The 2023 WHO updates on skin tumors: advances since the 2018 edition.

Pathology is pivotal in diagnosing skin tumors, and the precision of diagnosis is crucial to devise customized treatment plans and enhance patient care in dermatology. The latest edition of the World Health Organization's classification of skin tumors serves as a comprehensive compendium, summarizing and categorizing all recent advancements in both anatomical-pathological and molecular aspects of cutaneous neoplasms. Several relevant advances have been introduced and new entities have been described. While the fundamental structure of the classification remains unchanged, notable additions include three new sections aimed at providing a more exhaustive description of skin lesions: nail unit tumors, skin metastases, and genetic tumor syndromes associated with skin malignancies. Recent strides in molecular pathology have led to significant breakthroughs in decoding the underlying mechanisms of various skin tumors, ranging from adnexal neoplasms to hematolymphoid neoplasms, soft tissue tumors, and melanocytic lesions. Of particular importance is the evolution in our understanding of melanocytic neoplasms, with the introduction of the term "melanocytoma" reserved for lesions exhibiting "intermediate" biological behavior and characterized by specific molecular mutations. The pathologic diagnosis process integrates morphological, immunohistochemical, and molecular features, playing a crucial role in clinical decision-making. The WHO classification serves as a valuable tool in promoting multidisciplinarity in the management of cutaneous neoplasms with the aim of translating novel pathological discoveries into more effective treatments. This review aims to distill the major updates introduced by the new classification, providing a synthesis of the latest scientific insights.

LMNA::NTRK1 and PRDX1::NTRK1 Atypical Spitz Tumor: A Report of Two Additional Cases With Histological, Immunohistochemical, and Molecular Insights.

ABSTRACT: Over the past decade, advancements in molecular biology have contributed to changes in the diagnostic classification of Spitz neoplasms, including Spitz nevi, atypical Spitz tumors, and Spitz melanomas. The recent World Health Organization classification of skin tumors identifies fusion kinases, including NTRK1, NTRK2, and NTRK3, as critical drivers of these lesions. New fusion genes have continued to expand the spectrum of known molecular alterations, particularly within the category of Spitz NTRK-rearranged lesions. We present 2 new cases of NTRK-rearranged Spitz lesions: an atypical Spitz tumor with common LMNA::NTRK1 fusion and an atypical Spitz tumor with a rare PRDX1::NTRK1 fusion. Clinical, histopathological, immunohistochemical, and molecular analyses were performed to diagnose these patients. This report adds to the growing body of knowledge on NTRK-rearranged Spitz lesions and underscores the importance of integrating molecular findings with morphological and immunohistochemical data for the accurate classification and understanding of these neoplasms.

Immune checkpoint inhibitors targeting PD-1/PD-L1 in the treatment of human lymphomas.

Non-Hodgkin lymphomas (NHLs) encompass a diverse group of malignancies arising from B cells, T cells, and natural killer (NK) cells at various stages of differentiation. Conversely, classical Hodgkin lymphomas (cHLs) primarily feature Reed-Sternberg cells (RSCs) amid a background of reactive immune cells. Immunomodulatory pathways, notably the PD-1/PD-L1 axis, play pivotal roles in tumor immune evasion across both NHLs and cHLs. Elevated expression of PD-1 and PD-L1 is observed in a spectrum of lymphomas, influencing prognosis and treatment response. Therapeutically, immune checkpoint inhibitors (ICIs) targeting PD-1/PD-L1 have revolutionized lymphoma management, particularly in relapsed/refractory cases. Nivolumab and pembrolizumab, among others, have demonstrated efficacy in various B-cell lymphomas, with promising outcomes in cHL. Combination strategies incorporating ICIs with conventional chemotherapy or targeted agents show enhanced efficacy and are being explored extensively. In this review we discuss the most important features of the tumor microenvironment of NHLs and cHLs, address the therapeutic approaches with ICIs and try to outline future perspectives.

Epigenetics and Control of Tumor Angiogenesis in Melanoma: An Update with Therapeutic Implications.

