Spitz melanoma with MAP3K8::ABLIM1 rearrangement: a case report with review of the literature.

BACKGROUND: Spitz tumors are relatively uncommon melanocytic lesions, typically affecting a relatively younger population but can be encountered at any age. They are characterized by a proliferation of melanocytes with epithelioid and/or spindled cytomorphology features, and interpretation is often challenging. The majority of these tumors are driven by kinase fusions or HRAS mutations. MAP3K8 fusions, although rare, are characteristic genomic events in Spitz tumors, especially in more atypical or malignant lesions. CASE PRESENTATION: Here, we present the case of a 43-year-old woman with a clinically cystic mass in her right groin, histologically characterized as a spindle and epithelioid cell malignant tumor. Immunohistochemistry revealed diffuse expression of S100 protein, tyrosinase and SOX10, patchy weak PRAME, HMB45 and Melan-A reactivity, and negative staining for BRAF V600E. Next-generation sequencing analysis revealed the presence of a MAP3K8::ABLIM1 fusion gene, as well as GRIN2A and TERT promoter mutations. The morphology, immunohistochemistry and molecular analysis confirmed Spitz melanoma with molecular features suggesting a worse prognosis. CONCLUSION: This case introduces a novel fusion partner of MAP3K8 in the context of Spitz melanoma and expands the morphologic and molecular spectrum of Spitz melanoma.

Clinical features and outcomes of paediatric Spitz-type lesions.

INTRODUCTION AND OBJECTIVES: No definitive management guidelines exist for Spitz-type lesions; recommendations in the UK favour a 'safe' approach with a low threshold for excision. We aimed to describe Spitz-type lesions in children to further clarify the clinical features and outcomes. METHODS: We conducted a retrospective cohort study in Addenbrooke's Hospital, Cambridge, UK, and reviewed all patients aged ≤18 years with histologically confirmed Spitz-type lesions from November 2014 to September 2020. Information collected included patient demographics, lesion details, follow-up, outcomes and recurrence. RESULTS: Ninety-one children (male: female 42: 49; mean age at diagnosis: 9.4 years, SD: 4.6 years) were identified. Among them, 64 (70.3%) had classic Spitz or spitzoid naevi, 26 (28.6%) atypical Spitz tumours and 1 (1.1%) had spitzoid malignant melanoma based on histological features. On assessing the clinical features, where documented, we found that 22.0% (20/91) had amelanosis, 44.0% (40/91) had a raised bump, 12.1% (11/91) displayed bleeding, 25.0% (20/80) had non-uniform colour, 96.7% (88/91) were de novo lesions, 55.1% (43/78) were evolving in size and 35.9% (28/78) were evolving in colour. Fifty-nine patients (64.8%) were discharged without the need for follow-up, and the other 32 had a median follow-up time of 4 months. After confirmed excision, no incidences of local recurrence, distant metastases or mortality have been reported to date in all patients. CONCLUSIONS: The outcomes for paediatric Spitz-type lesions continue to be exceptionally good, remaining a low-risk lesion, which is more likely to be benign in children. Hence, we do not advocate aggressive management strategies for paediatric patients with clinically banal Spitz-type lesions.

[ALK rearranged Spitz melanocytoma: a clinicopathological and molecular genetic analysis of two cases].

