Langerhans Cell Histiocytosis Patients Research Articles

Clinical features and treatment outcomes of liver involvement in paediatric Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is the most common histiocytic disorder in children, and liver involvement in LCH is rare. This retrospective study reported the clinical features and prognosis of patients with hepatic LCH. Liver involvement was defined by histopathological findings, liver dysfunction or abnormalities, or ultrasound imaging. A total of 130 patients (14.5%) with hepatic LCH out of 899 in the LCH population were enrolled. Patients with liver involvement had greater frequencies of skin, lung, hearing system, and haematologic system involvement, and hemophagocytic lymphohistiocytosis (P<0.001, 0.001, 0.002, 0.009, and <0.001, respectively). Overall survival and progression-free survival were lower in LCH patients with liver involvement than in those without liver involvement (P<0.001 and <0.001). In patients with liver involvement, the overall survival (OS) and progression-free survival (PFS) rates were lower in patients with cholangitis than in those without cholangitis (P<0.020 and 0.030). For the treatment response, the response rate of hepatic LCH patients to initial first-line therapy (n=89) was 22.5%. However, there was no significant difference in the response rate or recurrence rate between patients who shifted from first-line treatment to second-line treatment (n=29) or to targeted therapy (n=13) (P=0.453 and 1.000). The response rate of hepatic LCH patients who received initial second-line therapy (n=13) was 38.5%. Two of these patients subsequently experienced bone recurrence. The response rate of hepatic LCH patients who received initial targeted therapy (n=16) was 75.0%. Three patients subsequently experienced recurrence, including 2 in the bone and 1 in the liver and skin. A total of 39.3% of patients who received second-line treatment had severe myelosuppression (grade III-IV), and 50.8% had varying degrees of gastrointestinal events, whereas there was no severe toxicity in patients who received first-line treatment and targeted therapy. Four patients underwent liver transplantation because of liver cirrhosis. The patients’ liver disease improved within a follow-up period of 18-79 months. This study demonstrated that LCH with liver involvement, especially cholangitis, indicates a poor prognosis. Targeted therapy provides a good treatment response and less toxicity. However, it may relapse after withdrawal. Liver transplantation is still a reliable salvage option for patients with end-stage liver disease.

Exploration of treatment in childhood Langerhans cell histiocytosis based on inflammatory and malignant symptoms: a pilot study

BackgroundMultisystem childhood Langerhans cell histiocytosis (LCH) patients, especially those with risk organ (RO) involved, had not been satisfactorily treated under the international traditional schemes as high incidences of reactivation with late sequelae were largely reported. Over years, we have observed that LCH patients with varied clinical symptoms responded differently to different drugs, suggesting the current grouping strategies based only on the number of organs involved might be inadequate. LCH has been defined as an inflammatory myeloid tumor, thus this study has innovatively divided LCH pediatric patients into inflammatory or malignant symptoms group, and given different intensity treatment regimens to different groups.AimThis clinical study aimed to explore a more appropriate patient grouping system according to the LCH symptom presentations and examine the clinical outcomes of treatment strategies in different groups.MethodsAccording to the clinical manifestations, 37 cases of children were divided into Group A (only inflammatory symptoms) and Group B (malignant symptoms with or without inflammatory symptoms). Patients in Group A and B were initially treated with vindesine (VDS) and methylprednisolone (PSL), and VDS, PSL, pirarubicin (THP) and cyclophosphamide (CTX), respectively. Treatment responses were evaluated six weeks after the induction therapy in all patients, and the criteria were disease status and clinical scores of symptoms.ResultsPre- and post-treatment scores were 1.22 ± 0.547 and 0.00 ± 0.00 in Group A, and 14.79 ± 1.686 and 1.00 ± 1.563 in Group B, respectively. All patients had subsequentlly received maintenance therapy without progressive disease. The 4-year overall survival (OS) rate was 100% in both groups and the 4-year event-free survival (EFS) was 94.4% in Group A and 89.5% in Group B, respectively. There were no obvious adverse events (AE) in Group A, whereas the main AE in Group B were alopecia and non-lethal hematological toxicity.ConclusionStratification according to patients’ clinical symptoms, with low-intensity treatment for inflammatory symptoms (mild manifestations) and intensive treatment with multiple drugs for malignant symptoms (severe manifestations), is a positive exploration that simplifies stratification method, achieves good long-term remission of the disease, and obtains a higher survival rate and quality of life, which seemed to be more appropriate for LCH patients.

