SF3B1 and BAP1 mutations in blue nevus-like melanoma

Genetic re-classification of combined hepatocellular-cholangiocarcinoma and small duct type intrahepatic cholangiocarcinoma

BACKGROUND

Combined hepatocellular-cholangiocarcinoma (cHCC-CCA) shares various features with small duct type intrahepatic cholangiocarcinoma (SmD-iCCA) and sometimes histological diagnosis may be difficult.

METHODS

We examined genetic alterations such as hTERT promoter (hTERT), p53, and fibroblast growth factor receptor 2 (FGFR2) in 103 PLCs diagnosed as cHCC-CCA or SmD-iCCA. A cluster analysis was performed on the R software for re-classification of PLCs including cHCC-CCA and SmD-iCCA.

RESULTS

The primary liver carcinomas (PLCs) were divided into 5 clusters; 19 tumors (18 %) in Cluster-1 (with alterations in hTERT and/or p53), 24 (23 %) in Cluster-2 (FGFR2 and/or p53), 13 (13 %) in Cluster-3 (IDH2 or null), 19 (18 %) in Cluster-4 (MTAP and/or FGFR2), 28 (27 %) in Cluster-5 (ARID1A and/or PBRM1), being based on genetic alterations. Cluster-1 and Clusters-2 to- 5 formed distinct 2 groups. Cluster-1 was characterized by significantly bigger size, rich and higher histological grade of HCC component, significantly less cholangiolocellular carcinoma (CLC)-component, ductal plate malformation pattern and bile duct adenoma in the background livers. No SmD-iCCA was included in Cluster-1, whereas SmD-iCCA distributed evenly in Clusters 2-5. Cluster-4 was characterized by higher prevalence of hepatitis B and higher histological diversity scores.

CONCLUSION

PLCs diagnosed as cHCC-CCA or SmD-iCCAs could be divided into 5 clusters based on genetic alterations. Cluster-1 was HCC-like cluster characterized by hTERT alteration, rich and higher grade of HCC and bigger size. Clusters-2-5 may be iCCA-like clusters characterized by different genetic alterations. cHCC-CCA in Cluster-1 and Clusters-2-5 may be handled separately for further analysis and treatment.

Clinicopathologic Features, Management, and Outcomes Of Pediatric CRTC1::TRIM11 and MED15::ATF1 Tumors With Spitzoid Morphology: A Case Series

Limited information is available on the clinicopathologic features and management of pediatric CRTC1::TRIM11 (CTRTs) and MED15::ATF1-rearranged tumors (MARTs). In this series of pediatric CTRTs (n = 5) and MARTs (n = 2), all tumors exhibited spitzoid morphology and expressed melanocytic markers. Metastatic progression occurred in one CTRT and two MARTs: all three received immunotherapy, resulting in disease control in two patients and one death due to progressive disease. A fourth individual had lymph node micrometastasis that remained stable without progression. This case series highlights the potentially aggressive behavior of these tumors and suggests that immunotherapy may be an effective treatment option for advanced disease.

Malignant blue melanoma

Malignant blue melanomas arise from blue nevi and all related intradermal melanocytic proliferations. They harbor specific, mutually exclusive mutations in the G-coupled protein pathway, mainly involving GNAQ or GNA11. Other rare genetic drivers include CYSLTR2 or PCLB4 mutations. PKC and GRM1-gene fusions have been recently added to this list. Malignant blue melanomas have a predilection for the scalp area, presenting as rapidly growing nodules within a pre-existing lesion. Histopathologically, these tumors are located in the dermis and subcutaneous fat and consist of large nodules or expanding dense sheets. Tumor necrosis is commonly seen. Large spindle-shaped and epithelioid melanocytes with high-grade cytologic atypia and frequent mitotic figures are at higher magnification. A benign blue nevus or intermediate-grade blue melanocytoma is frequently found on the side of the central mass. Loss of nuclear BAP1 immunoreactivity is a poor prognostic factor.

Blue Nevus-Like Metastatic Melanoma in a Patient With Primary Lentigo Maligna Melanoma

Metastatic melanoma with unusual histopathology can be diagnostically challenging. One exceptionally rare cutaneous manifestation of metastases is blue-nevus-like metastatic melanoma (BNLMM). A 74-year-old male presented with a blue-gray lesion on his left helix in the same anatomical region of a previously resected lentigo maligna. Histopathological sections demonstrated an atypical biphasic proliferation of dendritic melanocytes with pigment incontinence and epidermal sparing, measuring > 0.05 mm in diameter. Although the majority of the cell population exhibited cytologic features consistent with a blue nevus, there was a subset of dendritic cells with irregular epithelioid contours and rare, typical dermal mitotic figures. Sections showed an increased Mart-1/Ki67 rate. Perineural and angiotropic involvement by the atypical melanocytes was identified. Immunohistochemical (IHC) stains for SOX-10, HMB45, and PRAME highlighted melanocytic proliferation. BAP-1 IHC was retained, and p16 IHC showed complete loss. No previous procedure site changes were present, indicating that the dendritic cell proliferation was separated from the primary invasive melanoma by normal dermis. The histopathological and immunohistochemical findings led to a diagnosis of microsatellite BNLMM. We report this case to highlight the importance of this rare entity and to avoid misdiagnosis of BNLMM, which would significantly impact patient prognosis, treatment, follow-up, and outcomes.

Evaluation and Surgical Management of Pediatric Cutaneous Melanoma and Atypical Spitz and Non-Spitz Melanocytic Tumors (Melanocytomas): A Report From Children's Oncology Group

PURPOSE

The purpose of this study was to develop recommendations for the diagnostic evaluation and surgical management of cutaneous melanoma (CM) and atypical Spitz tumors (AST) and non-Spitz melanocytic tumors (melanocytomas) in pediatric (age 0-10 years) and adolescent (age 11-18 years) patients.

METHODS

A Children's Oncology Group-led panel with external, multidisciplinary CM specialists convened to develop recommendations on the basis of available data and expertise.

RESULTS

Thirty-three experts from multiple specialties (cutaneous/medical/surgical oncology, dermatology, and dermatopathology) established recommendations with supporting data from 87 peer-reviewed publications.

RECOMMENDATIONS

(1) Excisional biopsies with 1-3 mm margins should be performed when feasible for clinically suspicious melanocytic neoplasms. (2) Definitive surgical treatment for CM, including wide local excision and sentinel lymph node biopsy (SLNB), should follow National Comprehensive Cancer Network Guidelines in the absence of data from pediatric-specific surgery trials and/or cohort studies. (3) Accurate classification of ASTs as benign or malignant is more likely with immunohistochemistry and next-generation sequencing. (4) It may not be possible to classify some ASTs as likely/definitively benign or malignant after clinicopathologic and/or molecular correlation, and these Spitz tumors of uncertain malignant potential should be excised with 5 mm margins. (5) ASTs favored to be benign should be excised with 1- to 3-mm margins if transected on biopsy. (6) Re-excision is not necessary if the AST does not extend to the biopsy margin(s) when complete/excisional biopsy was performed. (7) SLNB should not be performed for Spitz tumors unless a diagnosis of CM is favored on clinicopathologic evaluation. (8) Non-Spitz melanocytomas have a presumed increased risk for progression to CM and should be excised with 1- to 3-mm margins if transected on biopsy. (9) Re-excision of non-Spitz melanocytomas is not necessary if the lesion is completely excised on biopsy.

