Melanocytic Tumors Research Articles

The Gray Zone of Melanocytic Tumors - A Clinical Point of View.

The Gray Zone of Melanocytic Tumors - A Clinical Point of View.

Considerations on The Biologic Gray Zone of Melanocytic Tumors.

Considerations on The Biologic Gray Zone of Melanocytic Tumors.

Primary leptomeningeal melanocytic neoplasms: A clinicopathologic, immunohistochemical, and molecular study of 12 cases

This study investigated the clinicopathological, immunohistochemical, and molecular features of primary leptomeningeal melanocytic neoplasms (LMNs). Twelve LMN cases were retrospectively reviewed. We performed Fluorescence in-situ hybridization (including a 4-probe FISH assay with CDKN2A and MYC assay) and Next-Generation sequencing analyses on available cases. Histologically, 2 tumours were classified as melanocytomas (MC), 2 as intermediate-grade melanocytomas (IMC), and 8 as leptomeningeal melanomas (LMM). Two rare cases of LMM were associated with large plaque-like blue nevus. One MC case was associated with Ota. Ten cases (83.3%) showed melanocytic cells with benign features diffusely proliferating within the meninges. The Ki-67 in three categories differed (MC 0–1%, IMC 0–3%, LMM 3–10%). 57.1% of LMM cases (4/7) were positive for FISH. Nine of 10 tumours harboured activating hotspot mutations in GNAQ, GNA11, or PLCB4. Additional mutations of EIF1AX, SF3B1, or BAP1 were found in 40%, 30%, and 10% of tumours, respectively. During the follow-up (median = 43 months), 5 LMM patients experienced recurrence and/or metastasis, 3 of them died of the disease and the other 2 are alive with the tumour. Our study is by far the first cohort of LMN cases tested by FISH. In addition to morphological indicators including necrosis and mitotic figures, using a combination of Ki-67 and FISH helps to differentiate between IMC and LMM, especially in LMM cases with less pleomorphic features. SF3B1 mutation is first described in 2 cases of plaque-type blue nevus associated with LMM. Patients with SF3B1 mutation might be related to poor prognosis in LMN.

Melan-A immunolabeling in canine extramedullary plasmacytomas.

Histologic diagnosis of less well-differentiated cases of canine extramedullary plasmacytomas (CEMPs) may require immunohistochemical confirmation to discriminate these tumors from other round cells tumors including lymphoma, cutaneous histiocytoma, and amelanotic melanomas. CEMPs are characterized by widespread immunoreactivity for multiple myeloma 1 (MUM1) antigen and λ light chains, while the melanocytic marker melan-A has been reported to yield negative results. Here, 33 randomly selected CEMPs, 20 melanocytomas, and 20 malignant melanomas were immunohistochemically tested for MUM1, melan-A, and PNL2. In addition, CEMPs were examined for PAX5, E-cadherin, CD3, CD18, CD20, S100, as well as λ and κ light chain immunoreactivity. All CEMPs were characterized by labeling for MUM1 and λ light chain, as well as variable immunopositivity for the remaining antibodies. Notably, 13 cases of CEMPs (39.4%) exhibited immunolabeling for melan-A. Melanocytic tumors immunolabeled for melan-A (40/40; 100%) and PNL2 (34/40; 85%). An unexpected cytoplasmic immunoreactivity for MUM1 was observed in 2 melanocytic tumors. Summarized, MUM1 or melan-A immunomarkers alone are not sufficient to differentiate between CEMPs and amelanotic melanomas and should be part of a larger immunopanel including λ light chain, CD20, and PNL2.

A clinical impact study of dermatologists' use of diagnostic gene expression profile testing to guide patient management.

Aim: Cutaneous melanocytic neoplasms with diagnostic and/or clinical ambiguity pose patient management challenges. Methods: Six randomized case scenarios with diagnostic/clinical uncertainty were described with/without a benign or malignant diagnostic gene expression profile (GEP) result. Results: Clinical impact was assessed by reporting the mean increase/decrease of management changes normalized to baseline (n=32 dermatologists). Benign GEP results prompted clinicians to decrease surgical margins (84.2%). Malignant GEP results escalated surgical excision recommendations (100%). A majority (72.2%) reduced and nearly all (98.9%) increased follow-up frequency for benign or malignant GEP results, respectively. There was an overall increase in management plan confidence with GEP results. Conclusion: Diagnostic GEP tests help guide clinical decision-making in a variety of diagnostically ambiguous or clinicopathologically discordant scenarios.

