TERT Promoter Mutations Are Predictive of Aggressive Clinical Behavior in Patients with Spitzoid Melanocytic Neoplasms

Clinical, Morphologic, and Molecular Features of MAP3K8 Rearranged Spitz Neoplasms: A Retrospective Study Documenting That Bonafide Spitz Melanomas Are Rare

Previous studies regarding the clinical behavior of Spitz neoplasms lack genomic characterization. We aim to assess our hypothesis that most MAP3K8 Spitz neoplasms are indolent despite MAP3K8 being the single most common driver of Spitz melanoma. Further, we aim to identify genomic features associated with aggressive behavior and to better characterize the morphology of these cases. We analyzed the outcomes of MAP3K8 Spitz neoplasms. We also performed a meta-analysis of the outcomes of MAP3K8 Spitz from the literature. Morphologic features were compared with other variants of Spitz using a Student t test and χ 2 test. Two of 35 cases resulted in local recurrence and one of these cases had local regional metastasis; all other cases had no evidence of recurrence (mean follow-up time: 33 mo). MAP3K8 Spitz only rarely results in aggressive behavior. Metastatic cases have genomic mutations associated with tumor progression. Morphologically, MAP3K8 Spitz neoplasms frequently showed nodular silhouette, large cell size, epithelioid morphology, and severe nuclear atypia resulting in more frequent diagnosis as Spitz melanoma. Most MAP3K8 Spitz neoplasms have excellent prognoses, apart from rare cases harboring additional genomic abnormalities associated with tumor progression.

Regional lymph node evaluation in pediatric conventional melanoma subtype: a single-center 10-year review

PURPOSE

To assess the prognostic and therapeutic significance of sentinel lymph node biopsy (SLNB) and completion lymph node dissection (CLND) in pediatric conventional melanoma (CM), while evaluating potential predictive factors for outcomes.

METHODS

We conducted a retrospective analysis of medical records spanning 2009-2020, focusing on patients aged 18 or younger with localized cutaneous conventional melanoma.

RESULTS

Among the 33 patients, SLNB detected metastasis in 57.6% of cases, with 52.6% undergoing CLND. Positive SLN patients had higher relapse risk (HR 5.92; 95% CI 1.27-27.7; P = 0.024) but similar overall survival (HR 3.19; 95% CI 0.31-33.1, P = 0.33). No significant differences in disease-free survival (DFS) and OS were found between patients who underwent CLND and those who did not (HR 1.91; 95% CI 0.49-7.43, P = 0.35, and HR 0.52; 95% CI 0.03-8.32, P = 0.64, respectively). Univariate analysis showed age at diagnosis (P = 0.02) correlated with higher recurrence risk, with a 21% hazard increase per additional year of age.

CONCLUSIONS

Positive SLN status and age at diagnosis were associated with worse DFS in CM patients. Our study did not find any prognostic or therapeutic value in CLND for pediatric melanoma. Further multicenter trials are needed to confirm our single-institution experience.

LEVEL OF EVIDENCE

Level IV.

Kinase Fusions in Spitz Melanocytic Tumors: The Past, the Present, and the Future

In recent years, particular interest has developed in molecular biology applied to the field of dermatopathology, with a focus on nevi of the Spitz spectrum. From 2014 onwards, an increasing number of papers have been published to classify, stratify, and correctly frame molecular alterations, including kinase fusions. In this paper, we try to synthesize the knowledge gained in this area so far. In December 2023, we searched Medline and Scopus for case reports and case series, narrative and systematic reviews, meta-analyses, observational studies-either longitudinal or historical, case series, and case reports published in English in the last 15 years using the keywords spitzoid neoplasms, kinase fusions, ALK, ROS1, NTRK (1-2-3), MET, RET, MAP3K8, and RAF1. ALK-rearranged Spitz tumors and ROS-1-rearranged tumors are among the most studied and characterized entities in the literature, in an attempt (although not always successful) to correlate histopathological features with the probable molecular driver alteration. NTRK-, RET-, and MET-rearranged Spitz tumors present another studied and characterized entity, with several rearrangements described but as of yet incomplete information about their prognostic significance. Furthermore, although rarer, rearrangements of serine-threonine kinases such as BRAF, RAF1, and MAP3K8 have also been described, but more cases with more detailed information about possible histopathological alterations, mechanisms of etiopathogenesis, and also prognosis are needed. The knowledge of molecular drivers is of great interest in the field of melanocytic diagnostics, and it is important to consider that in addition to immunohistochemistry, molecular techniques such as FISH, PCR, and/or NGS are essential to confirm and classify the different patterns of mutation. Future studies with large case series and molecular sequencing techniques are needed to allow for a more complete and comprehensive understanding of the role of fusion kinases in the spitzoid tumor family.

Melanocytic Neoplasm With KIT and APC Mutations: A New Subtype of Melanocytoma?

ABSTRACT

We report a very unusual case of melanocytic neoplasm appearing clinically as a 0.5-cm dome-shaped pigmented papule on the chest of a 63-year-old man. Microscopically, it was an asymmetric, entirely dermally based neoplasm characterized by a multinodular, vaguely plexiform architecture composed of moderately pleomorphic spindled melanocytes with ample, dusty pigmented cytoplasm and scattered multinucleated cells. The tumor cells were strongly positive for Melan-A, HMB45, S100, and PRAME, whereas p16 showed diffuse nuclear loss. β-catenin presented a strong and diffuse cytoplasmic staining, while nuclei were negative. Despite an increased cellularity, mitotic count was low (1/mm 2 ). Fluorescence in situ hybridization revealed no copy number alteration in melanoma-related genes ( CDKN2A, MYB, MYC, CCND1 and RREB1 ). DNA and RNA sequencing identified KIT c.2458G>T and APC c.6709C>T mutations. No further genetic alteration was detected including TERT-promoter (TERT-p ) hot-spot mutation. A re-excision was performed. A sentinel lymph node biopsy was negative. Clinical investigations revealed no extracutaneous involvement. The patient is disease-free after a follow-up period of 8 months. Given the peculiar morphologic and molecular findings, we hypothesize the lesion may represent a novel subtype of an intermediate grade melanocytic tumor (melanocytoma).

Spitz Melanocytic Tumors: A Fascinating 75-Year Journey

Over the last 75 years, our understanding of Spitz lesions has undergone substantial evolution. Initially considered a specific type of melanoma, the perception has shifted towards recognizing Spitz lesions as a spectrum comprising Spitz nevi, Spitz melanocytomas, and Spitz melanomas. Spitz lesions are known for posing a significant diagnostic challenge regarding the distinction between benign neoplasms displaying atypical traits and melanomas. A comprehensive understanding of their molecular basis and genomic aberrations has significantly improved precision in classifying and diagnosing these challenging lesions. The primary aim of this review is to encapsulate the current understanding of the molecular pathogenesis and distinct clinicopathologic characteristics defining this intriguing set of tumors.