Heterogeneous pathogenesis of melanoma: BRAF mutations and beyond

Melanoma pathogenesis, conventionally perceived as a linear accumulation of molecular changes, discloses substantial heterogeneity driven by non-linear biological processes, including the direct transformation of melanocyte stem cells. This heterogeneity manifests in diverse biological phenotypes and developmental states, influencing variable responses to treatments. Unveiling the aberrant mechanisms steering melanoma initiation, progression, and metastasis is imperative. Beyond mutations in oncogenic and tumor suppressor genes, the involvement of distinct molecular pathways assumes a pivotal role in melanoma pathogenesis. Ultraviolet (UV) radiations, a principal factor in melanoma etiology, categorizes melanomas based on cumulative sun damage (CSD). The genomic landscape of lesions correlates with UV exposure, impacting mutational load and spectrum of mutations. The World Health Organization's 2018 classification underscores the interplay between sun exposure and genomic characteristics, distinguishing melanomas associated with CSD from those unrelated to CSD. The classification elucidates molecular features such as tumor mutational burden and copy number alterations associated with different melanoma subtypes. The significance of the mutated BRAF gene and its pathway, notably BRAFV600 variants, in melanoma is paramount. BRAF mutations, prevalent across diverse cancer types, present therapeutic avenues, with clinical trials validating the efficacy of targeted therapies and immunotherapy. Additional driver mutations in oncogenes further characterize specific melanoma pathways, impacting tumor behavior. While histopathological examination remains pivotal, challenges persist in molecularly classifying melanocytic tumors. In this review, we went through all molecular characterization that aid in discriminating common and ambiguous lesions. Integration of highly sensitive molecular diagnostic tests into the diagnostic workflow becomes indispensable, particularly in instances where histology alone fails to achieve a conclusive diagnosis. A diagnostic algorithm based on different molecular features inferred by the various studies is here proposed.

Utility of next-generation sequencing in the diagnosis of metastatic melanoma: A case report

During routine dermatologic examination, a 77-year-old male was noted to have a firm blue subcutaneous nodule on his right lateral upper back. His past medical history included metastatic melanoma of unknown primary involving right and left axillary lymph nodes, treated with ipilimumab/nivolumab with complete response, and subsequent primary uveal melanoma. The subcutaneous nodule was located near his previous right axillary scar for metastatic melanoma. Excision of the nodule showed a plexiform neoplasm involving mid and deep dermis composed of spindle and epithelioid atypical cells admixed with numerous melanophages. Central necrosis was present. Immunohistochemical studies revealed the tumor cells to be diffusely positive for HMB45, with retained expression of BAP1 and p16. The tumor cells were negative for PRAME, nuclear expression of β-catenin, LEF1, and BRAF V600E. Molecular studies demonstrated BAP1 and GNA11 somatic mutations, a profile different from that exhibited by his prior melanoma. Collectively, these data were interpreted as a metastasis from uveal melanoma and not a recurrence of his metastatic likely cutaneous melanoma after complete response to immunotherapy. This case emphasizes the importance of molecular studies for definitive diagnosis in challenging clinical situations, especially when there is discordance among histopathological, immunohistochemical, and molecular studies. Integration of clinical, histopathological, and molecular features is warranted.

Beyond typical histology of BAP1-inactivated melanocytoma

BAP1-inactivated melanocytoma (BIM) is a novel subgroup of melanocytic neoplasm listed in the 5th edition of WHO classification of skin tumor. BIM is characterized by two molecular alterations, including a mitogenic driver mutation (usually BRAF gene) and the loss of function of BAP1, a tumor suppressor gene located on chromosome 3p21, which encodes for BRCA1-associated protein (BAP1). The latter represents a nuclear-localized deubiquitinase involved in several cellular processes including cell cycle regulation, chromatin remodeling, DNA damage response, differentiation, senescence and cell death. BIMs are histologically characterized by a population of large epithelioid melanocytes with well-demarcated cytoplasmic borders and copious eosinophilic cytoplasm, demonstrating loss of BAP1 nuclear expression by immunohistochemistry. Recently, we have published a series of 50 cases, extending the morphological spectrum of the neoplasm and highlighting some new microscopic features. In the current article, we focus on some new histological features, attempting to explain and link them to certain mechanisms of tumor development, including senescence, endoreplication, endocycling, asymmetric cytokinesis, entosis and others. In light of the morphological and molecular findings observed in BIM, we postulated that this entity unmasks a fine mechanism of tumor in which both clonal/stochastic and hierarchical model can be unified.

Clinical and genetic characteristics of BAP1-mutated non-uveal and uveal melanoma

Background

Screening for gene mutations has become routine clinical practice across numerous tumor entities, including melanoma. BAP1 gene mutations have been identified in various tumor types and acknowledged as a critical event in metastatic uveal melanoma, but their role in non-uveal melanoma remains inadequately characterized.

Methods

A retrospective analysis of all melanomas sequenced in our department from 2014-2022 (n=2650) was conducted to identify BAP1 mutated samples. Assessment of clinical and genetic characteristics was performed as well as correlations with treatment outcome.

Results

BAP1 mutations were identified in 129 cases and distributed across the entire gene without any apparent hot spots. Inactivating BAP1 mutations were more prevalent in uveal (55%) compared to non-uveal (17%) melanomas. Non-uveal BAP1 mutated melanomas frequently exhibited UV-signature mutations and had a significantly higher mutation load than uveal melanomas. GNAQ and GNA11 mutations were common in uveal melanomas, while MAP-Kinase mutations were frequent in non-uveal melanomas with NF1, BRAF V600 and NRAS Q61 mutations occurring in decreasing frequency, consistent with a strong UV association. Survival outcomes did not differ among non-uveal melanoma patients based on whether they received targeted or immune checkpoint therapy, or if their tumors harbored inactivating BAP1 mutations.

Conclusion

In contrast to uveal melanomas, where BAP1 mutations serve as a significant prognostic indicator of an unfavorable outcome, BAP1 mutations in non-uveal melanomas are primarily considered passenger mutations and do not appear to be relevant from a prognostic or therapeutic perspective.

Expression of fibroblast growth factor receptor 2 (FGFR2) in combined hepatocellular-cholangiocarcinoma and intrahepatic cholangiocarcinoma: clinicopathological study

Genetic alterations including fusions in fibroblast growth factor receptor 2 (FGFR2) are detected in 10-20% of intrahepatic cholangiocarcinoma (iCCA), and FGFR2 inhibitors are effective for the treatment of iCCA. We examined a prevalence of FGFR2 genetic alterations and their clinicopathological significance in combined hepatocellular-cholangiocarcinoma (cHCC-CCA). FGFR2 expression, which is a surrogate marker for FGFR2 genetic alterations, was immunohistochemically assessed in the liver sections from 75 patients with cHCC-CCA, 35 with small duct-type iCCA, 30 with large duct-type iCCA, and 35 with hepatocellular carcinoma (HCC). FGFR2 genetic alterations were detected by reverse transcription-PCR and direct sequence. An association of FGFR2 expression with clinicopathological features was investigated in cHCC-CCAs. FGFR2 expression was detected in significantly more patients with cHCC-CCA (21.3%) and small duct-type iCCA (25.7%), compared to those with large duct-type iCCA (3.3%) and HCC (0%) (p < 0.05). FGFR2-positive cHCC-CCAs were significantly smaller size (p < 0.05), with more predominant cholangiolocarcinoma component (p < 0.01) and less nestin expression (p < 0.05). Genetic alterations of ARID1A and BAP1 and multiple genes were significantly more frequent in FGFR2-positive cHCC-CCAs (p < 0.05). 5'/3' imbalance in FGFR2 genes indicating exon18-truncated FGFR2 was significantly more frequently detected in FGFR2-positive cHCC-CCAs and small duct iCCAs, compared to FGFR2-negative ones (p < 0.05). FGFR2::BICC fusion was detected in a case of cHCC-CCAs. FGFR2 genetic alterations may be prevalent in cHCC-CCAs as well as small duct-type iCCAs, which suggest cHCC-CCAs may also be a possible therapeutic target of FGFR2 inhibitors.

