign nevi, CGH can be a useful adjunct when diagnosis based on histology alone is indeterminate. The authors discuss the benefits of using CGH to aid in the diagnosis of melanocytic lesions that are difficult to characterize as malignant or benign based on clinical and histologic features alone. This paper presents a brief clinical report and review of the literature. A 13-year-old Caucasian male presented to an academic tertiary care medical center after a shave biopsy unexpectedly revealed malignant melanoma with positive deep margins. Following complete excisional biopsy, the diagnosis of malignant melanoma with depth of 0.92 mm was confirmed, both by the home institution's pathologist and by consultant dermatopathologists at two separate academic tertiary medical centers. Sentinel lymph node biopsy revealed a small focus of metastatic melanoma, this lead to a left-sided modified radical neck dissection. All nodes removed were negative for disease, and surgical and postsurgical care was uncomplicated. Before proceeding with interferon therapy, CGH was performed on the tissue from the primary lesion. Other than a slight amplification of chromosome 16p, no other aberrations were detected favoring a benign lesion. Ultimately, the diagnosis was amended to compound melanocytic nevus of the nose with benign nevus cell rest in the sentinel node. While histopathologic evaluation is the current gold standard for the diagnosis of melanoma, there are many cases where it is inaccurate. The use of CGH in the evaluation of histologically equivocal lesions may allow certain patients to avoid invasive procedures and associated morbidities. The authors propose that, in these select diagnostically challenging cases, tissue analyses by CGH may be beneficial before proceeding to more invasive procedures such as sentinel node biopsy and complete lymphadenectomy.

Proliferative nodules in a giant congenital melanocytic nevus-case report and review of the literature

Malignant transformation of giant congenital nevi (GCN) is very rare, but may already occur in childhood. Benign proliferative nodules in GCN may clinically and histologically mimic a malignant melanoma. We report a newborn infant with large proliferative nodules and multiple satellite nevi in a GCN of the bathing suit type. The diagnosis in our patient was based on the smooth transition of the pre-existing lesion and the nodule, the absence of strong atypical nuclei, the atypical mitotic figures, the ascension of melanocytes in the epidermis and the absence of necrosis. A review of the literature showed that the clinical and the histological features of benign (proliferative) nodules are variable. The awareness and the identification of this entity by clinicians and pathologist are imperative to prevent diagnostic errors.

Congenital Melanocytic Nevi

This article reviews congenital melanocytic nevi (CMN), which are present at birth or appear shortly thereafter, and their main histologic features. Several histologic variants and histopathologic criteria that differentiate CMN from other nevi, such as atypical or dysplastic nevi, and from nevoid malignant melanoma, are discussed. Histologic pitfalls in the correct identification of lentiginous melanocytic hyperplasia, pagetoid scatter, and proliferative nodules in the context of CMN are discussed. The risk for development of malignant melanoma in association with a congenital melanocytic nevus and variable causes for changing mole are discussed.

Pediatric Melanoma: A Review

Background

Malignant mela-noma is a rare neoplasm in the pediatric population, but its incidence has risen in recent years.

Methods

The literature was reviewed to define the current clinical and pathologic features of pediatric melanoma, highlighting the similarities and differences between adult and pediatric melanoma.

Results

Distinctive features of this disease, including frequency and type of genetic abnormalities, predisposing conditions, clinical presentation, stage at diagnosis, prognostic features, and frequency of sentinel lymph node positivity are emphasized. Treatment strategies, extrapolated from adult mela-noma trials, are also discussed.

Conclusions

Despite the differences between pediatric and adult melanoma, survival rates are similar and are improving in both populations. Further studies will help delineate the pathogenesis of both adult and pediatric melanoma, with the goal of contributing to early detection and improved survival.