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.

Diagnostic Algorithm to Subclassify Atypical Spitzoid Tumors in Low and High Risk According to Their Methylation Status

Current diagnostic algorithms are insufficient for the optimal clinical and therapeutic management of cutaneous spitzoid tumors, particularly atypical spitzoid tumors (AST). Therefore, it is crucial to identify new markers that allow for reliable and reproducible diagnostic assessment and can also be used as a predictive tool to anticipate the individual malignant potential of each patient, leading to tailored individual therapy. Using Reduced Representation Bisulfite Sequencing (RRBS), we studied genome-wide methylation profiles of a series of Spitz nevi (SN), spitzoid melanoma (SM), and AST. We established a diagnostic algorithm based on the methylation status of seven cg sites located in TETK4P2 (Tektin 4 Pseudogene 2), MYO1D (Myosin ID), and PMF1-BGLAP (PMF1-BGLAP Readthrough), which allows the distinction between SN and SM but is also capable of subclassifying AST according to their similarity to the methylation levels of Spitz nevi or spitzoid melanoma. Thus, our epigenetic algorithm can predict the risk level of AST and predict its potential clinical outcomes.

Spitz Tumors and Melanoma in the Genomic Age: A Retrospective Look at Ackerman's Conundrum

After 25 years, "Ackerman's conundrum", namely, the distinction of benign from malignant Spitz neoplasms, remains challenging. Genomic studies have shown that most Spitz tumors harbor tyrosine and serine/threonine kinase fusions, including ALK, ROS1, NTRK1, NTRK2, NTRK3, BRAF and MAP3K8, or some mutations, such as HRAS and MAP3K8. These chromosomal abnormalities act as drivers, initiating the oncogenetic process and conferring basic bio-morphological features. Most Spitz tumors show no additional genomic alterations or few ones; others harbor a variable number of mutations, capable of conferring characteristics related to clinical behavior, including CDKN2A deletion and TERT-p mutation. Since the accumulation of mutations is gradual and progressive, tumors appear to form a bio-morphologic spectrum, in which they show a progressive increase of clinical risk and histological atypia. In this context, a binary classification Spitz nevus-melanoma appears as no longer adequate, not corresponding to the real genomic substrate of lesions. A ternary classification Spitz nevus-Spitz melanocytoma-Spitz melanoma is more adherent to the real neoplastic pathway, but some cases with intermediate ambiguous features remain difficult to diagnose. A prognostic stratification of Spitz tumors, based on the morphologic and genomic characteristics, as a complement to the diagnosis, may contribute to better treatment plans for patients.

Pediatric Atypical Melanocytic Proliferations: Single-Site Retrospective Cohort Assessment of Treatment and Long-Term Follow-Up

Atypical and malignant cutaneous tumors are understudied in the pediatric population, with limited data on long-term follow-up. This study examines pediatric (0-18 years) atypical melanocytic proliferations over a twenty-year period (January 2002-December2022) using the EPIC SlicerDicer at our institution. Over a twenty-year period, there were 55 cases of pediatric melanoma (53 patients). The median follow-up time was 8 years, 11 months. A proportion of 96% were treated with wide local excision (WLE), and 47% had a sentinel lymph node biopsy (SLNB) (35% positive rate). There were 101 atypical Spitz tumor cases (85% atypical Spitz tumors, 15% Spitz melanoma), with a median follow-up duration of 9 years. A proportion of 77% were treated with WLE (with one patient dying of metastatic disease). There were 10 cases of atypical melanocytic proliferations not otherwise specified, including 5 pigmented epithelioid melanocytomas (PEM), 4 deep-penetrating nevi, and 1 atypical cellular blue nevus. This study adds to the growing body of knowledge on pediatric atypical cutaneous melanocytic proliferations, aligning with many described characteristics such as disease location and overall survival rates, with distinct exceptions (higher melanoma positive SLNB rate, lower atypical Spitz tumor WLE rate, and a case of fatal metastatic atypical Spitz tumor).

Spitz tumor with RAF1 fusion: A report of 3 cases

Spitz tumors are melanocytic neoplasms morphologically characterized by spindled and/or epithelioid cells and specific stromal and epidermal changes associated with mutually exclusive fusion kinases involving ALK, ROS1, NTRK1, NTRK2, NTRK3, MET and RET, BRAF and MAP3K8 genes or, less commonly, HRAS mutation. RAF1 fusions have been recently detected in cutaneous melanocytic neoplasms, including conventional melanoma, congenital nevus and BAP-1 inactivated tumors. We report herewith three Spitz neoplasms with a RAF1 fusion, including a previously reported CTDSPL::RAF1 fusion and two novel PPAP2B::RAF1 and ATP2B4::RAF1 fusions. Two cases were classified as Spitz nevus, while the remaining neoplasm was classified as Spitz melanoma at the time of the diagnosis, given 9p21 homozygous deletion and positive sentinel lymph node biopsy. We suggest that RAF1 fused melanocytic neoplasms can represent a novel subgroup of Spitz tumors, with a RAF1 fusion representing an oncogenic driver.

Novel gene fusion discovery in Spitz tumours and its relevance in diagnostics

In addition to morphologic analysis, molecular diagnostic work up of Spitz tumours is often of great value for their accurate diagnosis/classification. Nowadays, next-generation sequencing (NGS) is the predominant screening method in molecular diagnostics. Up to 80% of these melanocytic neoplasms comprise gene fusions as genetic anomalies for which the driver codes for a protein harbouring a kinase domain. However, because of the variety of fusion partners the use of PCR-based targeted enrichment NGS methods is not recommended. We describe a series of four Spitz tumour samples in which distinct gene fusions were detected by hybridisation-based capture NGS (TPM3::ALK, LIMA1::ROS1, LRRFIP2::ROS1 and MYO5A::RET). Two of these fusions are not previously described. All 4 fusions were confirmed by reverse transcription-PCR. These findings demonstrate the need for molecular analysis that can detect unknown fusions in Spitz neoplasms for optimal diagnosis.

Children's Oncology Group's 2023 blueprint for research: Rare tumors

The Children's Oncology Group (COG) Rare Tumor Committee includes the Infrequent Tumor and Retinoblastoma subcommittees, encompassing a wide range of extracranial solid tumors that do not fall within another COG disease committee. Current therapeutic trial development focuses on nasopharyngeal carcinoma, adrenocortical carcinoma, pleuropulmonary blastoma, colorectal carcinoma, melanoma, and thyroid carcinoma. Given the rarity of these tumors, novel strategies and international collaborative efforts are necessary to advance research and improve outcomes.

