Activating mutations of the GNAQ gene: a frequent event in primary melanocytic neoplasms of the central nervous system

Whole-genome copy-number analysis identifies new leads for chromosomal aberrations involved in the oncogenesis and metastastic behavior of uveal melanomas

To further elucidate the genetic underpinnings of uveal melanoma (UM) and identify new markers that correlate with disease outcome, archival formalin-fixed, paraffin-embedded enucleation specimens from 25 patients with UM and a mean follow-up of 14 years were analyzed for whole-genome copy-number alterations using OncoScan analysis. Copy-number alterations of chromosomes 1, 3, 6, and 8 were also analyzed in these tumors using multiplex ligation-dependent probe-amplification, and mutations in GNAQ, GNA11, and BAP1 were searched for by Sanger sequencing. Our study confirms the previously reported GNAQ and GNA11 mutation frequencies in UMs as well as the presence of monosomy 3 as a factor strongly indicating poor prognosis. Two cases with metastatic disease, but without monosomy of chromosome 3, showed loss of a small region in the distal part of chromosome 2p. Also, UMs leading to metastatic disease had more chromosomal aberrations than those without metastases. Three UMs lacking a GNAQ or a GNA11 mutation showed a gain of chromosome 8q; one of these cases showed extensive chromothripsis. Another case (with suspect lung metastasis) showed focal chromothripsis. Our whole-genome copy-number analysis shows that focal loss of chromosome 2p may be involved in the metastatic spread of UMs without monosomy 3; metastatic UMs carry more chromosomal aberrations than those without metastases; and chromothripsis may play a role in the oncogenesis of UMs, but does not necessarily indicate a poor prognosis. The clinical and particularly diagnostic utility of these findings needs to be corroborated in a larger set of patients with UM.

Investigation of Somatic GNAQ, GNA11, BAP1 and SF3B1 Mutations in Ophthalmic Melanocytomas

PURPOSE

The aim of this study was to use massively parallel DNA sequencing to identify GNAQ/11, BAP1 and SF3B1 mutations in ophthalmic melanocytoma.

PROCEDURES

Six ophthalmic melanocytoma specimens (1 iridociliary and 5 optic nerve) were profiled for genomic alterations in GNAQ/11, BAP1 and SF3B1 using a custom deep sequencing assay. This assay uses solution phase hybridization-based exon capture and deep-coverage massively parallel DNA sequencing to interrogate all protein-coding exons and select introns.

RESULTS

The only iridociliary melanocytoma showed a mutation in GNAQ but not in BAP1. Of the 2 optic-nerve melanocytomas that developed into melanoma, one had a GNAQ mutation and both a BAP1 mutation and monosomy 3. The remaining 3 optic-nerve melanocytomas did not reveal mutations in GNAQ/11 or BAP1. SF3B1 mutations were not detected in any specimen.

CONCLUSIONS

The presence of GNAQ mutation in some iridociliary and optic-nerve melanocytomas suggests a possible relationship between ophthalmic melanocytoma and other ophthalmic melanocytic neoplasms. BAP1 mutation may accompany the transformation of ophthalmic melanocytoma to melanoma.

SF3B1 and EIF1AX mutations occur in primary leptomeningeal melanocytic neoplasms; yet another similarity to uveal melanomas

Introduction

Like uveal melanomas, primary leptomeningeal melanocytic neoplasms (LMNs) frequently carry GNAQ and GNA11 mutations. However, it is currently unknown whether these LMNs harbor mutations in BAP1, SF3B1 and/or EIF1AX like uveal melanomas as well. In this study, we used Sanger sequencing for the detection of mutations in SF3B1 (hotspots in exon 14 and 15) and EIF1AX (exon 1 and 2 and flanking intronic regions) in a series of 24 primary LMNs. Additionally, BAP1 immunohistochemistry was used as a surrogate marker for the detection of inactivating mutations in the BAP1 gene.

Results

Mutations in either SF3B1 or EIF1AX were identified in 8 out of 24 primary LMNs (33 %). The presence of these mutations was mutually exclusive and occurred in primary LMNs of different malignancy grades (melanocytomas, intermediate-grade melanocytic tumors, melanomas). Complete absence of nuclear BAP1 staining as is typically seen in BAP1-mutated tumors was not observed.

Conclusions

Our finding that an SF3B1 or EIF1AX mutation is present in a substantial subset of primary LMNs underscores that these tumors genetically resemble uveal melanoma and are different from cutaneous melanoma at the genetic level. This information may not only aid in the differential diagnosis of primary versus metastatic melanocytic tumor in/around the central nervous system, but also in the identification of more promising therapeutic approaches targeting the molecular pathways involved in the oncogenesis of LMNs. As none of the primary LMNs in our series showed complete loss of nuclear BAP1 protein, it is unlikely that BAP1 mutations are frequent in these tumors but the role of this gene warrants further investigation.