Angiogenesis, the formation of new blood vessels from pre-existing ones, is a crucial process in the progression and metastasis of melanoma. Recent research has highlighted the significant role of epigenetic modifications in regulating angiogenesis. This review comprehensively examines the current understanding of how epigenetic mechanisms, including DNA methylation, histone modifications, and non-coding RNAs, influence angiogenic pathways in melanoma. DNA methylation, a key epigenetic modification, can silence angiogenesis inhibitors such as thrombospondin-1 and TIMP3 while promoting pro-angiogenic factors like vascular endothelial growth factor (VEGF). Histone modifications, including methylation and acetylation, also play a pivotal role in regulating the expression of angiogenesis-related genes. For instance, the acetylation of histones H3 and H4 is associated with the upregulation of pro-angiogenic genes, whereas histone methylation patterns can either enhance or repress angiogenic signals, depending on the specific histone mark and context. Non-coding RNAs, particularly microRNAs (miRNAs) further modulate angiogenesis. miRNAs, such as miR-210, have been identified as key regulators, with miR-9 promoting angiogenesis by targeting E-cadherin and enhancing the expression of VEGF. This review also discusses the therapeutic potential of targeting epigenetic modifications to inhibit angiogenesis in melanoma. Epigenetic drugs, such as DNA methyltransferase inhibitors (e.g., 5-azacytidine) and histone deacetylase inhibitors (e.g., Vorinostat), have shown promise in preclinical models by reactivating angiogenesis inhibitors and downregulating pro-angiogenic factors. Moreover, the modulation of miRNAs and lncRNAs presents a novel approach for anti-angiogenic therapy.

The Rarity in the Rarity: Presentation of Three Cases of Cutaneous Carcinosarcoma with Clinical and Histopathological Insights.

A cutaneous carcinosarcoma (cCS) is a rare and aggressive skin cancer characterized by both carcinomatous (epithelial) and sarcomatous (mesenchymal) components, making it a biphasic tumor. Despite its occurrence in various organs, a cCS is exceptionally rare in the skin, predominantly affecting older males. The etiology of a cCS is unclear, but it may originate from a single progenitor cell capable of dual differentiation or from a collision of carcinoma and sarcoma cells. Clinically, a cCS presents as a rapidly growing, painful, ulcerated nodule or plaque on sun-exposed skin, with a high risk of local invasion and metastasis. Histopathologically, a cCS includes various epithelial components, such as squamous cell carcinoma and basal cell carcinoma, along with undifferentiated sarcomatous components resembling atypical fibroxanthoma. The tumor may also exhibit heterologous differentiation like angiosarcomatous or rhabdomyosarcomatous features. We present three cases of a cCS, highlighting their clinical and histological characteristics and comparing them with previously reported cases. Understanding a cCS is complicated by its rarity and diverse presentation, emphasizing the need for further research to elucidate its pathogenesis and optimal management.

Placental ACE2 Expression: A Possible Pathogenetic Mechanism for Infantile Hemangiomas.

ACE2 is a mono-carboxypeptidase with remarkable vasculo-protective properties, and its expression in the human placenta plays a central role in blood pressure homeostasis and fetal perfusion. Therefore, an alteration in the placental expression of ACE2 could be responsible for reduced placental perfusion and infantile hemangioma (IH) development. Study placentae were collected from patients affected by IHs who were referred to our Dermatology Clinic from 2016 to 2022, while control placentae were randomly collected while matching cases for gestational age. Immunohistochemical investigations were performed with a recombinant anti-ACE2 rabbit monoclonal antibody. A total of 47 placentae were examined, including 20 study placentae and 27 control ones. The mean placental weight was significantly lower in the study group (380.6 g vs. 502.3 g; p = 0.005), while subclinical chorioamnionitis occurred more frequently in the study group (20% vs. 0%, p = 0.03). The mean ACE2 expression was dramatically lower in the study group (χ2 = 42.1 p < 0.001), and the mean placental weight was significantly lower when ACE2 was not expressed compared to the 25-75% and >75% classes of expression (p < 0.05). This study demonstrated that ACE2, as a marker for tissue hypoxia, is dramatically hypo-expressed in placentae belonging to mothers who delivered one or more babies with IH compared to the controls.

Mast cell density in Merkel cell carcinoma and its correlation with prognostic features and MCPyV status: a pilot study.