TERT Promoter Mutational Analysis as an Ancillary Diagnostic Tool for Diagnostically Challenging Melanocytic Neoplasms

ABSTRACT

Telomerase reverse transcriptase promoter mutations (TPMs) have been shown to be common in melanoma and uncommon in benign nevi. To assess the use of TPMs as an ancillary diagnostic tool, we report the concordance of the TPM status with the final diagnosis in clinical cases with distinct differential diagnostic scenarios: dysplastic nevus versus melanoma, atypical Spitz nevus versus melanoma, atypical deep penetrating nevus (DPN) versus melanoma, and atypical blue nevus versus malignant blue nevus. In a control cohort, we found a positive TPM in 51/70 (73%) of the total melanomas with the highest frequency in vertical growth phase melanoma cases. Conversely, only 2/35 (6%) dysplastic nevi in our control cases were TPM-positive and b were severely atypical dysplastic nevi. Our clinical cohort of 257 cases had a positive TPM in 24% of cases diagnosed as melanoma and in 1% of cases with a benign diagnosis. The overall concordance of the TPM status with the final diagnosis was 86%. The TPM status had the greatest concordance (95%) with the final diagnosis in the atypical DPN versus melanoma group, with the rest of the groups ranging between 50% and 88%. Overall, our results suggest that TPMs are most useful in the differential diagnosis of atypical DPN versus melanoma. It also has some value in the differential diagnosis of atypical Spitz tumor versus melanoma and dysplastic nevus versus melanoma, whereas in our cohort, it did not contribute meaningfully to differentiating malignant blue nevus and atypical blue nevus.

BAP1-Inactivated Melanoma Arising From BAP1-Inactivated Melanocytic Tumor in a Patient With BAP1 Germline Mutation: A Case Report and Review of the Literature

ABSTRACT

BAP1-inactivated melanocytic tumors represent a subset of epithelioid melanocytic neoplasms resulting from biallelic inactivation of the BAP1 gene and by a driver mutation that activate the MAP kinase pathway, most commonly BRAFV600E. They occur sporadically or, less common, in the setting of BAP1 tumor predisposition syndrome caused by a BAP1 germline mutation that predisposes to several malignancies including cutaneous and uveal melanoma. To date, only few cases of BAP1-inactivated melanomas have been reported. We present a case of a 35-year-old woman presented with a melanocytic lesion microscopically composed of 3 distinct melanocytic populations, suggesting a stepwise progression model to melanoma from a conventional nevus through a melanocytoma stage. This progression was also supported from a molecular viewpoint given BRAFV600E, BAP1, and TERT-p hot spot mutations detected by targeted mutational analysis. Four atypical melanocytic lesions were removed from the patient's back, and the same A BAP1 c.856A>T, p.(Lys286Ter) mutation was detected on either tumoral or normal tissue samples. To the best of our knowledge, this is the first case of BAP1-inactivated melanoma with a documented TERT-p hot spot mutation manifesting as the first presentation of BAP1 tumor predisposition syndrome.

Revision of the Melanocytic Pathology Assessment Tool and Hierarchy for Diagnosis Classification Schema for Melanocytic Lesions: A Consensus Statement

IMPORTANCE

A standardized pathology classification system for melanocytic lesions is needed to aid both pathologists and clinicians in cataloging currently existing diverse terminologies and in the diagnosis and treatment of patients. The Melanocytic Pathology Assessment Tool and Hierarchy for Diagnosis (MPATH-Dx) has been developed for this purpose.

OBJECTIVE

To revise the MPATH-Dx version 1.0 classification tool, using feedback from dermatopathologists participating in the National Institutes of Health-funded Reducing Errors in Melanocytic Interpretations (REMI) Study and from members of the International Melanoma Pathology Study Group (IMPSG).

EVIDENCE REVIEW

Practicing dermatopathologists recruited from 40 US states participated in the 2-year REMI study and provided feedback on the MPATH-Dx version 1.0 tool. Independently, member dermatopathologists participating in an IMPSG workshop dedicated to the MPATH-Dx schema provided additional input for refining the MPATH-Dx tool. A reference panel of 3 dermatopathologists, the original authors of the MPATH-Dx version 1.0 tool, integrated all feedback into an updated and refined MPATH-Dx version 2.0.

FINDINGS

The new MPATH-Dx version 2.0 schema simplifies the original 5-class hierarchy into 4 classes to improve diagnostic concordance and to provide more explicit guidance in the treatment of patients. This new version also has clearly defined histopathological criteria for classification of classes I and II lesions; has specific provisions for the most frequently encountered low-cumulative sun damage pathway of melanoma progression, as well as other, less common World Health Organization pathways to melanoma; provides guidance for classifying intermediate class II tumors vs melanoma; and recognizes a subset of pT1a melanomas with very low risk and possible eventual reclassification as neoplasms lacking criteria for melanoma.

CONCLUSIONS AND RELEVANCE

The implementation of the newly revised MPATH-Dx version 2.0 schema into clinical practice is anticipated to provide a robust tool and adjunct for standardized diagnostic reporting of melanocytic lesions and management of patients to the benefit of both health care practitioners and patients.

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.

Fatal melanoma with a novel MYO5A-BRAF fusion and small associated conventional nevus: A case report and review of literature

Kinase fusions play an important role in the pathogenesis of Spitz neoplasms and occasionally non-Spitz neoplasms. We report a case of a 19-year-old woman with a growing nodule on the scalp, morphologically consistent with a diagnosis of melanoma with epithelioid features arising in association with small nevus. This tumor aggressively metastasized and failed to respond to immunotherapy. Next-generation sequencing of a metastatic focus revealed an MYO5A-BRAF kinase fusion with a low mutational burden and fluorescence in situ hybridization (FISH) of the primary melanoma showed similar results. FISH testing of the associated nevus failed because of technical reasons. MYO5A has rarely been reported as the fusion partner with BRAF-rearranged melanocytic tumors. Moreover, this case raises speculations and contributes to the growing literature on the pathogenesis, nomenclature, and tumorigenic pathways in kinase-fusion melanomas. The patient succumbed to disease, which is in concordance with some literature suggesting aggressive behavior of BRAF fusion melanomas with TERT promoter mutations.