Targeted next generation sequencing reveals unique mutation profile of primary melanocytic tumors of the central nervous system

Melanocytic tumors originating in the central nervous system (MT-CNS) are rare tumors that generally have a favorable prognosis, however malignant tumors do occur. Pathogenetically MT-CNS are not well characterized. Similar to uveal melanoma and blue nevi, they frequently harbor activating GNAQ or GNA11 mutations. Rare NRAS mutations have also been reported. Other mutations have not yet been described. We analyzed 19 MT-CNS, 7 uveal melanomas and 19 cutaneous melanomas using a targeted next generation sequencing approach analyzing 29 genes known to be frequently mutated in other melanocytic tumors (in particular uveal and cutaneous melanomas). In concordance with previous studies, cutaneous melanoma samples showed frequent NRAS or BRAF mutations, as well as mutations in other genes (e.g. NF1, RAC1, PIK3CA, ARID1A). Metastasized uveal melanomas exhibited mutations in GNAQ, GNA11 and BAP1. In contrast, MT-CNS almost exclusively demonstrated mutations in GNAQ (71 %) or GNA11 (12 %). Interestingly both GNA11 mutations identified were detected in MT-CNS diagnosed as intermediate grade melanocytomas which also recurred. One of these recurrent cases also harbored an inactivating BAP1 mutation and was found to have lost one copy of chromosome 3. Our findings show that while MT-CNS do have GNAQ or GNA11 mutations, they rarely harbor other recurrent mutations found in uveal or cutaneous melanomas. Considering chromosome 3 and BAP1 loss are robust markers of poor prognosis in uveal melanoma, it will prove interesting to determine whether these genomic alterations are also of prognostic significance in MT-CNS.

Melanoma Epidemiology and Prevention

The epidemiology of melanoma is complex, and individual risk depends on sun exposure, host factors, and genetic factors, and in their interactions as well. Sun exposure can be classified as intermittent, chronic, or cumulative (overall) exposure, and each appears to have a different effect on type of melanoma. Other environmental factors, such as chemical exposures-either through occupation, atmosphere, or food-may increase risk for melanoma, and this area warrants further study. Host factors that are well known to be important are the numbers and types of nevi and the skin phenotype. Genetic factors are classified as high-penetrant genes, moderate-risk genes, or low-risk genetic polymorphisms. Subtypes of tumors, such as BRAF-mutated tumors, have different risk factors as well as different therapies. Prevention of melanoma has been attempted using various strategies in specific subpopulations, but to date optimal interventions to reduce incidence have not emerged.

Primary intramedullary melanocytoma in the cervical spinal cord: Case report and literature review

A 63-year-old man with right hemiparesis was found (on MRI) to have an expansive intramedullary tumorous lesion at the C2-C3 level. After complete neurosurgical tumor resection, the tumor was histologically categorized as an intermediate grade of intramedullary melanocytoma, an uncommon neoplasm. Based on this peculiar case and review of the literature, radical surgical resection appears to be the therapy of choice for intramedullary melanocytomas. However, their high recurrence rate and aggressive behavior suggest the need for close followup with serial MRI.

The GNAQ in the haystack: intramedullary meningeal melanocytoma of intermediate grade at T9-10 in a 58-year-old woman

Meningeal melanocytomas are rare tumors. They are derived from leptomeningeal melanocytes and predominantly occur along the spine and the posterior fossa. Here, the authors report a case of intramedullary melanocytoma of intermediate grade in a 58-year-old female patient who was initially misdiagnosed with malignant melanoma until mutational analyses of a panel of genes associated with melanotic tumors led to reclassification.

Primary melanocytic tumors of the central nervous system: a review with focus on molecular aspects

Primary melanocytic tumors of the central nervous system (CNS) represent a spectrum of rare tumors. They can be benign or malignant and occur in adults as well as in children, the latter often in the context of neurocutaneous melanosis. Until recently, the genetic alterations in these tumors were largely unknown. This is in contrast with cutaneous and uveal melanomas, which are known to harbor distinct oncogenic mutations that can be used as targets for treatment with small-molecule inhibitors in the advanced setting. Recently, novel insights in the molecular alterations underlying primary melanocytic tumors of the CNS were obtained, including different oncogenic mutations in tumors in adult patients (especially GNAQ, GNA11) vs. children (especially NRAS). In this review, the focus is on molecular characteristics of primary melanocytic tumors of the CNS. We summarize what is known about their genetic alterations and discuss implications for pathogenesis and differential diagnosis with other pigmented tumors in or around the CNS. Finally, new therapeutic options with targeted therapy are discussed.

Intracranial malignant melanoma: A report of 7 cases

The aim of the present study was to investigate the clinical diagnosis and treatment of intracranial malignant melanoma. For this purpose, the clinical manifestation, signs, cerebrospinal fluid (CSF) contents, imageology, pathological features, treatment and prognosis of 7 cases of intracranial malignant melanoma were analyzed in The Chinese PLA General Hospital (Beijing, China) from 1996 to 2013. All the melanoma cases were confirmed by histopathology, and CSF cytopathology demonstrated that there were 5 cases of primary malignant melanoma and 2 cases of secondary malignant melanoma. Among the patients, 4 presented with >1 pigmented nevus in the skin, and 1 presented with skin melanoma. Intracranial malignant melanoma mostly affects middle-aged males. CSF cytopathology and imageology (particularly enhanced magnetic resonance), are important tools in the diagnosis of the disease. Particularly, when a patient presents with a pigmented nevus in the skin and an abnormal lesion in the brain, a diagnosis of intracranial malignant melanoma should be considered.