Transactivation of Met signaling by oncogenic Gnaq drives the evolution of melanoma in Hgf-Cdk4 mice

Recent pan-cancer genomic analyses have identified numerous oncogenic driver mutations that occur in a cell-type and tissue-specific distribution. For example, oncogenic mutations in Braf and Nras genes arise predominantly in melanocytic neoplasms of the epidermis, while oncogenic mutations in Gnaq/11 genes arise mostly in melanocytic lesions of the dermis or the uvea. The mechanisms promoting cell-type and tissue-specific oncogenic events currently remain poorly understood. Here, we report that Gnaq/11 hotspot mutations occur as early oncogenic drivers during the evolution of primary melanomas in Hgf-Cdk4 mice. Additional single base substitutions in the Trp53 gene and structural chromosomal aberrations favoring amplifications of the chromosomal region containing the Met receptor gene accumulate during serial tumor transplantation and in cell lines established in vitro. Mechanistically, we found that the GnaqQ209L mutation transactivates the Met receptor. Overexpression of oncogenic GnaqQ209L in the immortalized melanocyte cell line promoted in vivo growth that was enhanced by transgenic Hgf expression in the tumor microenvironment. This cross-signaling mechanism explains the selection of oncogenic Gnaq/11 in primary Hgf-Cdk4 melanomas and provides an example of how oncogenic driver mutations, intracellular signaling cascades, and microenvironmental cues cooperate to drive cancer development in a tissue-specific fashion.

The clinico-pathological spectrum of plaque-type blue naevi and their potential for malignant transformation

AIMS

Plaque-type blue naevi are rare melanocytic tumours presenting as large, pigmented plaques at birth or during childhood. There is a risk for malignant transformation, but no larger comprehensive studies exist and the diagnosis is challenging, especially on limited biopsy material. The aim is to describe the clinicopathological features and behaviour of the disease more comprehensively.

METHODS AND RESULTS

We retrieved eight plaque-type blue naevi, presenting as large, pigmented plaques (median = 7 cm; range = 3-26) most frequently affecting the scalp (four) followed by the cheek, arm, abdominal wall and gluteal cleft (one each), with a slight female predilection. Median age at time of biopsy was 39.5 years (range = 15-90), but three tumours had been present at birth and one since childhood. Histopathologically, the tumours were poorly circumscribed and composed of cellular fascicles of uniform spindle cells in a background of variably prominent pigmented dendritic cells affecting dermis and subcutaneous tissues. The majority had mutations in GNAQ. One tumour showed malignant transformation, characterised by an expansile nodule of pleomorphic epithelioid melanocytes with rhabdoid morphology, high mitotic activity and areas of necrosis. This patient developed metastatic melanoma to lymph nodes. All patients are alive with a median follow-up of 60 months.

CONCLUSION

Plaque-type blue naevi are diagnostically challenging tumours with risk for malignant transformation. Awareness and familiarity with the salient clinicopathological features are necessary for reliable diagnosis, and long-term clinical follow-up is required to monitor for malignant transformation.

Melanoma biology and treatment: a review of novel regulated cell death-based approaches

The incidence of melanoma, the most lethal form of skin cancer, has increased due to ultraviolet exposure. The treatment of advanced melanoma, particularly metastatic cases, remains challenging with poor outcomes. Targeted therapies involving BRAF/MEK inhibitors and immunotherapy based on anti-PD1/anti-CTLA4 antibodies have achieved long-term survival rates of approximately 50% for patients with advanced melanoma. However, therapy resistance and inadequate treatment response continue to hinder further breakthroughs in treatments that increase survival rates. This review provides an introduction to the molecular-level pathogenesis of melanoma and offers an overview of current treatment options and their limitations. Cells can die by either accidental or regulated cell death (RCD). RCD is an orderly cell death controlled by a variety of macromolecules to maintain the stability of the internal environment. Since the uncontrolled proliferation of tumor cells requires evasion of RCD programs, inducing the RCD of melanoma cells may be a treatment strategy. This review summarizes studies on various types of nonapoptotic RCDs, such as autophagy-dependent cell death, necroptosis, ferroptosis, pyroptosis, and the recently discovered cuproptosis, in the context of melanoma. The relationships between these RCDs and melanoma are examined, and the interplay between these RCDs and immunotherapy or targeted therapy in patients with melanoma is discussed. Given the findings demonstrating melanoma cell death in response to different stimuli associated with these RCDs, the induction of RCD shows promise as an integral component of treatment strategies for melanoma.

Diagnosing Cutaneous Melanocytic Tumors in the Molecular Era: Updates and Review of Literature

Over the past decade, molecular and genomic discoveries have experienced unprecedented growth, fundamentally reshaping our comprehension of melanocytic tumors. This review comprises three main sections. The first part gives an overview of the current genomic landscape of cutaneous melanocytic tumors. The second part provides an update on the associated molecular tests and immunohistochemical stains that are helpful for diagnostic purposes. The third section briefly outlines the diverse molecular pathways now utilized for the classification of cutaneous melanomas. The primary goal of this review is to provide a succinct overview of the molecular pathways involved in melanocytic tumors and demonstrate their practical integration into the realm of diagnostic aids. As the molecular and genomic knowledge base continues to expand, this review hopes to serve as a valuable resource for healthcare professionals, offering insight into the evolving molecular landscape of cutaneous melanocytic tumors and its implications for patient care.

GRM1 Gene Fusions as an Alternative Molecular Driver in Blue Nevi and Related Melanomas

Activating mutations in GNAQ, GNA11, CYSLTR2, and PLCB4 genes are regarded as the main oncogenic drivers of blue nevi (BN) and blue malignant melanocytic tumors. Here we report 4 cases of blue melanocytic neoplasms devoid of these mutations but harboring GRM1 gene fusions. In this short series, there was no gender predominance (sex ratio, 1). The mean age at diagnosis was 40 years (range, 12-72). Tumors were located on the face (n = 2), forearm (n = 1), and dorsum of the foot (n = 1). Clinically, a plaque-like pre-existing BN was found in 2 cases, including a deep location; another case presented as an Ota nevus. Two cases were diagnosed as melanoma ex-BN, one as an atypical BN, and one as a plaque-like BN. Microscopic examination revealed a dermal proliferation of dendritic melanocytes in a sclerotic stroma. A dermal cellular nodule with atypia and mitotic activity was observed in 3 cases. Genetic investigation by whole exome RNA sequencing revealed MYO10::GRM1 (n = 2) and ZEB2::GRM1 (n = 1) fusions. A GRM1 rearrangement was identified by fluorescence in situ hybridization in the remaining case. SF3B1 comutations were present in the 2 melanomas, and both had a MYO10::GRM1 fusion. Array comparative genomic hybridization was feasible for 3 cases and displayed multiple copy number alterations in the 2 melanomas and limited copy number alterations in the atypical BN, all genomic profiles compatible with those of classical blue lesions. GRM1 was overexpressed in all cases compared with a control group of blue lesions with other typical mutations. Both melanomas rapidly developed visceral metastases following diagnosis, with a fatal outcome in one case and tumor progression under palliative care in the other. These data suggest that GRM1 gene fusions could represent an additional rare oncogenic driver in the setting of BN, mutually exclusive of classical canonical mutations, especially in plaque-type or Ota subtypes.