Modeling Spitz melanoma in zebrafish using sequential mutagenesis

Spitz neoplasms are a diverse group of molecularly and histologically defined melanocytic tumors with varying biologic potentials. The precise classification of Spitz neoplasms can be challenging. Recent studies have revealed recurrent fusions involving multiple kinases in a large proportion of Spitz tumors. In this study, we generated a transgenic zebrafish model of Spitz melanoma using a previously identified ZCCHC8-ROS1 fusion gene. Animals developed grossly apparent melanocytic proliferations as early as 3 weeks of age and overt melanoma as early as 5 weeks. By 7 weeks, ZCCHC8-ROS1 induced a histologic spectrum of neoplasms ranging from hyperpigmented patches to melanoma. Given the swift onset of these tumors during development, we extended this approach into adult fish using a recently described electroporation technique. Tissue-specific expression of ZCCHC8-ROS1 in adults led to melanocyte expansion without overt progression to melanoma. Subsequent electroporation with tissue-specific CRISPR, targeting only tp53 was sufficient to induce transformation to melanoma. Our model exhibits the use of sequential mutagenesis in the adult zebrafish, and demonstrates that ZCCHC8-ROS1 induces a spectrum of melanocytic lesions that closely mimics human Spitz neoplasms.

Summary: We describe the first animal model of Spitz neoplasms and demonstrate its use for modeling sequential mutagenesis and its potential for studying melanocyte development in vivo.

TERT Promoter Mutations and Telomerase in Melanoma

Malignant melanoma is an extremely malignant tumor with a high mortality rate and an increasing incidence with a high mutation load. The frequency of mutations in the TERT promoter exceeds the frequency of any known noncoding mutations in melanoma. A growing number of recent studies suggest that the most common mutations in the TERT promoter (ATG start site −124C>T and −146C>T) are associated with increased TERT mRNA expression, telomerase activity, telomere length, and poor prognosis. Recently, it has been shown that TERT promoter mutations are more correlated with the occurrence, development, invasion, and metastasis of melanoma, as well as emerging approaches such as the therapeutic potential of chemical inhibition of TERT promoter mutations, direct telomerase inhibitors, combined targeted therapy, and immunotherapies. In this review, we describe the latest advances in the role of TERT promoter mutations and telomerase in promoting the occurrence, development, and poor prognosis of melanoma and discuss the clinical significance of the TERT promoter and telomerase in the treatment of melanoma.

The Spectrum of Spitz Melanocytic Lesions: From Morphologic Diagnosis to Molecular Classification

Spitz tumors represent a distinct subtype of melanocytic lesions with characteristic histopathologic features, some of which are overlapping with melanoma. More common in the pediatric and younger population, they can be clinically suspected by recognizing specific patterns on dermatoscopic examination, and several subtypes have been described. We now classify these lesions into benign Spitz nevi, intermediate lesions identified as “atypical Spitz tumors” (or Spitz melanocytoma) and malignant Spitz melanoma. More recently a large body of work has uncovered the molecular underpinning of Spitz tumors, including mutations in the HRAS gene and several gene fusions involving several protein kinases. Here we present an overarching view of our current knowledge and understanding of Spitz tumors, detailing clinical, histopathological and molecular features characteristic of these lesions.

Emerging mechanisms of telomerase reactivation in cancer

Mutations in the promoter of human telomerase reverse transcriptase (hTERT) result in hyperactivation of hTERT. Notably, all mutations are G>A transitions, frequently found in a wide range of cancer types, and causally associated with cancer progression. Initially, the mutations were understood to reactivate hTERT by generating novel E26 transformation-specific (ETS) binding sites. Recent work reveals the role of DNA secondary structure G-quadruplexes, telomere binding factor(s), and chromatin looping in hTERT regulation. Here, we discuss these emerging findings in relation to the clinically significant promoter mutations to provide a broader understanding of the context-dependent outcomes that result in hTERT activation in normal and pathogenic conditions.

Novel insights into the BAP1-inactivated melanocytic tumor

BAP1-inactivated melanocytic tumor (BIMT) is a group of melanocytic neoplasms with epithelioid cell morphology molecularly characterized by the loss of function of BAP1, a tumor suppressor gene located on chromosome 3p21, and a mutually exclusive mitogenic driver mutation, more commonly BRAF. BIMTs can occur as a sporadic lesion or, less commonly, in the setting of an autosomal dominant cancer susceptibility syndrome caused by a BAP1 germline inactivating mutation. Owing to the frequent identification of remnants of a conventional nevus, BIMTs are currently classified within the group of combined melanocytic nevi. "Pure" lesions can also be observed. We studied 50 BIMTs from 36 patients. Most lesions were composed of epithelioid melanocytes of varying size and shapes, resulting extreme cytomorphological heterogeneity. Several distinctive morphological variants of multinucleated/giant cells were identified. Some hitherto underrecognized microscopic features, especially regarding nuclear characteristics included nuclear blebbing, nuclear budding, micronuclei, shadow nuclei, peculiar cytoplasmic projections (ant-bear cells) often containing micronuclei and cell-in-cell structures (entosis). In addition, there were mixed nests of conventional and BAP1-inactivated melanocytes and squeezed remnants of the original nevus. Of the 26 lesions studied, 24 yielded a BRAF mutation, while in the remaining two cases there was a RAF1 fusion. BAP1 biallelic and singe allele mutations were found in 4/22 and 16/24 neoplasms, respectively. In five patients, there was a BAP1 germline mutation. Six novel, previously unreported BAP1 mutations have been identified. BAP1 heterozygous loss was detected in 11/22 lesions. Fluorescence in situ hybridization for copy number changes revealed a related amplification of both RREB1 and MYC genes in one tumor, whereas the remaining 20 lesions studied were negative; no TERT-p mutation was found in 14 studied neoplasms. Tetraploidy was identified in 5/21 BIMTs. Of the 21 patients with available follow-up, only one child had a locoregional lymph node metastasis. Our results support a progression of BIMTs from a conventional BRAF mutated in which the original nevus is gradually replaced by epithelioid BAP1-inactivated melanocytes. Some features suggest more complex underlying pathophysiological events that need to be elucidated.

Genomic comparison of malignant melanoma and atypical Spitz tumor in the pediatric population

BACKGROUND/OBJECTIVES

The diagnostic distinction between atypical Spitz tumor (AST) and malignant melanoma (MM) in pediatric tumors is challenging. Molecular tests are increasingly used to characterize these neoplasms; however, limited studies are available in pediatric patients. This study aimed to provide a genomic comparison of pediatric MM and AST in the context of comprehensive clinical annotation.

METHODS

Pediatric patients diagnosed with MM (n=11) and AST (n=12) were compared to a cohort of 693 adult melanoma patients. DNA next-generation sequencing assessed kinase gene fusions, tumor mutational burden, sequence variants, copy number alterations, structural variants, microsatellite instability, and mutational signatures.

RESULTS

Seven AST cases and eight MM cases were successfully sequenced. Kinase gene fusions were identified in both the MM and AST cohorts (NTRK1, ROS1, and MET). MM cases had TERT, BRAF, and CDKN2A alterations, which were not identified in the AST cohort. Tumor mutational burden (TMB) analysis showed pediatric ASTs had an average of 2.82 mutations/Mb, pediatric MM had an average of 5.7 mutations/Mb, and adult MM cases averaged 18.8 mut/Mb. One pediatric MM case had an elevated TMB of 15 mutations/Mb and a UV mutational signature.