Merkel cell carcinoma (MCC) is a rare, highly aggressive, primitive neuroendocrine carcinoma of the skin, the origin of which is not yet fully understood. Numerous independent prognostic factors have been investigated in an attempt to understand which are the most important parameters to indicate in the histological diagnostic report of MCC. Of these, mast cells have only been studied in one paper before this one. We present a retrospective descriptive study of 13 cases of MCC, received at the Department of Pathology over a 20-year period (2003-2023 inclusive) on which we performed a study using whole-slide (WSI) morphometric analysis scanning platform Aperio Scanscope CS for the detection and spatial distribution of mast cells, using monoclonal anti-tryptase antibody and anti-CD34 monoclonal antibody to study the density of microvessels. In addition, we analyzed MCPyV status with the antibody for MCPyV large T-antigen (Clone CM2B4). We found statistically significant correlation between mast cell density and local recurrence/distant metastasis/death-of-disease (p = 0.008). To our knowledge, we firstly reported that MCPyV ( -) MCC shows higher mast cells density compared to MCPyV ( +) MCC, the latter well known to be less aggressive. Besides, the median vascular density did not show no significant correlation with recurrence/metastasis/death-of-disease, (p = 0.18). Despite the small sample size, this paper prompts future studies investigating the role of mast cell density in MCC.

The Rarity in the Rarity: Presentation of Two Rare and Unusual Cases of Nodular Fasciitis and Proliferative Fasciitis.

Nodular fasciitis (NF) and proliferative fasciitis (PF) are benign, reactive mesenchymal neoplasms that can mimic malignancies due to their rapid growth and histological characteristics. NF typically affects the subcutaneous tissue, occasionally involving muscles and fascia, predominantly in young adults, and appears frequently in the upper extremities, trunk, and head/neck. PF, a pseudosarcomatous lesion, primarily occurs in the subcutaneous tissue of adults aged 40-70 years and is uncommon in younger populations. This article presents two pediatric cases of NF and PF in unusual locations: a six-year-old girl with a vulvar NF and a 10-year-old girl with a gluteal PF. Both cases demonstrated rapid growth and distinct histological features, confirmed by immunohistochemical analyses and fluorescence in situ hybridization (FISH). These cases underscore the importance of accurate histological recognition to avoid misdiagnosis and ensure appropriate treatment, highlighting the rarity of such occurrences in children and the need for awareness among clinicians and pathologists.

Combining Brentuximab Vedotin With Dexamethasone, High-dose Cytarabine, and Cisplatin as Salvage Treatment in Pediatric Relapsed or Refractory Classic Hodgkin Lymphoma: Two Case Reports.

Hodgkin lymphoma (HL) is among the most commonly occurring malignancies in adolescents. For relapsed/refractory disease, many regimens have been proposed. Novel agents are increasingly used, like brentuximab vedotin (BV), an antiCD30 antibody-drug conjugate, used as a single agent or in combination with classic regimens mainly in adults, while limited is the experience in pediatrics. We report here on 2 boys with aggressive and high-risk relapsed HL, successfully treated with the BV plus dexamethasone, high-dose cytarabine, cisplatin regimen as induction salvage treatment. Our experience provides real-world evidence on the use of BV-dexamethasone, high-dose cytarabine, cisplatin as first-line salvage therapy for relapsed/refractory HL and expands the current therapeutic choices.

Dura mater and survival time determination in individuals who died after traumatic brain injury: a preliminary study.

BACKGROUND: Traumatic brain injury (TBI) is one of the major causes of morbidity and mortality among young people and is a matter of concern for forensic pathologists. Many authors have tried to estimate a person's survival time (ST) after TBI using different approaches. OBJECTIVE: The present study aimed to present an innovative workflow to estimate the ST after TBI by observing the inflammatory reaction of the dura mater (DM). METHODS: The authors collected DM samples from 36 cadavers (20 with TBI and 16 with no history or signs of TBI). Each sample was labelled via immunohistochemistry with three different primary antibodies, CD15, CD68, and CD3, yielding 108 slides in total. The slides were digitalized and analysed using QuPath software. RESULTS: The DM is involved in the inflammatory response after TBI. CD15 immunoreactivity allowed us to distinguish between subjects who died immediately after TBI and those with an ST of minutes or hours. CD3 immunoreactivity can be used to differentiate subjects with an ST of days from those with other STs. Moreover, the DM samples showed an acceptable diagnostic yield even in samples with signs of putrefaction.

Angiogenesis Still Plays a Crucial Role in Human Melanoma Progression.

Angiogenesis plays a pivotal role in tumor progression, particularly in melanoma, the deadliest form of skin cancer. This review synthesizes current knowledge on the intricate interplay between angiogenesis and tumor microenvironment (TME) in melanoma progression. Pro-angiogenic factors, including VEGF, PlGF, FGF-2, IL-8, Ang, TGF-ß, PDGF, integrins, MMPs, and PAF, modulate angiogenesis and contribute to melanoma metastasis. Additionally, cells within the TME, such as cancer-associated fibroblasts, mast cells, and melanoma-associated macrophages, influence tumor angiogenesis and progression. Anti-angiogenic therapies, while showing promise, face challenges such as drug resistance and tumor-induced activation of alternative angiogenic pathways. Rational combinations of anti-angiogenic agents and immunotherapies are being explored to overcome resistance. Biomarker identification for treatment response remains crucial for personalized therapies. This review highlights the complexity of angiogenesis in melanoma and underscores the need for innovative therapeutic approaches tailored to the dynamic TME.