[Translated article] Melanoma Arising in Plaque-Type Blue Nevus and Dermal Melanocytosis: Diagnostic and Prognostic Value of BAP1

Melanoma arising in blue nevus, also known as melanoma ex blue nevus, is a specific form of melanoma whose genetic profile is different to that of other cutaneous melanomas and surprisingly similar to that of uveal melanoma. Although melanoma ex blue nevus can appear de novo, it usually arises in a pre-existing blue nevus or dermal melanocytosis. Not all nodular lesions arising in association with blue nevus or dermal melanocytosis are melanomas, however, and because clinical and histologic findings may be insufficient for a definitive diagnosis, additional studies such as comparative genomic hybridization are important. Detection of chromosomal aberrations supports a diagnosis of malignancy. Studies of the BAP1 gene are particularly useful in this setting because loss of expression is indicative of melanoma. We present 3 cases on the spectrum of blue nevus to melanoma ex blue nevus that were studied using molecular biology techniques.

Histopathologic and molecular characterization of BAP-1-inactivated melanoma

BACKGROUND

BRCA1-associated protein 1 (BAP-1) is a deubiquitylase that functions as a tumor suppressor, regulating multiple cellular processes including cell cycle control, differentiation, cell death, and DNA repair. BAP-1-inactivated melanocytic tumors (BIMTs) have recently been described and are characterized by epithelioid cytomorphology, are often clonal in appearance, and typically do not recur or show malignant transformation on follow-up.

AIM

To describe the histopathologic and molecular characterization of five cases of BAP-1-inactivated cutaneous malignant melanomas.

METHODS

The archives at two separate institutions were retrospectively searched for tumors classified as melanoma with loss of BAP-1 via immunohistochemistry. Five cases were identified. These cases were classified as malignant melanoma based on cytomorphology, immunohistochemistry, and ancillary molecular testing. The clinical demographics were recorded, along with the histomorphologic features of each case. Genomic analysis for all cases was performed via OncoScan.

RESULTS

The five reviewed cases consisted of two females and three males ranging from 67 to 74 years in age. Molecular characterization of each case was performed using OncoScan. Microarray assay showed that there was a complete deletion of 3p in all cases, BRAF V600E mutation in two cases, NRAS missense variant in one case, and loss of 9p in three cases. All cases showed malignant copy number alterations.

CONCLUSIONS

Herein we describe five cases of BAP-1-inactivated melanomas confirmed by histomorphology and immunohistochemistry, all of which show malignant copy number profiles including loss of 3p. In addition, we provide a case of a likely BIMT showing progression to BAP-1-inactivated melanoma on a 16-year follow-up.

Blue naevi and the blue tumour spectrum

Blue naevi (BN) form a wide group of benign dermal melanocytic proliferations. They are genetically distinct from common and Spitz naevi with frequent hotspot mutations occurring in Gαq genes. Clinically, BN display a female predominance, elective sites of emergence and a great variety of subtypes related to specific regions of the skin linked to early embryological genetic events. Histologically, most BN are located in the dermis with small, bland, spindled and dendritic pigmented melanocytes within a fibrous background. Variation in tumour volume, fibrosis, and melanin pigment load can be broad. A growth in size and cellularity can occur within a subset of tumours as they acquire the morphological features of cellular blue naevi, with a biphasic architecture associating a dendritic blue naevus morphology near the surface, and deep vertical cellular expansions of medium-sized, bland melanocytes often reaching the subcutis. Sclerosing and myxoid variants can be observed either as individual or combined modifications that can add complexity to an otherwise straightforward diagnosis. Malignant progression of a cellular blue naevus is exceptional with an intermediate stage named atypical cellular blue naevus. Malignant blue melanomas are fast growing, large, pigmented tumours with most often obvious features of malignancy. However, they are difficult to separate from other malignant dermal melanocytic proliferations. Herein, we will extensively detail and illustrate the clinical, histological and genetic features of the vast spectrum of blue naevi and related entities in the skin.

Genetic and methylation profiles distinguish benign, malignant and spitzoid melanocytic tumors

Accurate classification of melanocytic tumors is important for prognostic evaluation, treatment and follow-up protocols of patients. The majority of melanocytic proliferations can be classified solely based on clinical and pathological criteria, however in select cases a definitive diagnostic assessment remains challenging and additional diagnostic biomarkers would be advantageous. We analyzed melanomas, nevi, Spitz nevi and atypical spitzoid tumors using parallel sequencing (exons of 611 genes and 507 gene translocation analysis) and methylation arrays (850k Illumina EPIC). By combining detailed genetic and epigenetic analysis with reference-based and reference-free DNA methylome deconvolution we compared Spitz nevi to nevi and melanoma and assessed the potential for these methods in classifying challenging spitzoid tumors. Results were correlated with clinical and histologic features. Spitz nevi were found to cluster independently of nevi and melanoma and demonstrated a different mutation profile. Multiple copy number alterations and TERT promoter mutations were identified only in melanomas. Genome-wide methylation in Spitz nevi was comparable to benign nevi while the Leukocytes UnMethylation for Purity (LUMP) algorithm in Spitz nevi was comparable to melanoma. Histologically difficult to classify Spitz tumor cases were assessed which, based on methylation arrays, clustered between Spitz nevi and melanoma and in terms of genetic profile or copy number variations demonstrated worrisome features suggesting a malignant neoplasm. Comprehensive sequencing and methylation analysis verify Spitz nevi as an independent melanocytic entity distinct from both nevi and melanoma. Combined genetic and methylation assays can offer additional insights in diagnosing difficult to classify Spitzoid tumors.

Melanoma arising in extracutaneous cellular blue nevus: report of two cases with comparison to cutaneous counterparts and uveal melanoma

AIMS

Blue nevi are benign melanocytic lesions that typically occur in the dermis. Melanoma arising in blue nevus is rare and shows a molecular profile distinct from conventional forms of cutaneous melanoma and more similar to uveal melanoma and central nervous system (CNS) melanocytomas. In contrast to conventional cutaneous melanoma, these tumor types typically show activating driver mutations in GNAQ or GNA11, a low mutational burden without evidence of a UV signature, and a reproducible pattern of chromosomal copy number changes. Blue nevi can also occur at extracutaneous sites. Here we report two cases of melanoma arising in extracutaneous blue nevus and compare their molecular features to cohorts of melanoma arising in cutaneous blue nevus (5 patients) and uveal melanoma (6 patients).

METHODS AND RESULTS

We describe the clinical, histomorphologic, immunohistochemical, and molecular findings in these two cases of melanoma arising in extracutaneous blue nevus. We compare their molecular profiles to melanomas arising in cutaneous blue nevus and uveal melanoma using a targeted next-generation DNA sequencing platform and find striking similarities between all three groups.

CONCLUSIONS

The close relationship between blue nevus-associated melanomas, regardless of their anatomic site, supports and validates the concept of melanoma arising in extracutaneous blue nevus and suggests that the two groups share common pathogenic mechanisms. The similarity of both groups to uveal melanoma in turn supports the close relationship between blue nevus-associated melanoma, uveal melanoma, and CNS melanocytoma, and their distinction from conventional UV-associated melanoma. These findings have important implications for prognosis and therapy.