Primary Diffuse Leptomeningeal Melanocytosis: A Rare and Challenging Diagnosis

Primary melanocytic neoplasms of the central nervous system are rare entities and can present in different clinical forms with mild and non-specific symptoms (such as headache and tinnitus) to severe and limiting symptoms (focal deficits and intracranial hypertension), mimicking the most diverse pathologies. In addition to the peculiar changes in imaging tests, diagnosis is always a challenge given the multitude of possible differential diagnoses, including aseptic meningitis. Given this, we bring here the case of a 59-year-old patient who attended care due to headache and vertigo followed by involvement of the cranial nerves and spinal cord, corroborated by physical examination and imaging study suggesting diffuse involvement of the meninges, which was subsequently confirmed by anatomopathological examination as a primary melanocytic neoplasm of the central nervous system but ended up dying due to complications resulting from late diagnosis. The objective of this work is to raise awareness about the possibility of this pathology as a differential diagnosis in these cases where there are often frustrating clinical manifestations but with changes in imaging tests, to enable an early diagnosis and consequently the possibility of a better therapeutic result, in addition to a brief review of the propaedeutic findings of this pathology.

SOX-10 and TRP-1 expression in feline ocular and nonocular melanomas.

In felines, ocular and nonocular melanomas are uncommon tumors that represent a diagnostic challenge for pathologists, especially when amelanotic. To date, the immunohistochemical diagnostic panel in cats is based on specific melanocytic markers (Melan-A and PNL2) and a nonspecific but sensitive marker (S100). In human medicine, SOX-10 is reported to be a sensitive antibody for the detection of melanoma micrometastasis in the lymph node. TRP-1, an enzyme involved in melanogenesis, has recently been used in humans and dogs as a specific melanocyte marker. The aim of this study was to evaluate the cross-reactivity and the expression of SOX-10 and TRP-1 antibodies in feline normal tissue and melanocytic tumors. Thirty-one cases of ocular, cutaneous, and oral melanomas were retrospectively evaluated and confirmed by histopathological examination and by immunolabeling with Melan-A and/or PNL2. SOX-10 nuclear expression in normal tissues was localized in epidermal, subepidermal, hair bulb, and iridal stromal melanocytes and dermal nerves. In melanomas, nuclear expression of SOX-10 was detected in ocular (11/12; 92%), oral (6/7; 86%), and cutaneous sites (12/12; 100%). TRP-1 cytoplasmic immunolabeling in normal tissue was observed in epidermal and bulbar melanocytes and in the lining pigmented epithelium of the iris and in its stroma. Its expression was positively correlated to the degree of pigmentation in the tumor and was observed in 75% of ocular (9/12), 43% of oral (3/7), and 33% of cutaneous melanomas (4/12). This study demonstrated the cross-reactivity of SOX-10 and TRP-1 antibodies in feline non-neoplastic melanocytes and their expression in ocular and nonocular melanomas.

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.

The Impact of Next-generation Sequencing on Interobserver Agreement and Diagnostic Accuracy of Desmoplastic Melanocytic Neoplasms.

Next-generation sequencing (NGS) is increasingly being utilized as an ancillary tool for diagnostically challenging melanocytic neoplasms. It is incumbent upon the pathology community to perform studies assessing the benefits and limitations of these tools in specific diagnostic scenarios. One of the most challenging diagnostic scenarios faced by skin pathologists involves accurate diagnosis of desmoplastic melanocytic neoplasms (DMNs). In this study, 20 expert melanoma pathologists rendered a diagnosis on 47 DMNs based on hematoxylin and eosin sections with demographic information. After submitting their diagnosis, the experts were given the same cases, but this time with comprehensive genomic sequencing results, and asked to render a diagnosis again. Identification of desmoplastic melanoma (DM) improved by 7%, and this difference was statistically significant ( P <0.05). In addition, among the 15 melanoma cases, in the pregenomic assessment, only 12 were favored to be DM by the experts, while after genomics, this improved to 14 of the cases being favored to be DM. In fact, some cases resulting in metastatic disease had a substantial increase in the number of experts recognizing them as DM after genomics. The impact of the genomic findings was less dramatic among benign and intermediate-grade desmoplastic tumors (BIDTs). Interobserver agreement also improved, with the Fleiss multirater Kappa being 0.36 before genomics to 0.4 after genomics. NGS has the potential to improve diagnostic accuracy in the assessment of desmoplastic melanocytic tumors. The degree of improvement will be most substantial among pathologists with some background and experience in bioinformatics and melanoma genetics.

Melanoma of the dog and cat: consensus and guidelines.