Langerhans Cell Histiocytosis With Unusual Hexagonal Crystals in Addition to Usual Charcot-Leyden Crystals. Report of a Patient With Possible Process of Crystal Formation and Clinical Significance of a "Necrotic" Change.

Langerhans cell histiocytosis is a rare neoplastic disorder characterized by the proliferation of Langerhans cells and often accompanied by eosinophil infiltration. Charcot-Leyden crystals, composed of galectin 10, are occasionally observed in Langerhans cell histiocytosis; however, histological images are rarely reported. We herein present a patient with Langerhans cell histiocytosis with Charcot-Leyden crystals and hexagonal crystals by describing the histologic and immunohistochemical features of a lymph node. A unique distribution of Charcot-Leyden crystals and hexagonal crystals was observed in this patient, shedding light on their possible formation process of the latter. We discuss the biological significance of eosinophilic abscesses in Langerhans cell histiocytosis and propose that these crystals may be linked to extracellular trap-cell death (ETosis). This example challenges the conventional characterization of "necrosis" in Langerhans cell histiocytosis and underscores the importance of recognizing ETosis as a potential mechanism involved in the pathogenesis of Langerhans cell histiocytosis. Further studies are underway to validate significance of these findings in a larger cohort of Langerhans cell histiocytosis patients.

The plasma-soluble CSF1R level is a promising prognostic indicator for pediatric Langerhans cell histiocytosis.

Langerhans cell histiocytosis (LCH) is a rare hematologic neoplasm characterized by the clonal proliferation of Langerhans-like cells. Colony-stimulating factor 1 receptor (CSF1R) is a membrane-bound receptor that is highly expressed in LCH cells and tumor-associated macrophages. In this study, a soluble form of CSF1R protein (sCSF1R) was identified by plasma proteome profiling, and its role in evaluating LCH prognosis was explored. We prospectively measured plasma sCSF1R levels in 104 LCH patients and 10 healthy children using ELISA. Plasma sCSF1R levels were greater in LCH patients than in healthy controls (p<.001) and significantly differed among the three disease extents, with the highest level in MS RO+ LCH patients (p<.001). Accordingly, immunofluorescence showed the highest level of membrane-bound CSF1R in MS RO+ patients. Furthermore, the plasma sCSF1R concentration at diagnosis could efficiently predict the prognosis of LCH patients treated with standard first-line treatment (AUC=0.782, p<.001). Notably, dynamic monitoring of sCSF1R levels could predict relapse early in patients receiving BRAF inhibitor treatment. In vitro drug sensitivity data showed that sCSF1R increased resistance to Ara-C in THP-1 cells expressing ectopic BRAF-V600E. Overall, the plasma sCSF1R level at diagnosis and during follow-up is of great clinical importance in pediatric LCH patients.

Abstract 2564: Circulating monocytes decrease significantly following disease-directed therapy and may reflect disease expansion in Langerhans cell histiocytosis