Comprehensive Clinical, Histopathologic, and Molecular Analysis and Long-term Follow-up of Patients With Nodal Blue Nevi

Blue nevi are benign, melanocytic neoplasms that show a range of clinical and morphologic patterns and include common/dendritic, cellular, and atypical cellular subtypes. Like other nevi, they most commonly occur in skin but can occasionally involve lymph nodes where they may be misinterpreted as representing metastatic melanoma. Moreover, whether benign blue nevi can metastasize to lymph nodes and their natural history and prognostic significance has been the subject of great controversy. To date, few cases of nodal blue nevi have been reported in the literature, and those reports have had limited clinical follow-up and supporting molecular data. This study sought to determine the clinical, pathologic, and molecular features of blue nevi involving lymph nodes, clarify their clinical significance, provide evidence for understanding their pathogenesis, and highlight potential pitfalls in the interpretation of lymph nodes with an ultimate aim of improving patient care. Thirteen cases of blue nevi involving lymph nodes were identified in the archives of Royal Prince Alfred Hospital, Sydney, Australia (1984-2018). A detailed assessment of the clinical and pathologic features of each case was performed, including an evaluation of all available immunohistochemical stains. Extended clinical follow-up was available for 9 patients. Droplet digital polymerase chain reaction for GNAQ Q209L, Q209P and GNA11 Q209L mutations was performed on 7 cases of blue nevi within lymph nodes together with matching cutaneous (presumed primary) blue nevi in 2 cases. All cases showed typical histologic features of blue nevi. BAP1 was retained in all cases (n=7). There were no recurrence or metastasis of blue nevus in any case on long-term clinical follow-up (n=9, median follow-up, 12 y). The majority of cases (n=5 of 7 evaluated) had GNAQ and GNA11 driver mutations. The 2 patients with a matched primary cutaneous blue nevus and regionally associated nodal blue nevus had the same GNAQ Q209L mutation in both sites in each patient. We conclude that blue nevi can involve lymph nodes and are associated with benign clinical behavior, and probably represent so-called "benign" metastasis. Awareness of these lesions is important when evaluating lymph nodes to avoid misdiagnosis as metastatic melanoma.

Congenital uveal malignant melanoma- A rare case report

Purpose

To report a rare case of congenital uveal malignant melanoma from Indian subcontinent in an infant with multiple cutaneous naevi and no distant metastasis.

Observation

An 8 month old male child presented with proptosis and black discoloration in the right eye since birth. Enucleation of the right eye was performed and specimen sent for histopathology and immunohistochemical analysis. Results were strongly suggestive of a malignant melanoma of uvea. No metastasis was found on MRI scan of brain, chest and abdomen. Patient is on close follow up and will be subjected to metastasis workup every 6 months.

Conclusion and importance

This entity of congenital uveal malignant melanoma is rather rare with very few reported cases across the globe and needs further understanding of its correct line of treatment.

RASGRF1-rearranged Cutaneous Melanocytic Neoplasms With Spitzoid Cytomorphology: A Clinicopathologic and Genetic Study of 3 Cases

Spitz neoplasms, according to 2018 WHO Blue Book, are morphologically defined by spindled and/or epithelioid melanocytes and genetically by either HRAS mutations or kinase gene fusions. The terminology "spitzoid" refers to lesions with similar morphology but with alternate or undefined genetic anomalies. Herein, we present 3 melanocytic neoplasms with a spitzoid cytomorphology, variable nuclear atypia, and harboring undescribed fusions involving RASGRF1. Two cases presented as unpigmented papules on the heel of a 26-year-old female (case 1) and the forearm of a 13-year-old boy (case 2). They were classified as low-grade melanocytomas (WHO 2018). The third case appeared as a pigmented ulcer on the sole of a 72-year-old female (case 3) that displayed diagnostic features of an invasive melanoma (Breslow thickness 6 mm, Clark level V). A wide skin reexcision identified an epidermotropic metastasis, and sentinel lymph node biopsy displayed multiple subcapsular metastatic deposits. RNA sequencing revealed CD63::RASGRF1, EHBP1::RASGRF1, and ABCC2::RASGRF1 fusions in cases 1 to 3, respectively. They were confirmed by a RASGRF1 break-apart fluorescence in situ hybridization technique. Translocations of RASGRF1, a gene coding a guanine nucleotide exchange factor but not a kinase, have rarely been reported in tumors. While all these cases showed spitzoid cytomorphology, it is too early to tell if they are true Spitz neoplasms as currently defined.

Subungual melanoma with blue naevus-like morphological features: a clinicopathological retrospective analysis of nine cases

Melanocytic lesions in the nail apparatus are often challenging. Both subungual melanomas (SUM) and blue naevus of the nail are very rare. Occasionally, melanomas may mimic blue naevus histologically. Benign and malignant blue melanocytic lesions are commonly associated with G protein mutations, a distinct abnormality not associated with conventional subungual melanomas. We describe the clinical, histological and immunohistochemical features of nine cases of SUM with blue naevus-like morphological features. Mutations in exon 4 and 5 of GNAQ and GNA11 were investigated in two cases, which showed no mutations. RNA-seq of one case revealed unknown mutations along with mutations in ATM, METK and ARID1A. Our study delineates a variant of SUM that mimics blue naevus. Awareness of this pitfall is important when evaluating heavily pigmented lesions around the nail in order to avoid misdiagnosis. Appropriate sampling of subungual lesions and clinicopathological correlation are paramount to reach the correct diagnosis.

Genomic Profiling of Metastatic Uveal Melanoma Shows Frequent Coexisting BAP1 or SF3B1 and GNAQ/GNA11 Mutations and Correlation With Prognosis

OBJECTIVES

To identify therapeutic targets and correlate with clinical outcomes from mutation profiling of metastatic uveal melanoma (UM) using next-generation sequencing (NGS).

METHODS

Melanoma cases that were tested using DNA-based NGS panels of 25 and/or 214 genes were evaluated retrospectively (263 cases) and identified 27 UM cases. BAP1 expression was examined by immunohistochemistry.

RESULTS

Mutations in GNA11 (14) and GNAQ (12) were found in 96% (n = 27) of cases of UM, and most had coexisting BAP1 (17) or SF3B1 (4) mutations. Coexisting GNAQ/11-SF3B1 mutations correlated with a longer average time to first metastasis compared with GNAQ/11-BAP1 mutations (99.7 vs 38.5 months, P = .047). Three patients with BAP1 mutations received trametinib; two are still alive (15 months; 23 months), and one died (32 months). In non-UMs, only 4.2% (n = 236) had BAP1 and 3.8% had SF3B1 mutations; none had coexisting GNAQ/11 mutations.

CONCLUSIONS

Coexisting BAP1/SF3B1 and GNAQ/11 mutations were unique to UM. SF3B1 mutations were reported to be UM-specific in melanoma and associated with rare/no metastasis. The finding of mutated SF3B1 in 14.8% (n = 27) of UMs suggests its role should be further evaluated. The correlation of BAP1/SF3B1 mutation with survival also warrants investigation.

Genomic and Transcriptomic Underpinnings of Melanoma Genesis, Progression, and Metastasis

Melanoma is a deadly skin cancer with rapidly increasing incidence worldwide. The discovery of the genetic drivers of melanomagenesis in the last decade has led the World Health Organization to reclassify melanoma subtypes by their molecular pathways rather than traditional clinical and histopathologic features. Despite this significant advance, the genomic and transcriptomic drivers of metastatic progression are less well characterized. This review describes the known molecular pathways of cutaneous and uveal melanoma progression, highlights recently identified pathways and mediators of metastasis, and touches on the influence of the tumor microenvironment on metastatic progression and treatment resistance. While targeted therapies and immune checkpoint blockade have significantly aided in the treatment of advanced disease, acquired drug resistance remains an unfortunately common problem, and there is still a great need to identify potential prognostic markers and novel therapeutic targets to aid in such cases.

Primary orbital melanoma arising in an atypical diffuse (plaque-like) blue naevus/melanocytosis: a case report and review of literature

Background

Primary orbital melanoma is a rare disease and can occasionally develop from a pre-existing neoplasm of the blue naevus family of melanocytic lesions.