Oncogenic G Protein GNAQ Induces Uveal Melanoma and Intravasation in Mice

GNAQ and GNA11 are heterotrimeric G protein alpha subunits, which are mutated in a mutually exclusive pattern in most cases of uveal melanoma, one of the most aggressive cancers. Here we introduce the first transgenic mouse model of uveal melanoma, which develops cancers induced by expression of oncogenic GNAQ(Q209L) under control of the Rosa26 promoter. Disease penetrance is 100% by 3 months of age, with 94% of mice also developing lung tumors. In this model, the Yap protein of the Hippo pathway is activated in the eyes, and blood vessels near the lesions in the head and lungs exhibit melanocytic invasion. While full transcription levels are not necessary for GNAQ(Q209L) to transform mouse melanocytes, we obtained suggestive evidence of a selective advantage for increased GNAQ(Q209L) expression in human tumors. Intriguingly, enforced expression of GNAQ(Q209L) progressively eliminated melanocytes from the interfollicular epidermis in adults, possibly explaining the near absence of GNAQ(Q209) mutations in human epithelial melanomas. The mouse model also exhibited dermal nevi and melanocytic neoplasms of the central nervous system, accompanied by impaired hearing and balance, identifying a novel role for GNAQ in melanocyte-like cells of the inner ear. Overall, this model offers a new tool to dissect signaling by oncogenic GNAQ and to test potential therapeutics in an in vivo setting where GNAQ(Q209L) mutations contribute to both the initiation and metastatic progression of uveal melanoma.

Genomic Classification of Cutaneous Melanoma

We describe the landscape of genomic alterations in cutaneous melanomas through DNA, RNA, and protein-based analysis of 333 primary and/or metastatic melanomas from 331 patients. We establish a framework for genomic classification into one of four subtypes based on the pattern of the most prevalent significantly mutated genes: mutant BRAF, mutant RAS, mutant NF1, and Triple-WT (wild-type). Integrative analysis reveals enrichment of KIT mutations and focal amplifications and complex structural rearrangements as a feature of the Triple-WT subtype. We found no significant outcome correlation with genomic classification, but samples assigned a transcriptomic subclass enriched for immune gene expression associated with lymphocyte infiltrate on pathology review and high LCK protein expression, a T cell marker, were associated with improved patient survival. This clinicopathological and multi-dimensional analysis suggests that the prognosis of melanoma patients with regional metastases is influenced by tumor stroma immunobiology, offering insights to further personalize therapeutic decision-making.

Consistent copy number changes and recurrent PRKAR1A mutations distinguish Melanotic Schwannomas from Melanomas: SNP-array and next generation sequencing analysis

Melanotic Schwannomas (MS) are rare tumors that share histological features with melanocytic tumors and schwannomas. However, their genetics are poorly understood. To elucidate the genetic characteristics of MS, we performed genome-wide studies in a series of cases. Twelve MS cases were available for the study. Genomic DNAs extracted from formalin-fixed paraffin embedded tumor tissues were subjected to copy number (CN) and allelic imbalance (AI) analysis by Single Nucleotide Polymorphism (SNP)-array and screened for mutations in coding exons of 341 key cancer-associated genes using a hybrid capture-based next-generation sequencing (NGS) assay. Sanger sequencing was used to further verify recurrent mutations detected by NGS study. SNP-array analysis revealed remarkably stereotypic chromosomal abnormalities in MS. Hypodiploidy was common, typically involving monosomies of chromosomes 1, 2, and 17. All 12 samples showed mutations in PRKAR1A gene, including 2 cases with 2 mutations each. The 14 mutations were scattered across PRKAR1A, and most were inactivating mutations. AI on 17q, presenting as loss of heterozygosity with or without CN losses, combined with a PRKAR1A mutation was observed in 9/12 MS cases. The remaining 3 cases included the two samples harboring two mutations in PRKAR1A. MS exhibits a stereotypic pattern of chromosomal losses. In contrast, melanomas are typically characterized by the presence of multiple CN aberrations, without demonstrable differences in the frequency of losses and gains. Inactivation of both alleles of PRKAR1A by "two hits" observed in almost all cases underscores the central role of PRKAR1A in the pathogenesis of this neoplasm. © 2015 Wiley Periodicals, Inc.

[Primary malignant melanoma of the central nervous system: A diagnostic challenge]

BACKGROUND

The rare incidence of primary malignant melanoma of the central nervous system and its ability to mimic other melanocytic tumors on images makes it a diagnostic challenge for the neurosurgeon.