Objective: To investigate the clinicopathological, immunohistochemical and molecular characteristics of cutaneous ALK-rearranged Spitz melanocytoma. Methods: Two cases of cutaneous ALK-rearranged Spitz melanocytoma from outside hospital consultations in Department of Pathology, Affiliated Cancer Hospital of Fudan University in August 2020 and in Shanghai Ackermann Medical Laboratory in June 2022 were collected. The clinicopathological features, immunophenotypes and molecular profiles of two patients with cutaneous Spitzoid melanocytic tumor harboring ALK-rearrangement were analyzed. The literatures were reviewed. Results: The study included an 8-year-old boy and an 11-year-old girl, who presented with a polypoid lesion in the skin of right thigh and left auricle measuring 1.0 cm and 1.2 cm, respectively. Histologically, they were composed of medium to large-sized epithelioid to plump spindle cells, arranged in nested, plexiform or fascicular patterns in the superficial dermis. The neoplastic cells had abundant eosinophilic cytoplasm with round to ovoid vesicular nuclei containing prominent eosinophilic nucleoli. One case showed mild to moderate nuclear pleomorphism and mitotic activity (average, 2/mm2). Immunohistochemically, the epithelioid and plump spindle cells showed diffuse and strong staining of S-100 protein, SOX10, and ALK (D5F3 and 1A4), but did not express HMB45, PNL2 and MiTF. ALK-rearrangement was detected by fuorescence in situ hybridization in both cases. Subsequent next generation sequence (NGS) analysis identified KANK1::ALK and TPM3:ALK fusions. At 34 and 14 months after surgical resection, both patients remained well with no signs of recurrence or metastasis. Conclusions: ALK-rearranged Spitz melanocytoma represents a morphologically and genetically distinct subset of Spitz melanocytoma, characterized clinically by predilection in children and adolescents, with Spitzoid morphology in plexiform pattern, positive immunohistochemical stains, and rearrangement of ALK. As some cases show atypical features and high mitotic activity, a distinction from Spitz melanoma is warranted.

The elusive BAP1 mutation in pediatric melanocytic tumors.

Cutaneous BAP1-inactivated melanocytomas (BIM) are melanocytic proliferations defined histopathologically by an epithelioid, predominantly dermal melanocytic proliferation with loss of BAP1, and have been largely characterized in adult patients but less well-described in pediatric cohorts. BIM share overlapping histological features with those seen in Spitz nevi; however, unlike Spitz nevi, the majority of BIM carry both BAP1 and BRAFV600E mutations. This study investigated the potential overlap of BIMs with pediatric Spitz nevi by performing immunohistochemical staining of BAP1 and BRAFV600E on pediatric melanocytic tumors with banal Spitz and dermal features. None of the stained tumors in our study exhibited the concurrent BAP1 loss and BRAFV600E positivity that are characteristic of adult BIM, suggesting that this is a low-frequency mutation among banal tumors in the pediatric population.

Spitz Melanoma With SLC20A1::ALK Fusion: A Novel Fusion Previously Undescribed in Spitz Melanocytic Neoplasm.

ABSTRACT: Spitz melanocytic neoplasms exhibit frequent chromosomal rearrangements leading to recurring gene fusions, such as ALK fusions. TPM3 and DCTN1 emerge as the predominant fusion partners of ALK , although less common partners such as NPM1 , TPR , CLIP1 , GTF3C2 , MLPH , EEF2 , MYO5A , and KANK1 have also been documented. Although ALK fusions are primarily associated with Spitz nevi or atypical Spitz tumors, instances of Spitz melanoma with ALK fusions documented in the English literature are exceedingly rare. Here, we present a case of Spitz melanoma harboring SLC20A1::ALK fusion, highlighting a novel fusion transcript not previously reported in Spitz melanocytic neoplasms, including Spitz melanomas. In addition, the tumor exhibits multiple aberrant chromosomal alterations characteristic of melanoma, along with a somatic mutation in GRM3 .

Comparative Performance Analysis of Idylla and Archer in the Detection of Gene Fusions in Spitzoid Melanocytic Tumors.

Melanocytic neoplasms with spitzoid histomorphology are often difficult to classify without identifying genetic drivers such as kinase fusions. Traditional diagnostic methods, such as immunohistochemistry, can yield inconclusive results, and advanced techniques such as the Archer fusion assay are often inaccessible and costly. The Idylla GeneFusion Assay might offer a rapid and cost-effective alternative. This study compared Idylla and Archer in identifying ALK, pan-NTRK, RET, and ROS1 gene fusions. Of the 147 samples where next-generation sequencing did not detect genetic drivers, 89 (60.5%) meeting the tissue requirements were further analyzed using Idylla (Cohort A). Idylla demonstrated a sensitivity of 75% and a specificity of 100% in detecting these fusions. Additionally, among 27 randomly selected cases (Cohort B) that failed to meet the inclusion criteria, Idylla maintained the same levels of sensitivity and specificity. Our findings also show that Idylla can be effectively conducted with isolated RNA, broadening its applicability beyond tissue samples. Although the Idylla assay may not replace more comprehensive molecular assays such as Archer, it could serve as a valuable initial screening tool in diagnosing spitzoid melanocytic tumors.