Abstract Introduction: Langerhans Cell Histiocytosis (LCH) is a rare disorder characterized by clonal hematopoietic cell expansion forming eosinophilic granulomas. Treatment approaches vary based on disease severity. Despite established therapies, assessing treatment response, particularly regarding peripheral blood monocytes, lacks comprehensive markers. Methods: We studied 76 LCH patients, collecting data on demographics, diagnostic methods, and treatment responses. Peripheral blood absolute monocyte counts were analyzed at key time points, including disease onset, progression, and post-therapy reinstatement, using statistical tests for comparison. Results: Analyzing data from 76 patients (average age: 38), we found diverse disease presentations, with common imaging modalities being CT (37), PET (29), and MRI (22). Complete responses were observed in 17 of 49 patients, with 11 undergoing local therapy. Conversely, 5 patients with pulmonary LCH and chronic tobacco use showed persistent progression. Notably, peripheral blood monocyte counts did not differ between initial and latest assessments, but on disease progression, the mean count (0.94 K/µL) significantly exceeded that following therapy reinstatement (0.31, p=0.000794). Results: Analyzing data from 76 patients (average age: 38), we found diverse disease presentations, with common imaging modalities being CT (37), PET (29), and MRI (22). Complete responses were observed in 17 of 49 patients, with 11 undergoing local therapy. Conversely, 5 patients with pulmonary LCH and chronic tobacco use showed persistent progression. Notably, peripheral blood monocyte counts did not differ between initial and latest assessments, but on disease progression, the mean count (0.94 K/µL) significantly exceeded that following therapy reinstatement (0.31, p=0.000794). Discussion: LCH is proposed to result from dysregulated hematopoiesis, leading to sequential somatic mutations during monocyte differentiation leading to clonal expansion of CD1A and CD207+ histiocytes. Our finding of increased monocyte count during disease progression may suggest elevated circulating LCH or heightened monocyte production for subsequent differentiation, potentially contributing to MHC Class 1 upregulation. This phenomena mirrors published findings from our own group in patients with Rosai Dorfman and Erdheim Chester Disease. To further elucidate the molecular underpinnings of LCH and explore the etiology of this monocyte trend, genetic sequencing analysis is in progress. Ultimately, monitoring peripheral blood monocyte dynamics could offer valuable insights into LCH progression and treatment response. Citation Format: Haadi Ali, Sam Reynolds, Sabrina Wilcox, Naina Chipalkatti, Asra Ahmed. Circulating monocytes decrease significantly following disease-directed therapy and may reflect disease expansion in Langerhans cell histiocytosis [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 2564.

The use of BRAF-inhibitors as monotherapy and in combination with cytosine arabinoside and 2-chloro-2’deoxyadenosine in pediatric patients with different forms of Langerhans cell histiocytosis

Background. Langerhans cell histiocytosis (LCH) is a rare disease that occurs due to abnormal proliferation and expansion of myeloid precursors. The occurrence of mutations in genes that encode key kinases of MAPK-signaling pathway leads to its pathological activation and has been shown the cause of disease. Mutations in BRAF and MAP2K1 genes are the most frequent among LCH patients. The effectiveness of BRAF-inhibitors in LCH patients has been shown in numerous studies.The purpose of the study – analyze the experience of BRAF-inhibitor vemurafenib administration as monotherapy and in combination with cytosine arabinoside (ARA-C) and 2-chloro-2'-deoxyadenosine (2-CdA) in pediatric patients with different forms of LCH.Materials and methods. Fifteen patients with various forms of LCH were enrolled in the study. BRAF mutations were detected in 14 patients, mutation in the MAP2K1 gene was detected in one case. Patients with “risk organ” (RO) involvement were included in the first group (n = 9). These patients received combined therapy with vemurafenib and ARA-C/2-CdA. Patients without RO involvement, included in group 2 (n = 6), received vemurafenib as monotherapy. The assessment of the response to the therapy in group 1 was carried out in accordance with the DAS scale, in group 2 in accordance with the RECIST v1.1. The toxicity assessment in both groups was carried out in accordance with the CTCAE v5.0.Results. All patients in group 1 achieved non-active disease status with a median of 35 (28–61) days. In group 2 partial response to vemurafenib was achieved in 5 cases. Relapse after targeted therapy termination was diagnosed in two patients. Photodermatitis was the most common side effect of targeted therapy.Conclusions. The use of vemurafenib was effective in both groups. There were no cases of grade III–IV toxicity according to CTCAE v5.0 associated with vemurafenib administration in this study. The combination of vemurafenib and ARA-C/2-CdA showed high efficacy and good tolerability in group 1. Two cases of disease relapse after targeted therapy cessation in group 2 show that the monotherapy approach does not always allow to achieve long-term remission in LCH patients.