CLINICAL CASE

A 51-year-old patient, with a tumor located in the right forniceal callosum area. Total surgical excision was performed. Histopathological result was consistent with the diagnosis of primary malignant melanoma of the central nervous system, after ruling out extra cranial and extra spinal melanocytic lesions.

CONCLUSIONS

The primary malignant melanoma of the central nervous system is extremely rare. There are features in magnetic resonance imaging that increase the diagnostic suspicion; nevertheless there are other tumors with more prevalence that share some of these features through image. Since there is not an established therapeutic standard its prognosis is discouraging.

Intermediate-grade meningeal melanocytoma associated with nevus of Ota: a case report and review of the literature

Meningeal melanocytomas are rare melanin-producing tumors that are often found to be benign. However, a small subset of these tumors can present as intermediate-grade melanocytomas (IGMs) that have histopathological features that are between those of benign melanocytomas and malignant melanomas. IGMs have the potential to recur and metastasize or progress to a more histologically high grade melanoma. Melanocytomas appear to differ from primary and metastatic melanoma by their prolonged clinical course and they appear to have different driver mutations (i.e. mutation of GNAQ gene). The association of a meningeal melanocytoma with nevus of Ota is extremely rare. To our knowledge, there have been only 10 reported cases of synchronous occurrence and only one of the cases involved an IGM. We report the second case of intermediate-grade meningeal melanocytoma that is associated with congenital nevus of Ota. Histopathological work-up confirmed the intermediate grade of the lesion and a driver GNAQ mutation was identified consistent with previous reports.

Melanotic tumors of the nervous system are characterized by distinct mutational, chromosomal and epigenomic profiles

Melanotic tumors of the nervous system show overlapping histological characteristics but differ substantially in their biological behavior. In order to achieve a better delineation of such tumors, we performed an in-depth molecular characterization. Eighteen melanocytomas, 12 melanomas, and 14 melanotic and 14 conventional schwannomas (control group) were investigated for methylome patterns (450k array), gene mutations associated with melanotic tumors and copy number variants (CNVs). The methylome fingerprints assigned tumors to entity-specific groups. Methylation groups also showed a substantial overlap with histology-based diagnosis suggesting that they represent true biological entities. On the molecular level, melanotic schwannomas were characterized by a complex karyotype with recurrent monosomy of chromosome 22q and variable whole chromosomal gains and recurrent losses commonly involving chromosomes 1, 17p and 21. Melanocytomas carried GNAQ/11 mutations and presented with CNV involving chromosomes 3 and 6. Melanomas were frequently mutated in the TERT promoter, harbored additional oncogene mutations and showed recurrent chromosomal losses involving chromosomes 9, 10 and 6q, as well as gains of 22q. Together, melanotic nervous system tumors have several distinct mutational and chromosomal alterations and can reliably be distinguished by methylome profiling.

Predictive molecular markers in metastases to the central nervous system: recent advances and future avenues

Metastases to the central nervous system (CNS) are common in several cancer types. For most primary tumors that commonly metastasize to the CNS, molecular biomarker analyses are recommended in the clinical setting for selection of appropriate targeted therapies. Therapeutic efficacy of some of these agents has been documented in patients with brain metastases, and molecular testing of CNS metastases should be considered in the clinical setting. Here, we summarize the clinically relevant biomarker tests that should be considered in neurosurgical specimens based on the current recommendations of the European Society of Medical Oncology (ESMO) or the National Comprehensive Cancer Network (NCCN) for the most relevant primary tumor types: lung cancer (EGFR mutations, ALK rearrangement, BRAF mutations), breast cancer (HER2 amplification, steroid receptor overexpression), melanoma (BRAF mutations), and colorectal cancer (RAS mutations). Furthermore, we discuss emerging therapeutic targets including novel oncogenic alterations (ROS1 rearrangements, FGFR1 amplifications, CMET amplifications, and others) and molecular features of the tumor microenvironment (including immune-checkpoint molecules such as CTLA4 and PD-1/PD-L1). We also discuss the potential role of advanced biomarker tests such as next-generation sequencing and "liquid biopsies" for patients with CNS metastases.

Discovery of new membrane-associated proteins overexpressed in small-cell lung cancer

INTRODUCTION

Small-cell lung cancer (SCLC) is the most aggressive subtype of lung cancer, with no early detection strategy or targeted therapy currently available. We hypothesized that difference gel electrophoresis (DIGE) may identify membrane-associated proteins (MAPs) specific to SCLC, advance our understanding of SCLC biology, and discover new biomarkers of SCLC.

METHODS

MAP lysates were prepared from three SCLCs, three non-small-cell lung cancers, and three immortalized normal bronchial epithelial cell lines and coanalyzed by DIGE. Subsequent protein identification was performed by mass spectrometry. Proteins were submitted to Ingenuity Pathway Analysis. Candidate biomarkers were validated by Western blotting (WB) and immunohistochemistry (IHC).