Case presentation

Herein we report a rare case of primary orbital melanoma arising from an unusual atypical diffuse (plaque-like) blue naevus/melanocytosis. A 27 year old man presented with mild pain and swelling of the left eye. Magnetic Resonance Imaging revealed a left lateral episcleral orbital mass and an incisional biopsy confirmed the diagnosis of malignant melanoma. Skin-sparing total left orbital exenteration was performed. Histopathological examination of the exenteration specimen revealed a primary orbital melanoma arising in a pre-existing blue naevus like melanocytosis.

We demonstrate the evidence for histological progression, characterise the molecular profile of this tumour and discuss the related literature.

Conclusions

This case emphasises the importance of a meticulous clinicopathological correlation in recognising such a tumour as a primary orbital melanoma rather than a metastasis, which is managed differently.

Co-occurrence of BAP1 and SF3B1 mutations in uveal melanoma induces cellular senescence

Uveal melanoma (UM) is the most common intraocular tumor in adults. Recurrent mutations in BRCA1‐associated protein 1 (BAP1) and splicing factor 3B subunit 1 (SF3B1) display a mutually exclusive pattern in UM, but the underlying mechanism is unknown. We show that combined BAP1 deficiency and SF3B1 hotspot mutation lead to senescence and growth arrest in human UM cells. Although p53 protein expression is induced, deletion of TP53 (encoding p53) only modestly rescues the observed senescent phenotype. UM cells with BAP1 loss or SF3B1 mutation are more sensitive to chemotherapeutic drugs compared with their isogenic parental cells. Transcriptome analysis shows that DNA‐repair genes are downregulated upon co‐occurrence of BAP1 deletion and SF3B1 mutation, thus leading to impaired DNA damage response and the induction of senescence. The co‐occurrence of these two mutations reduces invasion of UM cells in zebrafish xenograft models and suppresses growth of melanoma xenografts in nude mice. Our findings provide a mechanistic explanation for the mutual exclusivity of BAP1 and SF3B1 mutations in human UM.

Primary Cilia Are Preserved in Cellular Blue and Atypical Blue Nevi and Lost in Blue Nevus-like Melanoma

Distinguishing cellular blue nevi (CBNs) and atypical CBNs from blue nevus-like melanoma (BNLM) can be diagnostically challenging. Immunohistochemistry may inform the diagnosis in a subset of cases but is not always diagnostic. Further, ancillary molecular testing is expensive and often requires significant tissue to complete. Primary cilia are cell-surface organelles with roles in signal transduction pathways and have been shown to be preserved in conventional melanocytic nevi but lost in melanoma. Immunofluorescence staining of primary cilia can be performed using a single standard-thickness formalin-fixed paraffin-embedded tissue section and has a turnaround time similar to immunohistochemistry. The percentage of tumoral melanocytes retaining a primary cilium is quantified and reported as the ciliation index. In the current study, we explored the utility of the ciliation index in a series of 31 blue nevus-like lesions, including CBNs (12), atypical CBNs (15), and BNLM (4). The average ciliation index for the CBNs was 59±18%, with a median of 60 (range: 28 to 87). The average ciliation index for atypical CBNs was 59±23, with a median of 59 (range: 20 to 93). The average ciliation index for BNLM was 4±3, with a median of 3 (range: 1 to 8). There was no significant difference in ciliation index between the CBN and atypical CBN categories. There was a significant difference between CBN and BNLM and between atypical CBNs and BNLM (P<0.001 for each). Here, we show that ciliation index is a quantitative diagnostic tool useful in the setting of blue nevus-like neoplasms, with benefits including cost and time efficiency.

Scientific and clinical implications of genetic and cellular heterogeneity in uveal melanoma

Here, we discuss the presence and roles of heterogeneity in the development of uveal melanoma. Both genetic and cellular heterogeneity are considered, as their presence became undeniable due to single cell approaches that have recently been used in uveal melanoma analysis. However, the presence of precursor clones and immune infiltrate in uveal melanoma have been described as being part of the tumour already decades ago. Since uveal melanoma grow in the corpus vitreous, they present a unique tumour model because every cell present in the tumour tissue is actually part of the tumour and possibly plays a role. For an effective treatment of uveal melanoma metastasis, it should be clear whether precursor clones and normal cells play an active role in progression and metastasis. We propagate analysis of bulk tissue that allows analysis of tumour heterogeneity in a clinical setting.

Melanoma Ex Blue Nevus With GNA11 Mutation and BAP1 Loss: Case Report and Review of the Literature

Cutaneous melanomas may demonstrate a variety of histopathological features and genetic abnormalities. Melanomas that arise in the setting of blue nevi, also known as "malignant blue nevus" or melanoma ex blue nevus (MBN), share a similar histopathological and mutational profile with uveal melanoma. Most uveal melanomas show characteristic GNA11 or GNAQ mutations; additional BAP1 mutation or loss is associated with the highest risk of metastasis and worst prognosis. However, the significance of BAP1 loss in melanomas ex blue nevus remains unclear. We present a case of MBN arising from the scalp of a 21-year-old woman. The diagnosis was established on histopathological findings demonstrating a markedly atypical melanocytic proliferation with increased mitotic activity, necrosis, and a focus of angiolymphatic invasion. Immunohistochemical analysis demonstrated the absence of BAP1 nuclear expression within tumor cells. Next generation sequencing detected GNA11 Q209L mutation and BAP1 loss (chromosome 3p region loss), supporting the diagnosis. We reviewed another 21 MBN cases with reported BAP1 status from the literature. MBN with BAP1 loss presented at a younger average age (41 vs. 61 years), demonstrated larger average lesion thickness (9.0 vs. 7.3 mm), and had a higher rate of metastasis (50% vs. 33%) compared with BAP1-retained MBN. BAP1 expression studies may assist in the diagnosis and management of MBN, but further research is needed.

Uterine Cellular Blue Nevus Arising in Mullerian and Pelvic Dendritic Melanocytosis: Case Report of a Rare Phenomenon to Be Distinguished From Uterine Melanoma

A 37-yr-old woman presented to the gynecology clinic with abnormal uterine bleeding in the setting of known, large uterine fibroids. Preoperative endometrial biopsy identified atypical melanocytic cells concerning for uterine melanoma. Care was transferred to the gynecologic oncology service for hysterectomy. Intraoperative findings included macular, blue-black pigmentation of the peritoneum of the bladder and cervix, which was resected and sent for frozen section, confirming melanocytic neoplasia. The hysterectomy revealed multiple tan leiomyomas up to 12 cm, and a distinct 3 cm black, incompletely circumscribed mass in the endomyometrium composed of bland spindled cells with delicate melanin granules. The tumor cells were positive for Sox-10, BAP1, and Mart-1 (Melan-A) and negative for PRAME, PD-L1, and BRAFV600E by immunostains. Microscopic elements of similar melanocytes and melanophages were found in the cervix and bladder peritoneum. Molecular analysis of the uterine tumor identified a GNA11 mutation but no TERT or BAP1 mutation. The uterine melanocytic tumor has characteristic findings of a cellular blue nevus arising in association with dendritic melanocytosis of Mullerian and pelvic tissues, a rarely seen benign phenomenon that should be distinguished from malignant melanoma of the upper genital tract.