The value of 18F-FDG PET/CT in Langerhans cell histiocytosis.

To investigate the value of 18F-FDG PET/CT in diagnosis and disease evaluation of Langerhans cell histiocytosis (LCH). A retrospective analysis of 31 patients with LCH confirmed by histopathology was performed. A systematic analysis of the PET/CT imaging manifestations of LCH was performed, recording patients who were treated and receiving PET/CT for efficacy evaluation. In addition, clinical and laboratory data of LCH patients were collected, and the correlation between these data and PET/CT metabolic parameters was initially investigated. Of the 31 patients, thirty had at least 1 PET/CT positive lesions (96.7%), and one had only skin damage without abnormalities on PET/CT. Of 31 patients, fifteen (48.4%) had single system (SS) disease (9 cases with a single site and 6 cases with multiple sites) and 16 (51.6%) had multisystem (MS) disease (6 low risk and 10 high risk cases). The incidence of LCH lesions in the bone, lymphatic system, pituitary gland, liver, soft tissue, thyroid gland, thymus, and lungs was 20 cases (64.5%), 12 cases (38.7%), 3 cases (9.7%), 2 cases (6.5%), 2 cases (6.5%), 1 case (3.2%), 1 case (3.2%), and 8 cases (25.8%), respectively. A total of 21 PET/CT follow-up scanning were performed in 13 patients receiving chemotherapy, with 13 (61.9%) partial metabolic remission (PMR), 6 (28.6%) progressive metabolic disease (PMD), and 2 (9.5%) stable metabolic disease (SMD), according to PET Response Evaluation Criteria in Solid Tumors (PRECIST) 1.0. Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and Lactic Dehydrogenase (LDH) were positively correlated with TTLG (total TLG) (R2 = 0.3256, 0.2409, 0.4205, P < 0.05). The Re-examine SUVmax is positively correlated with re-examine LDH (R2 = 0.7285, P < 0.05). 18F-FDG PET/CT is an effective way to diagnose and evaluate LCH. PET metabolic parameters were associated with laboratory inflammatory markers, suggesting that 18F-FDG PET/CT may be helpful in evaluating disease activity of LCH.

Clinicogenomic associations in patients with Langerhans cell histiocytosis: a cohort study

This article presents an analysis of genotype and phenotype correlations in a pediatric cohort with Langerhans cell histiocytosis (LCH). Approximately 60% of LCH patients carry BRAF V600E somatic point mutation. Numerous studies have demonstrated that the presence of this mutation is associated with a more severe course of the disease and a higher risk of relapse. Apart from BRAF V600E mutation, other mutations in genes involved in the RAS/RAF/MEK/ERK signaling pathway have been identified in LCH. Next generation sequencing of DNA with high coverage of target regions is considered an optimal approach to detect somatic mutations other than BRAF V600E. The identification of somatic driver mutations holds great potential for enhancing our understanding of the phenotypic heterogeneity of LCH and developing targeted therapeutic strategies. The study was approved by the Independent Ethics Committee and the Scientific Council of the Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology.

Bronchoalveolar cytokine profile differentiates Pulmonary Langerhans cell histiocytosis patients from other smoking-related interstitial lung diseases