Clinical, Morphological and Molecular Features of Spitz tumors.

Spitz tumors represent a heterogeneous group of challenging melanocytic neoplasms, displaying a range of biological behaviors, spanning from benign lesions, Spitz nevi (SN) to Spitz melanomas (SM), with intermediate lesions in between known as atypical Spitz tumors (AST). They are histologically characterized by large epithelioid and/or spindled melanocytes arranged in fascicles or nests, often associated with characteristic epidermal hyperplasia and fibrovascular stromal changes. In the last decade, the detection of mutually exclusive structural rearrangements involving receptor tyrosine kinases ROS1, ALK, NTRK1, NTRK2, NTRK3, RET, MET, serine threonine kinases BRAF and MAP3K8, or HRAS mutation, led to a clinical, morphological and molecular based classification of Spitz tumors. The recognition of some reproducible histological features can help dermatopathologist in assessing these lesions and can provide clues to predict the underlying molecular driver. In this review, we will focus on clinical and morphological findings in molecular Spitz tumor subgroups.

Melanoma in Pediatric and Young Adult Patients.

PURPOSE OF REVIEW: Melanoma in younger individuals has different clinical presentations, histologic characteristics and prognosis from older patients. This review summarizes key differences and important new insights into pediatric and young adult melanoma, as well as recent evolutions in treatment. RECENT FINDINGS: Molecular techniques have improved the classification of melanocytic neoplasms, and are especially useful in the workup of the diagnostically challenging lesions frequent in this age group. Molecular evaluation highlights differences between melanoma and atypical lesions with Spitz-like morphology, and should routinely be incorporated for diagnosing and classifying Spitzoid melanocytic to guide prognostication and treatment. Once diagnosed, the management of bona fide melanoma in children and young adults is largely similar to older patients, while the optimal management of lesions such as atypical Spitz tumors remains uncertain. Increased awareness of the presentation and diagnostic characteristics of melanoma in young individuals will allow earlier detection, and improved diagnostic techniques will allow optimum management without over- or under-treatment.

Histological interpretation of spitzoid tumours: an extensive machine learning-based concordance analysis for improving decision making.

The histopathological classification of melanocytic tumours with spitzoid features remains a challenging task. We confront the complexities involved in the histological classification of these tumours by proposing machine learning (ML) algorithms that objectively categorise the most relevant features in order of importance. The data set comprises 122 tumours (39 benign, 44 atypical and 39 malignant) from four different countries. BRAF and NRAS mutation status was evaluated in 51. Analysis of variance score was performed to rank 22 clinicopathological variables. The Gaussian naive Bayes algorithm achieved in distinguishing Spitz naevus from malignant spitzoid tumours with an accuracy of 0.95 and kappa score of 0.87, utilising the 12 most important variables. For benign versus non-benign Spitz tumours, the test reached a kappa score of 0.88 using the 13 highest-scored features. Furthermore, for the atypical Spitz tumours (AST) versus Spitz melanoma comparison, the logistic regression algorithm achieved a kappa value of 0.66 and an accuracy rate of 0.85. When the three categories were compared most AST were classified as melanoma, because of the similarities on histological features between the two groups. Our results show promise in supporting the histological classification of these tumours in clinical practice, and provide valuable insight into the use of ML to improve the accuracy and objectivity of this process while minimising interobserver variability. These proposed algorithms represent a potential solution to the lack of a clear threshold for the Spitz/spitzoid tumour classification, and its high accuracy supports its usefulness as a helpful tool to improve diagnostic decision-making.

Spitz tumour with ALK rearrangement: A case report and literature review.

Spitz tumour with ALK rearrangement is a recently described entity and a rare tumour. The incidence of Spitz tumour was estimated at 3.63 per 100,000 persons in American paediatric population; while there is no data in Asian population. Here we reported a case of an eleven-year-old Asian boy who presented with a left shin nodule of two months' duration. The skin biopsy revealed a Spitz tumour with predominantly spindle cell morphology arranged in fascicles, vertically orientated nests and radial growth pattern. Junctional component, melanin pigment or Kamino bodies were not identified. Immunohistochemical study displayed homogenous cytoplasmic staining for ALK. Fluorescence in-situ hybridisation (FISH) analysis confirmed ALK rearrangement. Review of the literatures demonstrated that positive ALK immunohistochemistry may not correlate with ALK rearrangement. ALK-rearranged Spitz tumour confirmed with FISH analysis favour clinically benign behaviour despite atypical histomorphology or positive sentinel lymph node. Therefore, correlation of histomorphology, immunohistochemical stain and molecular study are important for the definitive diagnosis of this entity.