CONCLUSIONS

These data expand our understanding of pediatric malignant melanoma. The differences between the molecular signatures for AST and MM are not statistically significant, and histopathology remains the gold standard for the diagnosis of pediatric AST and MM at this time. With more data, molecular studies may provide additional support for diagnosis and targeted therapeutics.

The Morpho-Molecular Landscape of Spitz Neoplasms

Spitz neoplasms are a heterogeneous group of melanocytic proliferations with a great variability in the histological characteristics and in the biological behavior. Thanks to recent discoveries, the morpho-molecular landscape of Spitz lineage is becoming clearer, with the identification of subtypes with recurrent features thus providing the basis for a more solid and precise tumor classification. Indeed, specific mutually exclusive driver molecular events, namely HRAS or MAP2K1 mutations, copy number gains of 11p, and fusions involving ALK, ROS, NTRK1, NTRK2, NTRK3, MET, RET, MAP3K8, and BRAF genes, correlate with distinctive histological features. The accumulation of further molecular aberrations, instead, promotes the increasing malignant transformation of Spitz neoplasms. Thus, the detection of a driver genetic alteration can be achieved using the appropriate diagnostic tests chosen according to the histological characteristics of the lesion. This allows the recognition of subtypes with aggressive behavior requiring further molecular investigations. This review provides an update on the morpho-molecular correlations in Spitz neoplasms.

Risk factors for the development of Spitz neoplasms

BACKGROUND/OBJECTIVES

The principal environmental risk factor for conventional nevi and melanomas is ultraviolet exposure. However, little is known about genetic or environmental risk factors for developing Spitz tumors. This study investigates risk factors associated with Spitz neoplasms.

METHODS

Patients with Spitz tumors seen at Northwestern Memorial Hospital and Lurie Children's Hospital were surveyed with a 16-item questionnaire about environmental and inherited factors. Spitz tumor patients were compared to a pediatric control cohort from a similar clinical setting. This was supplemented with a meta-analysis of genetic and environmental causes of Spitz neoplasms.

RESULTS

One hundred and six Spitz and 58 control surveys were obtained and no statistically significant differences in genetic or environmental risk factors were found between Spitz and control groups.

CONCLUSION

Our data and meta-analysis suggest that typical risk factors associated with melanoma are not significantly associated with Spitz tumors. Identification of relevant genetic or environmental risk factors will likely require larger and population-based studies.

Diagnostic and prognostic classification of atypical spitzoid tumours based on histology and genomic aberrations: A prospective cohort study with long-term follow-up

BACKGROUND

Histological classification of atypical spitzoid tumours (ASTs) is unreliable, and categorisation of these lesions into benign and malignant is poorly reproducible. Here, we classified ASTs based on histology and chromosomal aberrations and explored the prognostic significance of genomic aberrations in a prospective cohort with a long-term follow-up.

PATIENTS AND METHODS

Histologically equivocal ASTs from 76 patients were analysed by array comparative genomic hybridisation (aCGH). Tumours were histologically assessed by a panel of dermatopathologist before and after aCGH and classified as benign, ambiguous or malignant. Chromosomal aberrations were correlated with an outcome.

RESULTS

Chromosomal aberrations were detected in 45 (59%) of 76 ASTs (median age: 16 years, range: 0-74; median follow-up: 90 months, range: 13-153). The initial histological diagnosis was changed upon presentation of aCGH results in 36 of 76 cases (47%). The final diagnostic interpretation classified 61% of the lesions as benign, 18% as ambiguous and 21% as malignant. Positive sentinel lymph node biopsies (6+/29) occurred at similar rates in all diagnostic groups (P = 0.83) and were not associated with an unfavourable outcome. Two patients had local recurrences, but none of the patients developed metastasis beyond the sentinel lymph node.

CONCLUSIONS

All ASTs had an excellent prognosis, even in cases with worrisome morphology and chromosomal aberrations. With no distant metastasis or death in long-term follow-up of 76 patients, no correlation between chromosomal aberrations and prognosis was possible. However, it seems likely that in larger cohorts, metastases would arise in cases with complex aberrations and these patients should undergo clinical follow-up.

TERT promoter mutations are associated with longer progression-free and overall survival in patients with BRAF-mutant melanoma receiving BRAF and MEK inhibitor therapy

BACKGROUND

Around 50% of cutaneous melanomas harbour therapeutically targetable BRAF V600 mutations. Reliable clinical biomarkers predicting duration of response to BRAF-targeted therapies are still lacking. Recent in vitro studies demonstrated that BRAF-MEK inhibitor therapy response is associated with tumour TERT promoter mutation status. We assessed this potential association in a clinical setting.

METHODS

The study cohort comprised 232 patients with metastatic or unresectable BRAF V600-mutated melanoma receiving combined BRAF/MEK inhibitor treatment, including a single-centre retrospective discovery cohort (N = 120) and a prospectively collected multicenter validation cohort (N = 112). Patients were excluded if they received BRAF or MEK inhibitors in an adjuvant setting, as monotherapy, or in combination with immunotherapy. Kaplan-Meier and univariate/multivariate Cox regression analyses were performed as appropriate.

RESULTS

median age at first diagnosis was 54 years (range 16-84 years). The majority of patients were men 147/232 (63.4%). Most tumours harboured TERT promoter mutations (72%, N = 167). A survival advantage was observed in both progression-free survival (PFS) and overall survival (OS) for patients with TERT promoter-mutant versus wild-type tumours in both the discovery cohort (mPFS of 9.6 months [N = 87] vs 5.0 months [N = 33]; hazard ratio [HR] = 0.56 [95% confidence interval {CI} 0.33-0.96] and mOS of 33.6 months vs 15.0 months; HR = 0.47 [95%CI 0.32-0.70]) as well as the validation cohort (mPFS of 7.3 months [N = 80] vs 5.8 months [N = 32]; HR = 0.67 [95%CI 0.41-1.10] and mOS of 51.1 months vs 15.0 months; HR = 0.33 [95%CI 0.18-0.63]). In the pooled cohort of TERT promoter-mutant (N = 167) versus wild-type (N = 65) tumours, respectively, PFS was 8.9 versus 5.5 months, (HR = 0.62; 95%CI 0.45-0.87; P = 0.004), and OS was 33.6 versus 17.0 months, (HR = 0.51; 95%CI 0.35-0.75, P = 0.0001).

CONCLUSIONS

In patients with melanoma receiving BRAF/MEK-targeted therapies, TERT promoter mutations are associated with longer survival. If validated in larger studies, TERT promoter mutation status should be included as a predictive biomarker in treatment algorithms for advanced melanoma.