BackgroundPulmonary Langerhans cell histiocytosis (PLCH) is a rare interstitial lung disease (ILD) associated with smoking, whose definitive diagnosis requires the exclusion of other forms of ILD and a compatible surgical lung biopsy. Bronchoalveolar lavage (BAL) is commonly proposed for the diagnosis of ILD, including PLCH, but the diagnostic value of this technique is limited. Here, we have analyzed the levels of a panel of cytokines and chemokines in BAL from PLCH patients, in order to identify a distinct immune profile to discriminate PLCH from other smoking related-ILD (SR-ILD), and comparing the results with idiopathic pulmonary fibrosis (IPF) as another disease in which smoking is considered a risk factor.MethodsBAL samples were collected from thirty-six patients with different ILD, including seven patients with PLCH, sixteen with SR-ILD and thirteen with IPF. Inflammatory profiles were analyzed using the Human Cytokine Membrane Antibody Array. Principal component analysis (PCA) was performed to reduce dimensionality and protein–protein interaction (PPI) network analysis using STRING 11.5 database were conducted. Finally, Random forest (RF) method was used to build a prediction model.ResultsWe have found significant differences (p < 0.05) on thirty-two cytokines/chemokines when comparing BAL from PLCH patients with at least one of the other ILD. Four main groups of similarly regulated cytokines were established, identifying distinct sets of markers for each cluster. Exploratory analysis using PCA (principal component analysis) showed clustering and separation of patients, with the two first components capturing 69.69% of the total variance. Levels of TARC/CCL17, leptin, oncostatin M (OSM) and IP-10/CXCL10 were associated with lung function parameters, showing positive correlation with FVC. Finally, random forest (RF) algorithm demonstrates that PLCH patients can be differentiated from the other ILDs based solely on inflammatory profile (accuracy 96.25%).ConclusionsOur results show that patients with PLCH exhibit a distinct BAL immune profile to SR-ILD and IPF. PCA analysis and RF model identify a specific immune profile useful for discriminating PLCH.

Deciphering the Epigenetic Landscape in Histiocytic Neoplasms

Background: Histiocytic neoplasms are driven by mutations activating the MAPK/ERK pathway; however, their epigenetic landscape remains poorly understood. MicroRNAs (miRNAs) are epigenetic regulators implicated in cancer development. Moreover, DNA methylation of miRNAs affects hematological malignancies development. Our previous study identified a unique miRNA expression signature in Erdheim-Chester Disease (ECD) patients. To further understand the biological mechanisms of ECD, we investigated the involvement of miRNAs, genes, and their methylation status in ECD, Langerhans cell histiocytosis (LCH), and Rosai-Dorfman disease (RDD). Methods: Methylation profiles of 14 LCH, 6 ECD, and 10 RDD patients were determined from histyocitic infiltrated tissues (Illumina EPIC-methylation array). These were compared to controls, suture granulomas (n=4), localized inflammatory reactions characterized by non-neoplastic histiocytic infiltrates. miRNAome data was identified by NanoString analysis and qRT-PCR. Results: We identified significant alterations in 23,322 methylation sites (FDR&amp;lt;0.05, |Δß|≧20%) between controls and the histiocytosis group, indicating differential epigenetic regulation. ECD and LCH exhibited a shared methylation signature distinct from RDD. Pathway analyses revealed that the differentially methylated genes (DMGs) were involved in inflammatory response, RAS, TNF, and PI3K-mTOR signaling pathways, linked to histiocytic neoplasms. Specifically, we found DMG involvement in regulation and generation of non-coding RNAs. Notably, we observed significant downregulation of the let7-miRNA family, particularly let7b, in ECD and LCH patients. Subsequent analysis revealed hypermethylation of specific CpG islands in the let7b DNA sequence, potentially silencing let7b expression in these diseases. Given the let7-miRNA family's role in regulating the MAPK pathway, this suggests a novel mechanism in the pathogenesis of these neoplasms. Conclusions: We provide valuable insights into differential methylation patterns in histiocytosis neoplasms, highlighting the involvement of epigenetic modifications in their development and progression. This enhances our understanding of histiocytosis development and may contribute to the identification of novel diagnostic and therapeutic approaches for these patients.