RESULTS

Principal component analysis on the global DIGE data set demonstrated that the four replicates derived from each of the nine cell lines clustered closely, as did samples within the same histological group. One hundred thirty-seven proteins were differentially expressed in SCLC compared with non-small-cell lung cancer and immortalized normal bronchial epithelial cells. These proteins were overrepresented in cellular/tissue morphology networks. Dihydropyrimidinase-related protein 2, guanine nucleotide-binding protein alpha-q, laminin receptor 1, pontin, and stathmin 1 were selected as candidate biomarkers among MAPs overexpressed in SCLC. Overexpression of all candidates but RSSA in SCLC was verified by WB and/or IHC on tissue microarrays. These proteins were significantly associated with SCLC histology and survival in univariables analyses.

CONCLUSION

DIGE analysis of a membrane-associated subproteome discovered overexpression of dihydropyrimidinase-related protein 2, guanine nucleotide-binding protein alpha-q, RUVB1, and stathmin 1 in SCLC. Results were verified by WB and/or IHC in primary tumors, suggesting that investigating their functional relevance in SCLC progression is warranted. Association with survival requires further validation in larger clinical data sets.

Is it a primary or metastatic melanocytic neoplasm of the central nervous system?: A molecular based approach

Primary melanocytic neoplasms of the central nervous system (CNS) are uncommon and must be distinguished from metastatic lesions as patients with metastatic disease carry a worse prognosis. Therefore, tools to aid in the diagnosis of a primary CNS melanocytic neoplasm would be of clinical utility. Primary CNS melanocytic neoplasms, including uveal melanomas have frequent mutations in GNAQ and GNA11, but are rare in cutaneous and mucosal melanomas. Additionally, primary uveal melanomas often exhibit monosomy 3 conferring an elevated risk of metastasis. We present a 63 year-old male with a melanocytic neoplasm in the thoracic spinal cord. Molecular studies revealed the tumor contained a GNAQ mutation and four-color fluorescent in situ hybridization (FISH) composed of chromosome enumeration probes for 3, 7, 17 and a locus specific probe for 9p21/CDKN2A yielded a normal result (i.e. two copies per cell), favoring a primary versus metastatic melanocytic neoplasm of the CNS. We report a case in which the combination of mutational analysis and FISH aided in identifying the origin of the neoplasm.

Hippo-independent activation of YAP by the GNAQ uveal melanoma oncogene through a trio-regulated rho GTPase signaling circuitry

Mutually exclusive activating mutations in the GNAQ and GNA11 oncogenes, encoding heterotrimeric Gαq family members, have been identified in ∼ 83% and ∼ 6% of uveal and skin melanomas, respectively. However, the molecular events underlying these GNAQ-driven malignancies are not yet defined, thus limiting the ability to develop cancer-targeted therapies. Here, we focused on the transcriptional coactivator YAP, a critical component of the Hippo signaling pathway that controls organ size. We found that Gαq stimulates YAP through a Trio-Rho/Rac signaling circuitry promoting actin polymerization, independently of phospholipase Cβ and the canonical Hippo pathway. Furthermore, we show that Gαq promotes the YAP-dependent growth of uveal melanoma cells, thereby identifying YAP as a suitable therapeutic target in uveal melanoma, a GNAQ/GNA11-initiated human malignancy.

Molecular pathology of malignant melanoma: changing the clinical practice paradigm toward a personalized approach

Melanocytic proliferations are notoriously difficult lesions to evaluate histologically, even among experts, as there is a lack of objective, highly reproducible criteria, which can be broadly applied to the wide range of melanocytic lesions encountered in daily practice. These difficult diagnoses are undeniably further compounded by the substantial medicolegal risks of an "erroneous" diagnosis. Molecular information and classification of melanocytic lesions is already vast and constantly expanding. The application of molecular techniques for the diagnosis of benignity or malignancy is, at times, confusing and limits its utility if not used properly. In addition, current and future therapies will necessitate molecular classification of melanoma into one of several distinct subtypes for appropriate patient-specific therapy. An understanding of what different molecular markers can and cannot predict is of the utmost importance. We discuss both mutational analysis and chromosomal gains/losses to help clarify this continually developing and confusing facet of pathology.

Experimental treatment of NRAS-mutated neurocutaneous melanocytosis with MEK162, a MEK-inhibitor

Neurocutaneous melanosis (NCM) is a rare congenital disorder characterized by the association of large and/or multiple congenital melanocytic nevi (CMN) of the skin with melanocytic lesions of the leptomeninges, including melanocytosis. Leptomeningeal melanocytosis carries a poor prognosis once neurological symptoms develop. Despite surgery, which is often not radical, few other treatment options exist. Recently, it was demonstrated that early embryonic, post-zygotic somatic mutations in the NRAS gene are implicated in the pathogenesis of NCM.