Autoimmunity in thymic epithelial tumors: a not yet clarified pathologic paradigm associated with several unmet clinical needs.

Thymic epithelial tumors (TETs) are rare mediastinal cancers originating from the thymus, classified in two main histotypes: thymoma and thymic carcinoma (TC). TETs affect a primary lymphoid organ playing a critical role in keeping T-cell homeostasis and ensuring an adequate immunological tolerance against "self". In particular, thymomas and not TC are frequently associated with autoimmune diseases (ADs), with Myasthenia Gravis being the most common AD present in 30% of patients with thymoma. This comorbidity, in addition to negatively affecting the quality and duration of patients' life, reduces the spectrum of the available therapeutic options. Indeed, the presence of autoimmunity represents an exclusion criteria for the administration of the newest immunotherapeutic treatments with checkpoint inhibitors. The pathophysiological correlation between TETs and autoimmunity remains a mystery. Several studies have demonstrated the presence of a residual and active thymopoiesis in adult patients affected by thymomas, especially in mixed and lymphocytic-rich thymomas, currently known as type AB and B thymomas. The aim of this review is to provide the state of art in regard to the histological features of the different TET histotype, to the role of the different immune cells infiltrating tumor microenvironments and their impact in the break of central immunologic thymic tolerance in thymomas. We discuss here both cellular and molecular immunologic mechanisms inducing the onset of autoimmunity in TETs, limiting the portfolio of therapeutic strategies against TETs and greatly impacting the prognosis of associated autoimmune diseases.

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.

Could MRONJ Be Related to Osimertinib Monotherapy in Lung Cancer Patients after Denosumab Suspension?

BACKGROUND: Medication-related osteonecrosis of the jaws is the most frequent complication in patients treated or in therapy with antiresorptive/antiangiogenetic drugs. The list of medications possibly related to MRONJ onset is constantly growing; we aimed to report on a third-generation epidermal growth factor receptor tyrosine kinase inhibitor (Osimertinib) as possibly responsible for bilateral maxillary necrosis onset in the herein-described case. METHODS: In June 2023, an oncologic patient with two different maxillary bone exposures was referred to our attention. His medical history revealed a two-year Denosumab regimen along with Osimertinib, the latter not suspended before teeth extractions. The clinicians performed a sequestrum removal and bone debridement after three cycles of antibiotic therapy. RESULTS: Histologic examinations confirmed the clinical diagnosis of MRONJ excluding a metastatic occurrence, while complete mucosal healing was achieved after 15 days. CONCLUSIONS: The patient suspended Denosumab for more than six months before teeth extraction for MRONJ prevention; hence, failure to discontinue Osimertinib led us to consider it a possible etiological factor. From a literature analysis, only one case has already been published reporting a possible Osimertinib-related occurrence of MRONJ in lung cancer patients. Our case is a further report that could be intended as an alert both for oncologists and dentists to share decisions about the oral management of such patients together, also informing them about this possible risk. Also, this report could trigger in the scientific community the necessity to evaluate further guidelines for similar doubtful cases in which the drug interaction, the mono-suspension, and the possible removable prosthesis-related additional trauma should be considered causes or con-causes.

PRAME Is an Effective Tool for the Diagnosis of Nevus-Associated Cutaneous Melanoma.