Melanoma of the dog and cat poses a clinical challenge to veterinary practitioners across the globe. As knowledge evolves, so too do clinical practices. However, there remain uncertainties and controversies. There is value for the veterinary community at large in the generation of a contemporary wide-ranging guideline document. The aim of this project was therefore to assimilate the available published knowledge into a single accessible referenced resource and to provide expert clinical guidance to support professional colleagues as they navigate current melanoma challenges and controversies. Melanocytic tumors are common in dogs but rare in cats. The history and clinical signs relate to the anatomic site of the melanoma. Oral and subungual malignant melanomas are the most common malignant types in dogs. While many melanocytic tumors are heavily pigmented, making diagnosis relatively straightforward, melanin pigmentation is variable. A validated clinical stage scheme has been defined for canine oral melanoma. For all other locations and for feline melanoma, TNM-based staging applies. Certain histological characteristics have been shown to bear prognostic significance and can thus prove instructive in clinical decision making. Surgical resection using wide margins is currently the mainstay of therapy for the local control of melanomas, regardless of primary location. Radiotherapy forms an integral part of the management of canine oral melanomas, both as a primary and an adjuvant therapy. Adjuvant immunotherapy or chemotherapy is offered to patients at high risk of developing distant metastasis. Location is the major prognostic factor, although it is not completely predictive of local invasiveness and metastatic potential. There are no specific guidelines regarding referral considerations for dogs with melanoma, as this is likely based on a multitude of factors. The ultimate goal is to provide the best options for patients to extend quality of life and survival, either within the primary care or referral hospital setting.

Detection of PD-L1, PD-1 and CTLA-4 by RNA in-situ hybridization in canine oral melanocytic neoplasms and their microenvironment

Detection of PD-L1, PD-1 and CTLA-4 by RNA in-situ hybridization in canine oral melanocytic neoplasms and their microenvironment

Proposal for a new histological grading system for canine oral melanocytic tumoUrs

Proposal for a new histological grading system for canine oral melanocytic tumoUrs

Limitations of the current Equine Melanocytic Tumour classification

limitations of the current Equine Melanocytic Tumour classification

Methylation analysis of LINE-1 elements and morphological nuclear parameters in the differential diagnosis of cutaneous melanocytic tumoUrs in dogs

Methylation analysis of LINE-1 elements and morphological nuclear parameters in the differential diagnosis of cutaneous melanocytic tumoUrs in dogs

BRAF Mutated and Morphologically Spitzoid Tumors, a Subgroup of Melanocytic Neoplasms Difficult to Distinguish From True Spitz Neoplasms.

Drivers of Spitz neoplasms include activating point mutations in HRAS and Spitz-associated genomic fusions. It has become evident that some BRAF -mutated melanocytic neoplasms can morphologically mimic Spitz tumors (STs). These have been termed BRAF mutated and morphologically spitzoid (BAMS). In this study, 17 experts from the International Melanoma Pathology Study Group assessed 54 cases which included 40 BAMS and 14 true STs. The participants reviewed the cases blinded to the genomic data and selected among several diagnostic options, including BAMS, ST, melanoma, and other. A total of 38% of all diagnostic selections in the BAMS cases were for BAMS, whereas 32% were for ST. In 22 of the BAMS cases, the favored diagnosis was BAMS, whereas in 17 of the BAMS cases, the favored diagnosis was ST. Among the 20 cases in the total group of 54 with the highest number of votes for ST, half were BAMS. Of BAMS, 75% had a number of votes for ST that was within the SD of votes for ST seen among true ST cases. There was poor interobserver agreement for the precise diagnosis of the BAMS (kappa = 0.16) but good agreement that these cases were not melanoma (kappa = 0.7). BAMS nevi/tumors can closely mimic Spitz neoplasms. Expert melanoma pathologists in this study favored a diagnosis of ST in nearly half of the BAMS cases. There are BAMS cases that even experts cannot morphologically distinguish from true Spitz neoplasms.