Expanding Our Understanding of Nevogenesis: Copy Number Gain of Chromosome 15q in Melanocytic Nevi Is Associated With Distinct Histomorphologic Findings

As the landscape of melanomagenesis becomes better refined through increasingly detailed schema grounded in distinct clinicopathologic-molecular pathways, the stepwise process and variations of molecular nevogenesis have largely remained elusive. Herein, we present a series of 8 melanocytic nevi in patients ranging from 40 to 74 years of age (median: 59.5 y), which demonstrated a reproducible constellation of histomorphologic features as well as a copy number gain of the long arm of chromosome 15 (15q). The most characteristic histologic feature was sclerosis with maturation at the base of the lesion. All cases demonstrated a dome-shaped configuration and epidermal acanthosis with hyperpigmentation. However, the cytologic features ranged in their appearances from that of a banal nevus with ovoid nuclei, inconspicuous nucleoli, and minimal cytoplasm to enlarged, epithelioid forms with central nucleoli and abundant cytoplasm. No lesions showed staining with BRAF V600E or NRAS Q61R immunohistochemistry. Single-nucleotide polymorphism-based chromosome microarray analysis revealed a monoaberrant 15q gain in all cases. The histology was sufficiently distinctive in the initial 6 cases encountered to allow for prospective identification of 2 additional cases harboring a 15q gain. The clinical follow-up did not reveal recurrence in any case. Although adverse outcomes were not observed in our cohort, future studies are needed to more adequately characterize the clinical and biological behavior of these lesions.

Melanocytic lesions with blue naevus-like (dendritic) morphology: an update with an emphasis on histopathological, immunophenotypic, and molecular features

An accurate diagnosis of melanocytic lesions requires a thorough histopathological evaluation accompanied by appropriate correlation with clinical examination findings. Although most melanocytic lesions can readily be classified as one of the defined diagnostic entities according to well-established diagnostic criteria, a subset of melanocytic lesions, particularly those with blue naevus-like (pigmented dendritic) morphology, have notoriously constituted an enduring challenge for pathologists. These lesions are rare and often show histological ambiguities, with features of both benignity and malignancy, thereby making accurate risk assessment and prediction of their biological behaviours difficult on histological grounds alone. Herein, we outline a practical and systematic approach for the diagnosis of melanocytic lesions with dendritic morphology, with a particular focus on histological and immunophenotypic features that help to distinguish one entity from another. In this review, we provide the most current knowledge on these melanocytic lesions in the literature and our experience with these rare entities, and we discuss the utility of molecular techniques as an ancillary tool, especially in histologically ambiguous and/or borderline lesions.

The genetic and epigenetic basis of distinct melanoma types

Melanoma represents the deadliest skin cancer. Recent therapeutic developments, including targeted and immune therapies have revolutionized clinical management and improved patient outcome. This progress was achieved by rigorous molecular and functional studies followed by robust clinical trials. The identification of key genomic alterations and gene expression profiles have propelled the understanding of distinct characteristics within melanoma subtypes. The aim of this review is to summarize and highlight the main genetic and epigenetic findings of melanomas and highlight their pathological and therapeutic importance.

Molecular pathology as a diagnostic aid in difficult-to-classify melanocytic tumours with spitzoid morphology

Accurate classification of melanocytic proliferations has important implications for prognostic prediction, treatment and follow-up. Although most melanocytic proliferations can be accurately classified using clinical and pathological criteria, classification (specifically distinction between nevus and melanoma) can be challenging in a subset of cases, including those with spitzoid morphology. Genetic studies have shown that mutation profiles differ between primary melanoma subtypes and Spitz nevi. These differences may aid in distinguishing benign from malignant in some melanocytic tumours. Here, we present a selection of melanocytic proliferations with equivocal histopathological criteria, wherein genetic analysis was requested to help guide classification. In two of four cases, the genetic results offered valuable insights, allowing a definitive diagnosis, indicating the diagnostic value of mutation profiling in a real-world routine clinical setting. Although histopathological assessment remains decisive in melanocytic proliferation classification, we recommend including genetic profiling in cases of borderline or atypical lesion to support accurate classification.

Atypical Cellular Blue Nevus With Necrosis Mimicking Melanoma Ex-Blue Nevus

ABSTRACT

Histologic distinction between melanoma ex-blue nevus and cellular blue nevus (CBN) can often be difficult, but features supporting melanoma include infiltrative growth pattern, frequent mitoses, cytologic atypia and pleomorphism, cell crowding, and tumor necrosis. Unfortunately, these features are not constantly dependable and frequently borderline lesions exist, so-called atypical CBN, which lack explicit malignant features. Furthermore, some CBN and atypical CBN show an assortment of features, which may lead to their misdiagnosis as melanoma, but to date necrosis is generally absent. We present an unusual case of an atypical cellular blue nevus with extensive necrosis mimicking melanoma ex-blue nevus.

FBXO32 links ubiquitination to epigenetic reprograming of melanoma cells

Ubiquitination by serving as a major degradation signal of proteins, but also by controlling protein functioning and localization, plays critical roles in most key cellular processes. Here, we show that MITF, the master transcription factor in melanocytes, controls ubiquitination in melanoma cells. We identified FBXO32, a component of the SCF E3 ligase complex as a new MITF target gene. FBXO32 favors melanoma cell migration, proliferation, and tumor development in vivo. Transcriptomic analysis shows that FBXO32 knockdown induces a global change in melanoma gene expression profile. These include the inhibition of CDK6 in agreement with an inhibition of cell proliferation and invasion upon FBXO32 silencing. Furthermore, proteomic analysis identifies SMARC4, a component of the chromatin remodeling complexes BAF/PBAF, as a FBXO32 partner. FBXO32 and SMARCA4 co-localize at loci regulated by FBXO32, such as CDK6 suggesting that FBXO32 controls transcription through the regulation of chromatin remodeling complex activity. FBXO32 and SMARCA4 are the components of a molecular cascade, linking MITF to epigenetics, in melanoma cells.

Genetic drivers of non-cutaneous melanomas: Challenges and opportunities in a heterogeneous landscape

Non-cutaneous melanomas most frequently involve the uveal tract and mucosal membranes, including the conjunctiva. In contrast to cutaneous melanoma, they often present at an advanced clinical stage, are associated with worse clinical outcomes and show poorer responses to immunotherapy. The mutational load within most non-cutaneous melanomas reflects their lower ultraviolet light (UV) exposure. The genetic drivers within non-cutaneous melanomas are heterogeneous. Within ocular melanomas, posterior uveal tract melanomas typically harbour one of two distinct, sets of driver mutations and alterations of clinical and biological significance. In contrast to posterior uveal tract melanomas, anterior uveal tract melanomas of the iris and conjunctival melanomas frequently carry both a higher mutational burden and specific mutations linked with UV exposure. The genetic drivers in iris melanomas more closely resemble those of the posterior uveal tract, whereas conjunctival melanomas harbour similar genetic driver mutations to cutaneous melanomas. Mucosal melanomas occur in sun-shielded sites including sinonasal and oral cavities, nasopharynx, oesophagus, genitalia, anus and rectum, and their mutational landscape is frequently associated with a dominant process of spontaneous deamination and infrequent presence of UV mutation signatures. Genetic drivers of mucosal melanomas are diverse and vary with anatomic location. Further understanding of the causes of already identified recurrent molecular events in non-cutaneous melanomas, identification of additional drivers in specific subtypes, integrative multi-omics analyses and analysis of the tumor immune microenvironment will expand knowledge in this field. Furthermore, such data will likely uncover new therapeutic strategies which will lead to improved clinical outcomes in non-cutaneous melanoma patients.