(1) Background: Nevus-associated cutaneous melanoma (CM) is relatively common in the clinical practice of dermatopathologists. The correct diagnosis and staging of nevus-associated cutaneous melanoma (CM) mainly relies on the correct discrimination between benign and malignant cells. Recently, PRAME has emerged as a promising immunohistochemical marker of malignant melanocytes. (2) Methods: PRAME immunohistochemistry (IHC) was performed in 69 cases of nevus-associated CMs. Its expression was evaluated using a score ranging from 0 to 4+ based on the percentage of melanocytic cells with a nuclear expression. PRAME IHC sensitivity, specificity, positive predictive values, and negative predictive values were assessed. Furthermore, the agreement between morphological data and PRAME expression was evaluated for the diagnosis of melanoma components and nevus components. (3) Results: PRAME IHC showed a sensitivity of 59%, a specificity of 100%, a positive predictive value of 100%, and a negative predictive value of 71%. The diagnostic agreement between morphology and PRAME IHC was fair (Cohen's Kappa: 0.3); the diagnostic agreement regarding the benign nevus components associated with CM was perfect (Cohen's Kappa: 1.0). PRAME was significantly more expressed in thick invasive CMs than in thin cases (p = 0.02). (4) Conclusions: PRAME IHC should be considered for the diagnostic evaluation of nevus-associated CM and is most useful in cases of thick melanomas. Pathologists should carefully consider that a PRAME-positive cellular population within the context of a nevus could indicate a CM associated with the nevus. A negative result does not rule out this possibility.

Tattoo-Associated Skin Reaction in a Melanoma Patient Receiving B-RAF and MEK Inhibitors: A Case Report with an Emphasis on Etiopathogenic and Histological Features.

Tattoo-associated cutaneous reactions have become quite frequent given the increasing percentage of tattooed subjects globally and also in Italy. On the other hand, the increasing use of target therapy is showing the ability of these drugs to affect the immune system and also cause adverse tattoo-related reactions. In this paper, we report a case of a 42-year-old patient with stage-IIID melanoma undergoing treatment with Dabrafenib and Trametinib. The patient reported erythema, oedema and scaling in areas of the body containing a black tattoo, and, conversely, no signs and/or symptoms in areas with tattoos of a different color. Histopathological and immunohistochemical features indicated a lympho-histiocytic reaction with a granulomatous morphology, mainly distributed around the vessels and hair adnexa. By discussing the cases reported in the literature prior to ours, we concluded and provided the possible indications of the pathogenesis.

LIGHT/TNFSF14 Affects Adipose Tissue Phenotype.

LIGHT/TNFSF14 is linked to several signaling pathways as a crucial member of a larger immunoregulatory network. It is primarily expressed in inflammatory effector cells, and high levels of LIGHT have been reported in obesity. Thus, with the aim of deepening the knowledge of the role of LIGHT on adipose tissue phenotype, we studied wild-type (WT), Tnfsf14-/-, Rag-/- and Rag-/Tnfsf14- (DKO) mice fed a normal diet (ND) or high-fat diet (HFD). Our results show that, although there is no significant weight gain between the mice with different genotypes, it is significant within each of them. We also detected an increase in visceral White Adipose Tissue (vWAT) weight in all mice fed HFD, together with the lowest levels of vWAT weight in Tnfsf14-/- and DKO mice fed ND with respect to the other strain. Inguinal WAT (iWAT) weight is significantly affected by genotype and HFD. The least amount of iWAT was detected in DKO mice fed ND. Histological analysis of vWAT showed that both the genotype and the diet significantly affect the adipocyte area, whereas the number is affected only by the genotype. In iWAT, the genotype and the diet significantly affect mean adipocyte area and number; interestingly, the area with the least adipocyte was detected in DKO mice fed ND, suggesting a potential browning effect due to the simultaneous lack of mature lymphocytes and LIGHT. Consistently, Uncoupling Protein 1 (UCP1) staining of iWAT demonstrated that few positive brown adipocytes appeared in DKO mice. Furthermore, LIGHT deficiency is associated with greater levels of UCP1, highlighting the lack of its expression in Rag-/- mice. Liver examination showed that all mice fed HFD had a steatotic liver, but it was particularly evident for DKO mice. In conclusion, our study demonstrates that the adipose tissue phenotype is affected by LIGHT levels but also much more by mature lymphocytes.

Macrophages and angiogenesis in human lymphomas.

A link exists between chronic inflammation and cancer and immune cells, angiogenesis, and tumor progression. In hematologic malignancies, tumor-associated macrophages (TAMs) are a significant part of the tumor microenvironment. Macrophages are classified into M1/classically activated and M2/alternatively activated. In tumors, TAMs are mainly constituted by M2 subtype, which promotes angiogenesis, lymphangiogenesis, repair, and remodeling, suppressing adaptive immunity, increasing tumor cell proliferation, drug resistance, histological malignancy, and poor clinical prognosis. The aim of our review article is to define the role of TAMs and their relationship with the angiogenesis in patients with lymphoma reporting both an analysis of main published data and those emerging from our studies. Finally, we have discussed the anti-angiogenic approach in the treatment of lymphomas.