Abstract 2593: Spatial multi-omics profiling of tumor cell phenotypes in primary cutaneous melanoma at single-cell resolution

Abstract Primary cutaneous melanomas develop in stages from melanoma precursor cells that may progress to melanoma in situ (MIS) and eventually to invasive disease. Molecular changes, such as tumor cell state switches from melanocytic to undifferentiated and neural-crest-like phenotypes, have been associated with the development of melanoma metastases and therapeutic resistance. However, it is unknown whether cell states or gene expression changes enriched in advanced tumors exist at the premalignant stage and if they can elicit tumor-infiltrating lymphocytes (TILs). To address this gap, we analyzed a cohort of clinical samples from 43 patients with primary cutaneous melanoma using whole-slide cyclic multiplex immunofluorescence imaging (CyCIF), morphology-guided micro-regional RNA sequencing, and high-resolution 3D imaging. Each specimen contained multiple histologically-distinct regions representing a progression axis from normal to precursor to melanoma in situ to invasion. Subsequently, we examined the molecular profiles of both atypical melanocytes and tumor cells, and the gene expression and tumor microenvironmental (TME) changes that occurred during these progression stages. We identified major intra- and inter-specimen heterogeneity in the tumor intrinsic and extrinsic features across progression stages. Multiple tumor samples contained regions where publicly available gene signatures linked to both melanocytic and undifferentiated cell phenotypes were enriched. CyCIF analysis confirmed that various tumor cell phenotypes can coexist in close proximity to each other in early-stage untreated melanomas, and that the majority of undifferentiated tumor cells were located within regions of dermal invasion. Moreover, the cellular neighborhoods around undifferentiated tumor cells had a higher proportion of CD8+ T cells and cells of myeloid lineage compared to the neighborhoods around melanocytic tumor cell phenotypes. When assessing the localization and abundance of various tumor cell phenotypes, the levels of spatial and regional heterogeneity increased proportionally along normal to premalignant to malignant progression. Furthermore, the regional entropy of tumor cell phenotypes decreased along tumor depth in the majority (63%) of the samples, and even the melanoma in situ regions showed varying levels of spatial heterogeneity. Our in-depth multimodal molecular analyses highlight the presence of spatial heterogeneity among tumor cell phenotypes as well as the organization of early-stage primary melanomas, and are suggestive of tumor cell adaptation to the local environment. Citation Format: Tuulia Vallius, Edward Novikov, Ajit Nirmal Johnson, Shi Yingxiao, Roxanne Pelletier, Shishir Pant, Zoltan Maliga, Alyce Chen, Clarence Yapp, Sabrina Chan, Christine Lian, George F. Murphy, Sandro Santagata, Peter Sorger. Spatial multi-omics profiling of tumor cell phenotypes in primary cutaneous melanoma at single-cell resolution [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2593.

Characterization of PRAME immunohistochemistry reveals lower expression in pediatric melanoma compared to adult melanoma.

Pediatric melanomas are rare tumors that have clinical and histological differences from adult melanomas. In adult melanoma, the immunohistochemical marker PRAME is increasingly employed as a diagnostic adjunct. PRAME is also under investigation as a target structure for next-generation immunotherapies including T-cell engagers. Little is known about the characteristics of PRAME expression in pediatric melanoma. In this retrospective study, samples from 25 pediatric melanomas were compared with control groups of melanomas in young adults (18-30 years; n = 32), adult melanoma (>30 years, n = 30), and benign melanocytic nevi in children (0-18 years; n = 30) with regard to the immunohistochemical expression of PRAME (diffuse PRAME expression >75%/absolute expression). Pediatric melanomas show lower diffuse PRAME expression (4%) and lower absolute PRAME expression (25%) compared to young adult melanomas (15.6%/46.8%) and adult melanomas (50%/70%). A significant age-dependent expression could be observed. An analysis of event-free survival shows no prognostic role for PRAME in pediatric melanoma and young adult melanoma, but a significant association with diffuse PRAME expression in adulthood. The age dependency of PRAME expression poses a potential pitfall in the diagnostic application of melanocytic tumors in young patients and may limit therapeutic options within this age group. The immunohistochemical expression of the tumor-associated antigen PRAME is an increasingly important diagnostic marker for melanocytic tumors and is gaining attention as a possible immunotherapeutic target in melanoma. As the available data primarily stem from adult melanoma, and given the clinical and histological distinctions in pediatric melanomas, our understanding of PRAME expression in this specific patient group remains limited. The age-dependent low PRAME expression shown here constrains the use of this marker in pediatric melanoma and may also limit the use of immunotherapeutic strategies against PRAME in young patients.

Double Immunohistochemical Labelling of PRAME and Melan A in Slow Mohs Biopsy Margin Assessment of Lentigo Maligna and Lentigo Maligna Melanoma.