BAP-1 Expression Status by Immunohistochemistry in Cellular Blue Nevus and Blue Nevus-like Melanoma

The family of blue nevi includes the common blue nevus (BN), cellular blue nevus (CBN), and atypical BN, while melanomas with BN-like morphology can either arise in association with a blue nevus (MABN) or in the de novo setting mimicking cellular blue nevus (MMCBN). Recent molecular and immunohistochemical studies have demonstrated loss of BAP-1 in MABN/MMCBN but not in BN/CBN, suggesting that loss of BAP-1 correlates with a malignant phenotype in these lesions. In this study, we applied anti-BAP-1 antibodies to a series of CBN/BN (n = 11) and MABN/MMCBN (n = 4). Nuclear BAP-1 expression was detected in the majority of CBN/BN (n = 10/11) but was lost in 1 case. Most cases of MABN/MMCBN showed loss of nuclear BAP-1 expression (n = 3/4), with one case of MMCBN showing preserved BAP-1 expression. Demonstration of BAP-1 loss in a single case of CBN and preservation of BAP-1 expression in 1 case of MMCBN may indicate that detection of alterations in BAP-1 protein expression by immunohistochemistry may not be a completely reliable biomarker for the distinction of BN/CBN from MABN/MMCBN. Further investigation of the significance of BAP-1 loss/preservation in BN-like tumors is warranted.

Primary intra-abdominal melanoma arising in association with extracutaneous blue naevus: a report of two cases

AIMS

Blue naevi are uncommon dermal melanocytic neoplasms characterised by GNAQ/GNA11 mutations, which very rarely progress to melanoma. Such melanomas also often have BAP1 mutations, and lack genetic events associated with conventional melanoma. Exceptionally, blue naevi arise in extracutaneous locations; one melanoma arising in this setting has been reported. We report the clinicopathological, immunohistochemical and molecular genetic features of two cases of melanoma arising in extracutaneous blue naevus.

METHODS AND RESULTS

Both arose in males, aged 25 and 63 years, with no history of other melanocytic lesions, and presented as large, painful intra-abdominal masses. The tumours were dark-brown/black, multilobulated, involved small intestinal mesentery and consisted of a predominantly fascicular and spindled, but occasionally nested and epithelioid, proliferation of variably pigmented, relatively monotonous cells with pale cytoplasm and ovoid nuclei with mild to moderate atypia. Mitotic activity was variable but generally low. Both cases showed areas of conventional and cellular blue naevus. Recurrent tumour in one case showed predominantly epithelioid morphology and greater cytological atypia and mitotic activity. One case expressed Melan-A, SOX10 and CD117, with absent expression of S100 protein and DOG1; the other expressed Melan-A, HMB45 and S100 protein. Next-generation sequencing identified GNAQ and BAP1 mutations in one case and GNA11 mutation in the other. Both patients developed widespread metastatic disease.

CONCLUSION

Exceptionally rare, aggressive melanomas arising in extracutaneous blue naevi should be distinguished from metastatic melanoma, gastrointestinal stromal tumour and malignant melanotic nerve sheath tumour, especially given the significant therapeutic and prognostic differences between these different entities.

Genomic and Clinicopathologic Characteristics of PRKAR1A-inactivated Melanomas: Toward Genetic Distinctions of Animal-type Melanoma/Pigment Synthesizing Melanoma

Melanocytic tumors with inactivation of protein kinase A regulatory subunit-α (PRKAR1A) have large oval nuclei and intense pigmentation. Historically, these tumors have been categorized under various names, including epithelioid blue nevus, pigmented epithelioid melanocytoma (PEM) and animal-type melanoma. Although a subset of PEM harbor BRAF activating mutations and biallelic inactivation of PRKAR1A, there are only a few reports of melanomas, or of tumors with genomic alterations beyond those of PEMs. Herein, we describe the clinicopathologic and genetic features of 8 melanomas and tumors that lack PRKAR1α expression by immunohistochemistry but do not fit with conventional PRKAR1A-inactivated melanocytomas. These tumors tended to affect younger patients than conventional melanomas (median age=38 y) and presented as dark brown/black papules and nodules. Histopathologically, they demonstrated nodularity, sometimes in a background of conventional melanoma, and large vesicular nuclei with prominent nucleoli. With the exception of 1 case, the mitotic index was not significantly elevated. Immunohistochemically, all cases showed loss of PRKAR1α and of p16 expression. Seven tumors underwent massively parallel short read (next-generation) sequencing of a panel of 480 cancer-associated genes. Five tumors demonstrated truncating mutations of PRKAR1A and the 2 in which such mutations were not identified demonstrated loss of heterozygosity of the PRKAR1A locus. Four of the tumors harbored BRAF V600E mutations, and 1 harbored a FAM39B-BRAF gene fusion. Another harbored a GNA11 activating mutation. A MAP kinase activating mutation was not identified in the remaining case. Four tumors displayed TERT promoter mutations and chromosomal copy number changes supporting the diagnosis of melanoma. Two cases without these alterations and were classified as "high-grade PRKAR1A-inactivated melanocytomas". The 1 case with widespread metastases demonstrated mutations in TP53 and RB1. Overall, we provide the first genetic characterization of PRKAR1A-inactivated melanomas, discuss the differential diagnosis of heavily pigmented epithelioid melanocytic neoplasms, and propose a new nomenclature for such tumors.

Endothelin signaling promotes melanoma tumorigenesis driven by constitutively active GNAQ

The G-protein-coupled receptor, endothelin receptor B (EDNRB), is an important regulator of melanocyte survival and proliferation. It acts by stimulating downstream heterotrimeric G proteins, such as Gα_q and Gα₁ . Constitutively active, oncogenic versions of Gα_q and Gα₁₁ drive melanomagenesis, but the role of Ednrb in the context of these mutant G proteins has not been previously examined. In this paper, we used a knock-in mouse allele at the Rosa26 locus to force oncogenic GNAQ^Q209L expression in melanocytes in combination with Ednrb gene knockout. The resulting pathological analysis revealed that every aspect of melanomagenesis driven by GNAQ^Q209L was inhibited. We conclude that even in the presence of oncogenic Gα_q , the Ednrb receptor activates normal Gα_q and Gα₁₁ proteins. This likely promotes tumorigenesis by activating phospholipase C-beta, the immediate effector of Gα_q/11 . These findings suggest that it might be possible to target upstream receptors to offset the effects of hyperactive G proteins, recognized as the cause of a growing number of human disorders.

Melanotic Schwannoma of the Vulva: A Case Report and Review of the Literature

Melanotic schwannoma is a pigmented tumor of peripheral nerve differentiation. Primary cutaneous presentations are extremely rare, as the bulk of melanotic schwannomas tend to develop in paraspinal and axial sites. Tumors arise sporadically and in the setting of the Carney complex. Alterations in the gene encoding protein kinase A regulatory subunit-α (PRKAR1A) underlie most patients with the Carney complex and mediate melanotic schwannoma tumorigenesis. Melanotic schwannomas from noncutaneous sites can locally recur and metastasize widely, leading to a recent proposal to change the nomenclature to "malignant melanotic schwannian tumor." However, the clinicopathologic features of primary cutaneous melanotic schwannomas are relatively unexplored. We present a case of a nodule arising on the vulva of a 34-year-old woman. Microscopically, a dermal-based, heavily pigmented proliferation of plump spindled and epithelioid cells arrayed in nodules and fascicles was seen. Lesional cells stained positively for S100, Melan-A, and BAP1 but were negative for Prkar1α. Next-generation sequencing of a panel of 480 cancer-associated genes revealed that the tumor harbored a PRKAR1A p.S299fs truncating mutation and copy neutral loss of heterozygosity of chromosome 17q, the locus at which PRKAR1A resides. Importantly, no other genetic abnormalities or chromosomal copy number changes were identified. On the basis of combined histopathologic, immunohistochemical, and genetic features, a diagnosis of melanotic schwannoma was rendered. Overall, we present the first clinicopathologic description of a vulvar melanotic schwannoma, review the literature concerning cutaneous presentations of melanotic schwannoma, and propose that melanotic schwannian tumors native to skin may behave more indolently than their noncutaneous counterparts.