Adult Langerhans Cell Histiocytosis with Liver Involvement

Background Langerhans cell histiocytosis (LCH) is a rare, heterogeneous histiocytic disorder. We demonstrated liver involvement at baseline indicated poor survival in adult LCH in our previous study. Aims The aim of this study was to describe clinical features, liver biochemistry, radiology findings, genomic analyses, treatment approaches, and outcomes of adult LCH patients with liver involvement. Methods We conducted a retrospective analysis of all adult LCH patients (≥ 14 years) seen at Peking Union Medical College Hospital (Beijing, China) between January 2001 and December 2022. Liver involvement by one or more of the following: either hepatomegaly, defined as a liver edge greater than 3 cm below the costal margin at the mid clavicular line, or liver dysfunction defined either by abnormal serum biochemical tests including bilirubin greater than 1.5 times the upper limit of normal, alkaline phosphatase (ALP) greater than 1.5 times the upper limit of normal, γ-glutamyl transpeptidase (GGT) greater than 1.5 times the upper limit of normal; or histopathological findings of active disease. Results Among 451 newly diagnosed adult LCH patients, 93 patients had liver involvement at diagnosis and 22 patients had liver involvement at relapse were enrolled, including 80 males (69.6%), and the median age was 32 years (range, 15-66 years). 111 of 115 patients had full liver function test. 70 patients (63.1%) had elevated ALP; 96 patients (86.5%) had elevated GGT, and the median level was 157 U/L (range, 14-2249 U/L); 16 patients (14.4%) had elevated total bilirubin, and the median level was 12.5 umol/L (range, 1.7-248.1umol/L); Among 48 patients who had sufficient DNA for next-generation sequencing, BRAFV600E (20.8%), BRAFN486_P490 (37.5%) and MAP2K1(12.5%) were the most common alternations. In total, 99 patients (86.1%) received first-line systematic treatment, including 76 patients who received chemotherapies (methotrexate/cytarabine regimens, cytarabine monotherapy, vindesine/prednisone-based regimens, cladribine monotherapy and corticosteroid), 15 patients who received immunomodulatory drugs (IMiDs) therapies (thalidomide/cyclophosphamide/dexamethasone regimens and lenalidomide/dexamethasone regimens) and 8 patients who received target therapies (BRAF inhibitors and MEK inhibitors). After a median 39-month follow-up (range 1-168 months), thirteen patients died during follow-up. The estimated 3-year OS rate was 85.5%. 44 patients had disease progression. The median PFS duration was 31.4 months. Nine patients got cirrhosis during follow-up and 2 patients underwent liver transplantation. Univariate analysis was performed to evaluate the prognostic factors of OS and PFS. Patients with elevated total bilirubin at baseline had significantly shorter OS and PFS. Patients who had 3 or more abnormal serum live function tests (including ALT, AST, ALP, GGT, total bilirubin and ALB), and patients with elevated high sensitive C reactive protein (hsCRP) had significantly shorter PFS. Patients who received target therapy or iMIDs-based therapy had significantly longer PFS than patients who received other systemic treatments. In multivariable analyses, Patients who had 3 or more abnormal serum live function tests (HR 2.652, 95% CI 1.256-5.602), and treatment with iMIDs (HR 0.076, 95% CI 0.010-0.564) remained predictive factors for PFS. Conclusion Adult LCH patients with liver involvement most had elevated GGT and ALP. Elevated hsCRP and 3 or more abnormal live function tests predict poor outcomes. Target therapy or iMIDs-based therapy showed better outcomes.

Hematological Involvement in Childhood Langerhans Cell Histiocytosis: A Cohort Study of 303 Patients