In this report, we present a 13-year-old boy with NCM and progressive symptomatic leptomeningeal melanocytosis. A somatic NRAS^Q61K mutation was present in both CMN as well as the melanocytosis. Despite repeated surgery, the patient showed clinical progression. Therefore, treatment with MEK162, a MEK inhibitor, was started on compassionate use base. The patient died only five days later, i.e. too early to expect a clinical effect of MEK162 therapy. We therefore studied the effect of MEK162 at the protein level in the leptomeningeal tumor by immunohistochemical and Western Blot analyses using Ki67 and pERK antibodies. We observed lower MIB-1 expression and lower pERK expression in the post-treatment samples compared to pre-treatment, suggesting a potential effect of MEK inhibiting therapy. Further studies are needed to determine whether MEK inhibitors can effectively target NRAS-mutated symptomatic NCM, a rare but potentially fatal disease.

Neurocutaneous melanocytosis

Neurocutaneous melanosis or neurocutaneous melanocytosis is a rare sporadic congenital disorder characterized by the presence of giant and/or multiple satellite congenital melanocytic nevi in the skin and benign melanocytic pigmentation of the leptomeninges. These two defining features were recognized more than a century ago. A third characteristic feature is proliferative nodules arising from giant nevi. The etiology is unknown, but neurocutaneous melanosis is considered a developmental disorder of melanocyte precursors from neural crest. The distinctive unique distribution of the congenital giant nevi that gives a "garment" appearance is also an expression of the neural crest. The neurological manifestations often appear in infancy.The special association of neurocutaneous melanosis with Dandy-Walker malformation complex may be explained by a common pathogenesis. Mortality in infancy and childhood is high.

Genetic alterations and personalized medicine in melanoma: progress and future prospects

High-throughput sequencing technologies are providing new insights into the genetic alterations involved in melanomagenesis. It appears likely that most genetic events important in the pathogenesis of melanoma will be discovered over the next few years. Genetic analysis is also increasingly being used to direct patient care. In parallel with the discovery of new genes and the elucidation of molecular pathways important in the development of melanoma, therapies targeting these pathways are becoming available. In other words, the age of personalized medicine has arrived, characterized by molecular profiling of melanoma to identify the relevant genetic alterations and the abnormal signaling mechanisms involved, followed by selection of optimal, individualized therapies. In this review, we summarize the key genetic alterations in melanoma and the development of targeted agents against melanomas bearing specific mutations. These developments in melanoma serve as a model for the implementation of personalized medicine for patients with all cancers.

Metastatic melanoma mimicking solitary fibrous tumor: report of two cases

Malignant melanomas are known for their remarkable morphological variation and aberrant immunophenotype with loss of lineage-specific markers, especially in recurrences and metastases. Hot spot mutations in BRAF, NRAS, GNAQ, and GNA11 and mutations in KIT are oncogenic events in melanomas. Therefore, genotyping can be a useful ancillary diagnostic tool. We present one case each of recurrent and metastatic melanoma, both showing histological and immunohistochemical features of solitary fibrous tumor (SFT). Mutational analysis detected BRAF and NRAS mutations in the primary and secondary lesions, respectively. This result confirmed the diagnosis of recurrent/metastastic melanoma.

Sturge-Weber syndrome coexisting with episodes of rhabdomyolysis

Background

Sturge-Weber syndrome is a congenital neurocutaneous disorder characterized by facial port-wine stain, leptomeningeal angioma, and neurological disorders. Sturge-Weber syndrome can coexist with other disorders in a few patients; however, muscular abnormalities have not been reported in patients with Sturge-Weber syndrome.

Case presentation

A Chinese girl presented with extensive port-wine stains, congenital bilateral glaucoma, and leptomeningeal angiomatosis. The neurocutaneous symptoms were consistent with the diagnostic criteria of Sturge-Weber syndrome. Meanwhile, episodes of rhabdomyolysis were supported by the recurrent symptoms as follows: exercise intolerance, hyperCKmia, elevated serum myoglobin, and renal failure. Myopathological features and high level of blood long-chain acyl-carnitine indicated that episodes of rhabdomyolysis might be caused by lipid metabolic myopathy. Causative mutations were not found in the CPT2, ACADVL, and GNAQ gene.

Conclusions

We report the first case that Sturge-Weber syndrome coexists with episodes of rhabdomyolysis associated with lipid metabolic myopathy.

Primary melanoma of the CNS in children is driven by congenital expression of oncogenic NRAS in melanocytes

NRAS mutations are common in human melanoma. To produce a mouse model of NRAS-driven melanoma, we expressed oncogenic NRAS (NRAS(G12D)) in mouse melanocytes. When NRAS(G12D) was expressed in the melanocytes of developing embryos, it induced melanocyte proliferation and congenital melanocytic lesions reminiscent of human blue nevi but did not induce cutaneous melanoma. Unexpectedly, however, it did induce early-onset primary melanoma of the central nervous system (CNS). The tumors were rapidly proliferating and caused neurologic symptoms, rapid health deterioration, and death. NRAS is not a common driver oncogene of primary melanoma of the CNS in adults, but we report two cases of primary melanoma of the CNS in children, both of which carried oncogenic mutations in NRAS. We conclude that acquisition of somatic mutations in NRAS in CNS melanocytes is a predisposing risk factor for primary melanoma of the CNS in children, and we present a mouse model of this disease.