Impact of Next-generation Sequencing on Interobserver Agreement and Diagnosis of Spitzoid Neoplasms

Atypical Spitzoid melanocytic tumors are diagnostically challenging. Many studies have suggested various genomic markers to improve classification and prognostication. We aimed to assess whether next-generation sequencing studies using the Tempus xO assay assessing mutations in 1711 cancer-related genes and performing whole transcriptome mRNA sequencing for structural alterations could improve diagnostic agreement and accuracy in assessing neoplasms with Spitzoid histologic features. Twenty expert pathologists were asked to review 70 consultation level cases with Spitzoid features, once with limited clinical information and again with additional genomic information. There was an improvement in overall agreement with additional genomic information. Most significantly, there was increase in agreement of the diagnosis of conventional melanoma from moderate (κ=0.470, SE=0.0105) to substantial (κ=0.645, SE=0.0143) as measured by an average Cohen κ. Clinical follow-up was available in all 70 cases which substantiated that the improved agreement was clinically significant. Among 3 patients with distant metastatic disease, there was a highly significant increase in diagnostic recognition of the cases as conventional melanoma with genomics (P<0.005). In one case, none of 20 pathologists recognized a tumor with BRAF and TERT promoter mutations associated with fatal outcome as a conventional melanoma when only limited clinical information was provided, whereas 60% of pathologists correctly diagnosed this case when genomic information was also available. There was also a significant improvement in agreement of which lesions should be classified in the Spitz category/WHO Pathway from an average Cohen κ of 0.360 (SE=0.00921) to 0.607 (SE=0.0232) with genomics.

Spitz Melanoma of Childhood With A Novel Promoter Hijacking Anaplastic Lymphoma Kinase (C2orf42-ALK) Rearrangement

ABSTRACT

We present the case of a prepubescent man of African descent who developed a spitzoid melanocytic proliferation showing evidence of a novel promoter hijacking ALK-C2orf42 rearrangement, with atypical histology, clinically apparent metastatic disease, and abnormal cytogenetic findings, representing a rare genuine case of "Spitz melanoma of childhood." As our understanding of the distinct molecular biology of different tumors traditionally grouped as spitzoid melanocytic lesions evolves, it is becoming increasingly apparent that this group encompasses morphologically and genetically distinct entities. Accurate classification with detailed molecular analysis and prolonged clinical follow-up is essential to allow meaningful conclusions regarding prognostication and prediction of response to therapy.

Pigmented Lesions in Children: Update on Clinical, Histopathologic and Ancillary Testing

Patients are commonly referred to pediatric dermatology for the evaluation of pigmented lesions. For families, pediatricians, and dermatologists alike, malignancy is the main fear. In the past few decades, there has been evolving literature to inform diagnosis and management. This article provides an update on the clinical, histopathologic, and ancillary testing for 3 categories of particularly challenging pigmented lesions: congenital melanocytic nevi, spitzoid neoplasms, and pediatric melanoma.

Cutaneous Melanomas Arising during Childhood: An Overview of the Main Entities

Cutaneous melanomas are exceptional in children and represent a variety of clinical situations, each with a different prognosis. In congenital nevi, the risk of transformation is correlated with the size of the nevus. The most frequent type is lateral transformation, extremely rare before puberty, reminiscent of a superficial spreading melanoma (SSM) ex-nevus. Deep nodular transformation is much rarer, can occur before puberty, and must be distinguished from benign proliferative nodules. Superficial spreading melanoma can also arise within small nevi, which were not visible at birth, usually after puberty, and can reveal a cancer predisposition syndrome (CDKN2A or CDK4 germline mutations). Prognosis is correlated with classical histoprognostic features (mainly Breslow thickness). Spitz tumors are frequent in adolescents and encompass benign (Spitz nevus), intermediate (atypical Spitz tumor), and malignant forms (malignant Spitz tumor). The whole spectrum is characterized by specific morphology with spindled and epithelioid cells, genetic features, and an overall favorable outcome even if a regional lymph node is involved. Nevoid melanomas are rare and difficult to diagnose clinically and histologically. They can arise in late adolescence. Their prognosis is currently not very well ascertained. A small group of melanomas remains unclassified after histological and molecular assessment.

A prospective, comprehensive registry that integrates the molecular analysis of pediatric and adolescent melanocytic lesions

BACKGROUND

Childhood melanocytic tumors represent a diagnostic and therapeutic challenge, and additional research is needed to better define the natural history of these tumors.

METHODS

The authors developed a comprehensive, prospective registry called Molecular Analysis of Childhood Melanocytic Tumors for children and adolescents with an atypical Spitz tumor/Spitz melanoma (AST/SM), conventional or adult-type melanoma (CM), melanoma arising in a giant congenital nevus (MCM), or atypical melanocytic proliferation of other types (OT) to better define the clinical behavior of these lesions by incorporating an integrated clinicopathologic and molecular analysis using centralized pathology review and various platforms, including fluorescence in situ hybridization; array comparative genomic hybridization; and whole genome, exome, and capture targeted panels.

RESULTS

From May 2016 to November 2019, 70 children were enrolled with a median age at diagnosis of 9.1 years. Thirty-seven had AST/SM, 17 had CM, 4 had MCM, and 12 had OT. Patients with AST/SM were younger (median age, 7 years), and their tumor most commonly arose in the extremities and trunk. The most common gene rearrangements included MAP3K8 and ALK. None of the 33 patients who underwent a TERT promoter mutation analysis had a mutation, and all patients were alive. Among the CM patients, the median age was 13 years; 11 had a BRAFV600E mutation, and 7 had a TERT promoter mutation. Three patients died of their disease. All 4 patients with MCM harbored an NRASQ61 mutation and died of their disease. The OT group was heterogenous, and all patients survived.

CONCLUSIONS

The incorporation of an integrated clinicopathologic and genomic analysis identifies distinct subgroups of pediatric melanocytic lesions that have different clinical behaviors. The integration of this combined diagnostic modality can help to individualize diagnoses and treatments for these patients.