Introduction: Lentigo maligna (LM) and lentigo maligna melanoma (LMM) predominantly affect the head and neck areas in elderly patients, presenting as challenging ill-defined pigmented lesions with indistinct borders. Surgical margin determination for complete removal remains intricate due to these characteristics. Morphological examination of surgical margins is the key form of determining successful treatment in LM/LMM and underpin the greater margin control provided through the Slow Mohs micrographic surgery (SMMS) approach. Recent assessments have explored the use of immunohistochemistry (IHC) markers, such as Preferentially Expressed Antigen in Melanoma (PRAME), to aid in LM/LMM and margin evaluation, leveraging the selectivity of PRAME labelling in malignant melanocytic neoplasms. Methods: A Novel double-labelling (DL) method incorporating both PRAME and MelanA IHC was employed to further maximise the clinical applicability of PRAME in the assessment of LM/LMM in SMMS biopsies. The evaluation involved 51 samples, comparing the results of the novel DL with respective single-labelling (SL) IHC slides. Results: The findings demonstrated a significant agreement of 96.1% between the DL method and SL slides across the tested samples. The benchmark PRAME SL exhibited a sensitivity of 91.3% in the SMMS specimens and 67.9% in histologically confirmed positive margins. Discussion: This study highlights the utility of PRAME IHC and by extension PRAME DL as an adjunctive tool in the assessment of melanocytic tumours within staged excision margins in SMMS samples.

Diagnostic Discordance Among Histopathological Reviewers for Difficult-to-Diagnose Melanocytic Lesions

Purpose: Histopathological examination is adequate for most melanocytic neoplasms. However, there is a subset of lesions with uncertain malignant potential that are difficult-to-diagnose where utilization of ancillary tests may be considered to aid in providing a more definitive diagnosis.&#x0D; Study design: Under an IRB-approved protocol, 3,317 melanocytic lesions underwent independent diagnostic review by up to 9 unique board-certified dermatopathologists. Each lesion received ≥ 3 diagnoses via electronic whole slide images with zoom-in capability as benign, malignant, or unknown malignant potential (UMP). Lesions were subsequently binned according to the results of dermatopathology review in the following manner: concordant (all diagnoses of the same designation); conflicting (both benign and malignant designations); majority (a single designation with the highest number of diagnoses); and equivocal (equal number of different designations). Here we describe the identification of lesions suitable for ancillary testing.&#x0D; Results: 30% of lesions were concordant benign and 46.3% were concordant malignant, indicating 76.3% of all lesions were not difficult-to-diagnose. 23.7% of lesions had some level of diagnostic difficulty and/or ambiguity defined by disagreement between reviewers and would be suitable for ancillary testing. Within these ~24%, 7.3% of lesions were majority benign, 4.8% of lesions were majority malignant, 2.7% were majority UMP, 6.9% of lesions were conflicting, and 1.6% of lesions were equivocal.&#x0D; &#x0D; Conclusions: We demonstrate that in a large cohort of suspicious pigmented lesions, ~24% were difficult-to-diagnose, supporting the need for additional objective diagnostic tools. Patient care would benefit from ancillary testing to aid the diagnosing pathologist in identification of the most appropriate diagnosis to optimize patient management.&#x0D; Potential conflicts of interest: This study was supported by Castle Biosciences, Inc. GAH and JAP have served as consultants for Castle Biosciences, Inc. MSG is an employee shareholder of Castle Biosciences, Inc. SIE is a consultant and shareholder for Castle Biosciences, Inc. Editorial assistance was provided by Brooke H. Russell, PhD, and Jason H Rogers, MSc, both employee shareholders of Castle Biosciences, Inc.

Cytological, Histopathological and Immunohistochemical Studies on Naturally Occurring Cutaneous Melanomas in Cattle in and Around Namakkal, Tamil Nadu, India

Background: Melanomas are tumours that originate from melanoblasts. The studies on bovine tumours are of clinical concern since some melanocytic tumours are congenital and occur in young animals. The present work was carried out to study the pathomorphological characteristics of melanomas in cattle for early diagnosis and intervention. Methods: Tumour samples were collected from suspected cases of neoplasia from four animals during the study period. Data pertaining to the animals were collected. Fine needle aspiration cytology and impression smear were stained with Giemsa stain. Tissue samples were collected in 10 per cent neutral buffered formalin for histopathological examination. Special staining with Fontana silver stain and immunohistochemistry with Melan- A and S- 100 markers for confirmatory diagnosis of melanin pigment was done. Result: Cytology revealed neoplastic cells with vacuolation and pleomorphism. Cytoplasm contained abundant melanin pigments. Microscopically, the cytoplasm contained abundant brown, black coloured melanin pigment granules. Tissue sections stained with Fontana silver impregnation method revealed the presence of black coloured granules. Immunohistochemistry with Melan-A and S-100 revealed strong expression of brown coloured reaction in the cytoplasm of the neoplastic cells.