Amplification of Mutant NRAS in Melanocytic Tumors With Features of Spitz Tumors.

NRAS activating mutations are prevalent in melanocytic neoplasia, occurring in a subset of common acquired melanocytic nevi and ∼30% of cutaneous melanomas. In this study, we described a cohort of 7 distinctive melanocytic tumors characterized by activating point mutations in codon 61 of NRAS with amplification of the mutant NRAS allele and shared clinicopathologic features. These tumors occurred predominantly in younger patients, with a median age of 20 years (range, 6-56 years). They presented as papules on the helix of the ear (4 cases) or extremities (3 cases). Microscopically, the tumors were cellular, relatively well-circumscribed, compound, or intradermal proliferations. The tumor cells often extended into the deep reticular dermis and involved the superficial subcutaneous fat in some cases. The melanocytes were epithelioid to spindled with moderate amounts of cytoplasm and conspicuous nucleoli. They were arranged in short plexiform fascicles, nests, and cords. Some cases had occasional pleomorphic and multinucleated melanocytes. Rare dermal mitotic figures were present in all cases. The dermis contained thick collagen bundles and minimal solar elastosis. Follow-up data were available for 5 patients, with a median period of 4.2 years (range, 1-9 years), during which no recurrences or metastases were reported. Our series highlights a clinicopathologically and molecularly distinctive subset of NRAS-mutated tumors with amplification of the mutant NRAS allele.

Spitz melanocytic neoplasms with MLPH::ALK fusions: Report of two cases with previously unreported features and literature review.

ALK-fused Spitz melanocytic neoplasms are a distinct subgroup of melanocytic lesions exhibiting unique histopathologic characteristics. These lesions often manifest as exophytic or polypoid tumors, characterized by fusiform-to-epithelioid melanocytes arranged in a nested, fascicular, or plexiform growth pattern. Several fusion partners of the ALK gene have been identified in spitzoid melanocytic neoplasms, with TPM3 and DCTN1 being the most prevalent. Less common fusion partners include NPM1, TPR, CLIP1, GTF3C2, EEF2, MYO5A, KANK1, and EHBP1. The MLPH gene, which encodes melanophilin (MLPH), playing a crucial role in regulating skin pigmentation by acting as a linker between RAB27A and myosin Va during melanosome transport, has also recently been recognized as a rare fusion partner of ALK in Spitz melanocytic neoplasms. Currently, there exists a sparse documentation within English literature, illustrating a limited number of cases featuring MLPH::ALK fusion in Spitz melanocytic neoplasms. In this report, we present two additional cases, including a previously unreported instance of Spitz melanoma, contributing to the expanding knowledge on ALK-fused Spitz melanocytic neoplasms. In addition, we provide a comprehensive review of the clinical, histopathologic, and molecular features observed in documented cases with this novel fusion.

Restrospective reappraisal of the prognostic classification of spitzoid melanocytic neoplasms after BRAF and NRAS mutation characterisation: a single institution experience.