SIGNIFICANCE

We show that the acquisition of NRAS mutations in melanocytes during embryogenesis is a risk factor for early-onset melanoma of the CNS. We have developed a powerful mouse model to study this rare but devastating childhood disease, and to develop therapeutic approaches for its treatment.

Neoplastic leptomeningitis presenting in a melanoma patient treated with dabrafenib (a V600EBRAF inhibitor): a case report

INTRODUCTION

Leptomeningeal metastases are occurring at higher frequency in cancer patients. The prognosis of leptomeningeal metastases is poor and standard treatment, which includes radiotherapy and chemotherapy, is mostly ineffective. Melanoma represents one of the tumors with the highest incidence of leptomeningeal metastases. For such a disease, the BRAF inhibitors have recently been demonstrated to be effective on melanoma brain metastases harboring the V600EBRAF mutation.

CASE PRESENTATION

We report a case of a 39-year-old Italian woman with advanced melanoma with brain, lung and peritoneum metastases harboring the V600EBRAF mutation. In August 2010 she was enrolled into the BRIM3 trial and after the randomization process she received dacarbazine. After two cycles, there was evidence of disease progression in her peritoneum and lung. For this reason, she was enrolled into another clinical trial with the GSK2118436 BRAF inhibitor, dabrafenib, as a second line of therapy. She had a partial response that was maintained until 13 weeks of treatment. In January 2011 she developed symptoms typical for brain metastases and received a diagnosis of leptomeningeal involvement of melanoma cells after an examination of her cerebral spinal fluid; magnetic resonance imaging was negative for meningitis or brain metastases. Analysis of her cerebral spinal fluid sample confirmed that the melanoma cells still carried the V600EBRAF mutation. After a few days, our patient went into a coma and died.

CONCLUSION

Starting with a clinical case, we discuss the pathogenesis of leptomeningeal metastases and whether the leptomeninges may represent a sanctuary where melanoma cells may generate resistance and/or BRAF inhibitors cannot reach an adequate concentration for significant activity. We assess whether treatment with BRAF inhibitors in melanoma patients should be interrupted as soon as disease progression appears or continued beyond progression, through the administration of additional compounds.

Immunohistochemical testing of BRAF V600E status in 1,120 tumor tissue samples of patients with brain metastases

Brain metastases (BM) are frequent and carry a dismal prognosis. BRAF V600E mutations are found in a broad range of tumor types and specific inhibitors targeting BRAF V600E protein exist. We analyzed tumoral BRAF V600E-mutant protein expression using the novel mutation-specific antibody VE1 in a series of 1,120 tumor specimens (885 BM, 157 primary tumors, 78 extra-cranial metastases) of 874 BM patients. In 85 cases, we performed validation of immunohistochemical results by BRAF exon 15 gene sequencing. BRAF V600E protein was expressed in BM of 42/76 (55.3%) melanomas, 1/15 (6.7%) ovarian cancers, 4/72 (5.5%) colorectal cancers, 1/355 (0.3%) lung cancers, 2/6 thyroid cancers and 1/2 choriocarcinomas. BRAF V600E expression showed high intra-tumoral homogeneity and was similar in different tumor manifestations of individual patients. VE1 immunohistochemistry and BRAF exon 15 sequencing were congruent in 68/70 (97.1%) cases, but VE1 immunostaining identified small BRAF V600E expressing tumor cell aggregates in 10 cases with inconclusive genetic results. Melanoma patients with BRAF V600E mutant protein expressing tumors were significantly younger at diagnosis of the primary tumor and at operation of BM than patients with non-mutated tumors. In conclusion, expression of BRAF V600E mutant protein occurs in approximately 6% of BM and is consistent in different tumor manifestations of the same patient. Thus, BRAF V600E inhibiting therapies seem feasible in selected BM patients. Immunohistochemical visualization of V600E-mutant BRAF protein is a promising tool for patient stratification. An integrated approach combining both, VE1 immunohistochemistry and genetic analysis may increase the diagnostic accuracy of BRAF mutation analysis.

New strategies in melanoma: molecular testing in advanced disease

Melanoma is one of the most aggressive forms of skin cancer. The management of melanoma is evolving rapidly due to an improved understanding of the molecular heterogeneity of this disease and the development of effective, personalized, targeted therapy strategies. Although previous classification systems were based predominantly on clinical and histologic criteria, there is now a strong rationale for adding molecular markers to the diagnostic evaluation of these tumors. Research has shown that the types and prevalence of genetic alterations vary among melanoma subtypes. Thus, rational molecular testing should be based on an understanding of the events that are likely to occur in a given tumor and the clinical implications of test results. This review summarizes the existing data that support the rationale for molecular testing in clinically defined melanoma subtypes. Emerging challenges and controversies regarding the use of various molecular testing platforms, and their implications for clinical testing, are also discussed.