Combination Therapy With Anti-PD-1 or PD-1 Antibody Alone in Asian Pediatric Patients With Relapsed or Refractory Cancer

There is limited experience of PD-1 antibody combined with other therapies in children. We aimed to explore the antitumor activity and safety of PD-1 antibody monotherapy or combination with other regimens in relapsed or refractory pediatric cancer. This is a retrospective-case study conducted in two Chinese expert centers. The primary objective of this study was to describe the overall response rate (ORR) and disease control rate (DCR). Secondary objectives included characterizing toxicities. Of the 22 pediatric patients with cancer who received PD-1 inhibitors, the median follow-up for all patients after the commencement of PD-1 therapy with or without other regimens was 12.3 months (0 - 43 months). PD-1 antibody monotherapy demonstrated antitumor activity in a population of pediatric patients with Hodgkin lymphoma (HL), with an objective response rate (ORR) and disease control rate (DCR) of 83.3% (3CR and 2PR) and 100%, respectively. However, no objective response was observed in patients with melanoma or Burkitt lymphoma evaluated in this study. We reviewed responses for patients with chemotherapy, decitabine or everolimus combination therapies with PD-1 antibodies, and found that PD-1 antibody combined with decitabine showed potential efficacy in pediatric patients with advanced embryonal rhabdomyosarcoma and lymphoepitheliomatoid-like carcinoma. There were no severe treatment-related adverse events (TRAEs) directly attributed to PD-1 antibody monotherapy in Asian pediatric patients with lower incidence of hematologic toxicity and nonhematologic toxicity. The Grade ≥3 TRAEs were attributed to the combination chemotherapy.

Cutaneous melanoma in children and adolescents: The EXPeRT/PARTNER diagnostic and therapeutic recommendations

Cutaneous melanoma is rare in children and, like other very rare pediatric tumors, it suffers from a shortage of knowledge and clinical expertise. The clinical management of pediatric melanoma is often challenging. Its clinical and pathological diagnosis may be difficult, and there is no standard treatment. In the absence of specific treatment guidelines, young patients are generally treated following the same principle as for adults, but concern remains about their access to clinical trials and new drugs, which have been shown to dramatically change the natural history of advanced melanoma. This paper presents the internationally recognized recommendations for the diagnosis and treatment of children and adolescents with cutaneous melanoma, established by the European Cooperative Study Group for Pediatric Rare Tumors (EXPeRT) within the EU-funded project called PARTNER (Paediatric Rare Tumours Network - European Registry). Main recommendations for melanoma are to discuss pediatric patients in multidisciplinary teams that include both pediatric oncologists and specialists in adult melanoma; to enroll patients in prospective trials, if available; to collect data in national-international databases; and to develop an effective international collaboration between pediatric and adult melanoma groups in order to facilitate the transfer of potentially effective new agents from the adult to the pediatric setting.

Melanoma pathology: new approaches and classification

Cancer is caused by the accumulation of pathogenic alterations of the genome and epigenome that result in permanent changes that disrupt cellular homeostasis. The genes that become corrupted in this process vary among different tumour types, reflecting specific vulnerabilities and dependencies of the cell from which the cancer originated. This also applies to 'melanoma', a cancer that constitutes not one, but multiple diseases that can be separated based on their cell of origin, aetiology, clinical appearance and course, and response to treatment. In this article, we review the current classification of melanoma within distinct evolutionary pathways and the associated genetic alterations. In addition, we review the application of molecular diagnostics to the diagnosis of melanocytic tumours in the context of histopathological assessment.

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.

TERT promoter mutations in penile squamous cell carcinoma: high frequency in non-HPV-related type and association with favorable clinicopathologic features

Purpose

Penile carcinoma is a rare malignant neoplasm with a largely unknown molecular pathogenesis. Telomerase reverse transcriptase promoter (TERT-p) mutations have been detected in several types of human malignancies. The aim of this study was to investigate the presence of TERT-p mutations in penile squamous cell carcinomas (SCCs) and their associations with clinicopathologic features.

Methods

In this retrospective study, Sanger sequencing was performed to detect TERT-p mutations in formalin-fixed paraffin-embedded tissue samples from 37 patients with penile SCC, 16 patients with cutaneous SCC, and 4 patients with non-neoplastic penile/skin tissue. The expression of p16^INK4a and Ki-67 was investigated via immunohistochemistry. Associations of TERT-p mutation with clinicopathological factors, immunohistochemical results, and clinical outcome were statistically analyzed.

Results

Recurrent TERT-p mutations were identified in 18 out of 37 (48.6%) penile SCCs, including all 3 carcinoma in situ cases. TERT-p mutations were significantly more frequent in non-human papilloma virus (HPV)-related penile SCC types than in non-HPV-related penile SCC based on both histologic classification and p16^INK4a immunoreactivity. Furthermore, TERT-p mutation was associated with a low histologic grade, low mitotic count, absence of necrosis, low Ki-67/MIB-1 labeling index, and absence of lymph node or distant metastasis.

Conclusion

Our study shows TERT-p mutations are the most frequent somatic mutations in penile SCC. In addition, TERT-p mutations are far more frequent in non-HPV-related penile SCC than in HPV-related penile SCC, indicating TERT-p mutations may have a role in tumorigenesis distinct from HPV-related penile SCC.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00432-021-03514-9.

Multitarget fluorescence in situ hybridization diagnostic applications in solid and hematological tumors

Introduction: Multitarget FISH (mFISH) is a technique allowing for simultaneous detection of multiple targets sequences on the same slide through the choice of spectrally distinct fluorophore labels. The mFISH could represent a useful tool in the field of precision oncology.Areas covered: This review discusses the potential applications of mFISH technology in the molecular diagnosis of different solid and hematological tumors, including non-small cell lung cancers, melanomas, renal cell carcinomas, bladder carcinomas, germ cell tumors, and multiple myeloma, as commonly required in the clinical practice.Expert Opinion: In this emerging era of the tailored therapies and newer histo-molecular classifications, there are increasing numbers of predictive and diagnostic biomarkers required for effective clinical care. The mFISH approach may have several applications in the common clinical practice, improving the molecular diagnosis in terms of time, cost and preservation of biomaterial for tumors with a limited amount of tumor available. The mFISH provides several advantages compared to other high-throughput technologies; however, it requires high level of expertise required to interpret complex results.

Without Missing a Beat: Absence of Cilia Informs the Diagnosis of Histopathologically Challenging Spitzoid Melanocytic Neoplasms

The diagnosis of Spitzoid melanocytic lesions remains a formidable challenge in dermatopathology. Numerous ancillary tests have evolved to improve accurate classification of histopathologically ambiguous lesions. A study by Lang et al. (2020b) demonstrates loss of primary cilia in Spitzoid melanoma compared with Spitz nevi and positions ciliation index as an informative ancillary test for Spitzoid lesions.