AIMS: The current WHO classification of melanocytic tumours excludes neoplasms showing BRAF or NRAS mutations from the Spitz category. This study aimed to review and reclassify atypical melanocytic tumours with spitzoid morphological features diagnosed between 2009 and 2021 in our hospital after expanding the molecular profile, including BRAF and NRAS mutations in all cases. METHODS AND RESULTS: A total of 71 neoplasms showing spitzoid features (Spitz-like) and atypia were included. The risk of progression of tumours was first studied by integrating the morphology, immunohistochemistry (p16, Ki67, HMB45 and PRAME) and fluorescence in-situ hybridisation (FISH) results (melanoma multiprobe and 9p21). In a second step, after expanding the molecular study, including BRAF and NRAS mutational status, the neoplasms were finally classified into four subgroups: atypical Spitz tumour (AST, n = 45); BRAF-mutated naevus/low-grade melanocytoma with spitzoid morphology (BAMS, n = 2); Spitz melanoma (SM, n = 14); and BRAF or NRAS mutated melanoma with spitzoid features (MSF, n = 10). Follow-up of patients revealed uneventful results for AST and BAMS. Only one SM presented lymph node metastasis after 134 months. Conversely, patients with MSF showed an unfavourable outcome: three developed lymph node metastases after a mean time of 22 months, with one patient presenting distant metastasis and dying of the disease 64 months from diagnosis. The progression-free survival showed significant differences between the four groups of spitzoid tumours (P < 0.001) and between both melanoma subtypes (P = 0.012). CONCLUSIONS: The classification and prognostication of atypical neoplasms with spitzoid features requires the integration of histomorphology with the molecular investigation of tumours, which should include BRAF and NRAS mutational status.

Multiple Flesh-Colored Nodules: A Patient with Multiple BAP 1-Inactivated Melanocytic Tumors.

A 22-year-old man without previously known skin disease presented with multiple asymptomatic, skin-brown to red-brown papules on the head and neck for 1 year (Figure 1). The diagnoses considered included benign intradermal or compound nevi, atypical nevi, and neurofibromas. Shave biopsies of three lesions revealed intradermal melanocytic lesions comprising large epithelioid melanocytes flanked by small banal melanocytes (Figure 2). All nevi had a low proliferation index, absent junctional component as demonstrated by a dual Ki-67/Mart-1 immunostain, and no dermal mitotic figures. Immunostaining demonstrated lesional melanocytes positive for p16, but the larger epithelioid melanocytes in these lesions lacked nuclear expression of ubiquitin carboxyl-terminal hydrolase protein (BAP-1; Figure 3). The diagnosis of a BAP-1-inactivated nevus was made, and the patient was referred for genetic counseling and screening for associated malignancies. Given that the lesions involved deep margins, the same were completely excised.

Follicular colonization in melanocytic nevi and melanoma: A literature review.

The lentiginous spread of melanocytes into the hair follicle can be observed in a number of benign melanocytic neoplasms such as in nevi but also in sun-induced melanocytic hyperplasia and melanoma. The follicular colonization by melanocytes in melanoma is classified into three distinct patterns: primary follicular melanoma, melanoma with folliculotropism, and invasive melanoma arising from melanoma in situ with folliculotropism. The role of follicular colonization in melanoma pathologic staging is still a matter of debate though the description of the latter has been recommended by the International Collaboration on Cancer Reporting. In this review, we will discuss the role of follicular colonization in melanoma and melanocytic nevi as well as the facts and controversies regarding this topic.

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.

Biology and genetics of acquired and congenital melanocytic naevi.

Acquired and congenital melanocytic naevi are common benign neoplasms. Understanding their biology and genetics will help clinicians and pathologists correctly diagnose melanocytic tumours, and generate insights into naevus aetiology and melanomagenesis. Genomic data from published studies analysing acquired and congenital melanocytic naevi, including oncogenic driver mutations, common melanoma associated mutations, copy number aberrations, somatic mutation signature patterns, methylation profile, and single nucleotide polymorphisms, were reviewed. Correlation of genomic changes to dermoscopic features, particular anatomic sites and total body naevus counts, was also performed. This review also highlights current scientific theories and evidence concerning naevi growth arrest. Acquired and congenital melanocytic naevi show simple genomes, typically characterised by mutually exclusive single oncogenic driver mutations in either BRAF or NRAS genes. Genomic differences exist between acquired and congenital naevi, common and dysplastic naevi, and by dermoscopic features. Acquired naevi show a higher rate of BRAF hotspot mutations and a lower rate of NRAS hotspot mutations compared to congenital naevi. Dysplastic naevi show upregulation of follicular keratinocyte-related genes compared to common naevi. Anatomical locations and DNA signatures of naevi implicates ultraviolet radiation and non-ultraviolet radiation pathways in naevogenesis. DNA driver point mutations in acquired and congenital melanocytic naevi have been well characterised. Future research is required to better understand transcriptional and epigenetic changes in naevi, as well as those regulating naevus growth arrest and cell environment signalling.