P-Rex1 is required for efficient melanoblast migration and melanoma metastasis

Metastases are the major cause of death from melanoma, a skin cancer that has the fastest rising incidence of any malignancy in the Western world. Molecular pathways that drive melanoblast migration in development are believed to underpin the movement and ultimately the metastasis of melanoma. Here we show that mice lacking P-Rex1, a Rac-specific Rho GTPase guanine nucleotide exchange factor, have a melanoblast migration defect during development evidenced by a white belly. Moreover, these P-Rex1(-/-) mice are resistant to metastasis when crossed to a murine model of melanoma. Mechanistically, this is associated with P-Rex1 driving invasion in a Rac-dependent manner. P-Rex1 is elevated in the majority of human melanoma cell lines and tumour tissue. We conclude that P-Rex1 has an important role in melanoblast migration and cancer progression to metastasis in mice and humans.

The melanomas: a synthesis of epidemiological, clinical, histopathological, genetic, and biological aspects, supporting distinct subtypes, causal pathways, and cells of origin

Converging lines of evidence from varied scientific disciplines suggest that cutaneous melanomas comprise biologically distinct subtypes that arise through multiple causal pathways. Understanding the respective relationships of each subtype with etiologic factors such as UV radiation and constitutional factors is the first necessary step toward developing refined prevention strategies for the specific forms of melanoma. Furthermore, classifying this disease precisely into biologically distinct subtypes is the key to developing mechanism-based treatments, as highlighted by recent discoveries. In this review, we outline the historical developments that underpin our understanding of melanoma heterogeneity, and we do this from the perspectives of clinical presentation, histopathology, epidemiology, molecular genetics, and developmental biology. We integrate the evidence from these separate trajectories to catalog the emerging major categories of melanomas and conclude with important unanswered questions relating to the development of melanoma and its cells of origin.

Mutations in GNA11 in uveal melanoma

BACKGROUND

Uveal melanoma is the most common intraocular cancer. There are no effective therapies for metastatic disease. Mutations in GNAQ, the gene encoding an alpha subunit of heterotrimeric G proteins, are found in 40% of uveal melanomas.

METHODS

We sequenced exon 5 of GNAQ and GNA11, a paralogue of GNAQ, in 713 melanocytic neoplasms of different types (186 uveal melanomas, 139 blue nevi, 106 other nevi, and 282 other melanomas). We sequenced exon 4 of GNAQ and GNA11 in 453 of these samples and in all coding exons of GNAQ and GNA11 in 97 uveal melanomas and 45 blue nevi.

RESULTS

We found somatic mutations in exon 5 (affecting Q209) and in exon 4 (affecting R183) in both GNA11 and GNAQ, in a mutually exclusive pattern. Mutations affecting Q209 in GNA11 were present in 7% of blue nevi, 32% of primary uveal melanomas, and 57% of uveal melanoma metastases. In contrast, we observed Q209 mutations in GNAQ in 55% of blue nevi, 45% of uveal melanomas, and 22% of uveal melanoma metastases. Mutations affecting R183 in either GNAQ or GNA11 were less prevalent (2% of blue nevi and 6% of uveal melanomas) than the Q209 mutations. Mutations in GNA11 induced spontaneously metastasizing tumors in a mouse model and activated the mitogen-activated protein kinase pathway.

CONCLUSIONS

Of the uveal melanomas we analyzed, 83% had somatic mutations in GNAQ or GNA11. Constitutive activation of the pathway involving these two genes appears to be a major contributor to the development of uveal melanoma. (Funded by the National Institutes of Health and others.).

Improved discrimination of melanotic schwannoma from melanocytic lesions by combined morphological and GNAQ mutational analysis

The histological differential diagnosis between melanotic schwannoma, primary leptomeningeal melanocytic lesions and cellular blue nevus can be challenging. Correct diagnosis of melanotic schwannoma is important to select patients who need clinical evaluation for possible association with Carney complex. Recently, we described the presence of activating codon 209 mutations in the GNAQ gene in primary leptomeningeal melanocytic lesions. Identical codon 209 mutations have been described in blue nevi. The aims of the present study were to (1) perform a histological review of a series of lesions (initially) diagnosed as melanotic schwannoma and analyze them for GNAQ mutations, and (2) test the diagnostic value of GNAQ mutational analysis in the differential diagnosis with leptomeningeal melanocytic lesions. We retrieved 25 cases that were initially diagnosed as melanotic schwannoma. All cases were reviewed using established criteria and analyzed for GNAQ codon 209 mutations. After review, nine cases were classified as melanotic schwannoma. GNAQ mutations were absent in these nine cases. The remaining cases were reclassified as conventional schwannoma (n = 9), melanocytoma (n = 4), blue nevus (n = 1) and lesions that could not be classified with certainty as melanotic schwannoma or melanocytoma (n = 2). GNAQ codon 209 mutations were present in 3/4 melanocytomas and the blue nevus. Including results from our previous study in leptomeningeal melanocytic lesions, GNAQ mutations were highly specific (100%) for leptomeningeal melanocytic lesions compared to melanotic schwannoma (sensitivity 43%). We conclude that a detailed analysis of morphology combined with GNAQ mutational analysis can aid in the differential diagnosis of melanotic schwannoma with leptomeningeal melanocytic lesions.