Clinical, morphologic, and genomic findings in ROS1 fusion Spitz neoplasms

The presence of a characteristic chimeric fusion as the initiating genomic event is one defining feature of Spitz neoplasms. Characterization of specific subtypes of Spitz neoplasms allows for better recognition facilitating diagnosis. Data on clinical outcomes of the specific tumor types may help in predicting behavior. In this study we present the largest series to date on ROS1 fusion Spitz neoplasms. We present the clinical, morphologic, and genomic features of 17 cases. We compared the morphologic features of these 17 cases to a cohort of 99 other non-ROS1 Spitz neoplasms to assess for features that may have high specificity for ROS1 fusions. These tumors consisted of ten Spitz nevi and seven Spitz tumors. None of the cases met criteria for a diagnosis of Spitz melanoma. Morphologically, the ROS1 fusion tumors of this series were characterized by a plaque-like or nodular silhouette, often densely cellular intraepidermal melanocyte proliferation, frequent pagetosis, tendency toward spindle cell cytomorphology, low grade nuclear atypia, and floating nests with occasional transepidermal elimination. However, there was a significant range in microscopic appearances, including two cases with morphologic features of a desmoplastic Spitz nevus. Different binding partners to ROS1 were identified with PWWP2A and TPM3 being the most common. No case had a recurrence or metastasis. Our findings document that most ROS1 fusion Spitz neoplasms have some typical characteristic microscopic features, while a small proportion will have features overlapping with other genomic subtypes of Spitz neoplasms. Preliminary evidence suggests that they tend to be indolent or low grade neoplasms.

ESP, EORTC, and EURACAN Expert Opinion: practical recommendations for the pathological diagnosis and clinical management of intermediate melanocytic tumors and rare related melanoma variants

The recent WHO classification of skin tumors has underscored the importance of acknowledging intermediate grade melanocytic proliferations. A multistep acquisition of oncogenic events drives the progressive transformation of nevi into melanomas. The various pathways described are modulated by the initial oncogenic drivers that define the common, blue, and Spitz nevi groups. Intermediate lesions are most often the result of a clonal evolution within such nevi. Based on this established classification, we have suggested for each pathway a practical diagnostic approach, benefiting from the recently developed molecular tools, both in the setting of general pathology labs and expert centers. Moreover, recommendations regarding the re-excision and clinical follow-up are given to support decision-making in multidisciplinary tumor boards.

Spitz Tumors With ROS1 Fusions: A Clinicopathological Study of 6 Cases, Including FISH for Chromosomal Copy Number Alterations and Mutation Analysis Using Next-Generation Sequencing

Spitz tumors represent a heterogeneous group of melanocytic neoplasms with a spectrum of biological behavior ranging from benign (Spitz nevus) to malignant (spitzoid melanoma). Prediction of the behavior of these lesions based on their histological presentation is not always possible. Recently, mutually exclusive activating kinase fusions, involving ALK, NTRK1, NTRK3, RET, MET, ROS1, and BRAF, have been found in a subset of spitzoid lesions. Some of these genetic alterations were associated with specific morphological features. Here, we report the histological presentation of 6 Spitz tumors with ROS1 fusion. The age of the patients ranged from 6 to 34 years, with strong female prevalence (5:1). All neoplasms were compound melanocytic proliferations with a predominant dermal growth but a conspicuous junctional component displaying atypical microscopic features qualifying them as atypical Spitz tumor. FIP1L1 and CAPRIN1 were identified as 2 novel 5'-fusion partners of ROS1 along with the known PWWP2A-ROS1 fusion. FISH for copy number changes of 9p21, 6p25, and 11q13 was negative in all but 1 neoplasm harboring isolated gain of 8q24. TERT-promoter hotspot mutation analysis was negative in all tumors. All patients are disease-free after a mean follow-up period of 30 months. It is concluded that ROS1-fused spitzoid neoplasms seem to have no distinctive histopathological features although consistent findings were spindled melanocytes arranged in confluent whorling nests, prominent transepidermal elimination of melanocytic nests, and myxoid/mucinous changes.

Metastatic PRAME-Expressing Juvenile Spitzoid Melanoma on the Buttock

Since the cost of molecular biological methods for Spitzoid neoplasms is expensive, the number of institutes that employ these methods might be limited. Preferentially expressed antigen in melanoma (PRAME) is a tumor-associated antigen that is useful to distinguish melanoma from other melanocytic disorders, including pediatric Spitzoid tumors that are difficult to diagnose by conventional methods alone. In this report, we report a case of PRAME-expressing juvenile Spitzoid melanoma with lymph node metastasis. Unexpectedly, there were few PRAME-expressing cells in the primary tumor, whereas most metastatic tumors expressed PRAME in the metastatic lymph node. These observations might suggest that, in Spitzoid melanomas, a limited number of melanoma cells possess metastatic potential and that metastatic lesions possess clonality.

Pathology-based Biomarkers Useful for Clinical Decisions in Melanoma

The dramatic recent advances in therapy of melanoma require a more personalized and precise diagnostic approach to aid in clinical decisions. Tissue-based biomarkers in pathology have diagnostic, prognostic and predictive relevance. Herein we review the most commonly used pathology-based biomarkers in melanoma. Most of these biomarkers are evaluated through immunohistochemistry (IHC) or fluorescent in situ hybridization (FISH) performed on formalin fixed paraffin embedded tissue (FFPE), and are widely available in clinical pathology laboratories. We describe the utility of MART1/Ki67, p16, PRAME, markers of lymphovascular invasion (D2-40, CD31, D2-40/MITF, CD31/SOX-10), BRAF V600E, NRAS, KIT, BAP1, ALK, NTRK, PD-L1, TERT, PTEN, iNOS, and MMR proteins (MLH1, MSH2, MSH6, PMS2) in the evaluation of melanoma specimens. Correct interpretation and awareness of the significance of these biomarkers is crucial for pathologists, dermatologists, and oncologists who take care of melanoma patients.

BRAF fusion Spitz neoplasms; clinical morphological, and genomic findings in six cases

BACKGROUND

Fusions involving the BRAF gene are responsible for 5% of Spitz neoplasms. To better characterize them, we report the clinical, morphological, and genomic findings of six BRAF fusion Spitz tumors.

METHODS

The morphological, clinical, and molecular findings of six BRAF fusion Spitz neoplasms assessed by next generation sequencing (NGS) were compared to a control set of Spitz without BRAF fusions.

RESULTS

BRAF fusion Spitz tumors had frequent predominance of epithelioid morphology (4/6 cases), frequent high-grade nuclear atypia and pleomorphism (5/6 cases), and a frequent desmoplastic base (3/6 cases). Five of six cases were diagnosed as atypical Spitz tumor and one as Spitz nevus. All cases had uneventful clinical follow-up. There were five different fusion partners, with CLIP2 being the most frequent. Secondary pathogenic mutations were frequent and chromosomal copy number changes were seen in three of six cases by an NGS platform.

CONCLUSIONS

BRAF fusions Spitz usually have epithelioid morphology, high-grade nuclear atypia, and desmoplasia. Chromosomal copy number changes are not infrequent. While our cases had uneventful follow-up, a meta-analysis of the literature suggests that among the fusion subtypes associated with Spitz tumors, they are among the subgroups more likely to develop distant metastasis.