Introduction: Hematological involvement (HI) is a life-threatening involvement of Langerhans cell histiocytosis (LCH). Since 1975, its definition is based on the Lahey criteria: Anemia (Hb &amp;lt;10 g/dL and &amp;lt;9 g/dL in infants) and/or thrombocytopenia (platelet count &amp;lt;100x10 9/l). Methods: Among 2,234 patients &amp;lt; 18 years enrolled in the French histiocytosis registry (cutoff date May 2023), 303 patients presented HI. We differentiated mild HI (MHI) (Hb &amp;gt; 7 g/dl and Platelets &amp;gt; 20x10 9/l) from severe HI (SHI) (Hb ≤ 7 g/dl and Platelets ≤ 20x10 9/l) by using usual cutoffs for transfusion requirements. Results: Median age at diagnosis was one year and sex was male in 49%. The median follow-up in the 258 survivors was 10.9 years, while death occurred after a median of 0.9 years in the 45 patients who died (Figure 1A). Only 3 patients died later than two years of initial diagnosis. The HI was mild in 150 cases and severe in 153 cases. BRAF v600E was found in 88 among the 101 patients for which mutation analysis was documented. Patients with SHI had significantly more lung involvement (35 % vs 19 %), more hepatic involvement (72 % vs 21 %), and more skin involvement (85 % vs 61 %). Morphological bone marrow infiltration by CD1a positive cells could not differentiate between SHI and MHI and bone marrow features were hardly informative. Signs of myelofibrosis were documented in 9 patients mostly later in the disease course. Lastly, 44 macrophage activation syndromes were observed exclusively in SHI. For 11 of those patients panel analyses of hemophagocytic lymphohistiocytosis genes did not show any bi-allelic pathogenic variants. 20 patients did not receive any therapy, including one with SHI and 19 with MHI. An intensive approach with hematologic stem cell transplantation (HSCT) (n=11) and 2-Cda-Cytarabine (2-Cda-AraC) (n=44) was proposed almost only for SHI. MAPK-inhibition was used in 40 patients. Three deaths were observed among the MHI and 42 among the SHI. From 1983 to 1998 mortality was about 50% and 30 of 63 patients died. With the establishment of the second-line treatment by 2-Cda-AraC mortality decreased drastically and from 1998 to 2014 only 13 of 194 patients died. From 2014 on patients received exclusively MAPK-inhibition as second line treatment and 2 of 46 patients died (one without therapy, one at the initiation). The overall survival is depicted in figure 1A. Neurodegenerative (ND) complications were observed in 32 patients (10.5%) with a median delay of 4.8 years after initial LCH diagnosis and incidence of ND was independent of the MHI or SHI group (Figure 1B). Conclusion: In Langerhans cell histiocytosis, the classic definition of hematological involvement by the Lahey criteria should be reconsidered. HI may be limited to severe HI that included almost all medical complications and warrants innovative approaches, while mild HI can be managed by the classic therapeutical approach. Even if progress has been achieved in the treatment of LCH patients with HI with more than 95% achieving short-term control, long term neurodegeneration remains a challenge in this group of patients, which warrants further research. Figure 1: A) Kaplan-Meier curve of cumulative incidence of death for all the 303 patients, regardless of therapy. B) Risk of clinical neurodegenerative symptoms in the same cohort (considering death as a censor).

First Blood: Pre-Therapy BRAFV600E+ PBMC Identifies a Novel Clinical Risk Category for Patients with LCH

Purpose: Langerhans Cell Histiocytosis (LCH) is a myeloproliferative neoplasia driven by somatic mutations in the mitogen-activated protein kinases pathway (MAPK). LCH has historically been clinically staged as “high risk” (e.g. liver, spleen and/or bone marrow involvement, HR) or “low risk” (LR) due relative to risk of death in earlier trials. However, clinical staging is complicated by different sensitivities of imaging and, more recently, molecular analyses. We previously identified that BRAFV600E allele in peripheral blood mononuclear cells (PBMC) in patients with HR LCH, which supported a model of LCH arising from hematopoietic myeloid precursors. To determine the clinical significance of somatic lesion BRAFV600E mutations as well as ability to detect pre-therapy BRAFV600E+ PBMC at diagnosis, we analyzed an extended cohort of LCH patients with longitudinal clinical evaluations. Methods: Genomic DNA was isolated from 366 lesion biopsies and the PBMCs of 294 patients with active LCH before initial therapy. The percentage of PBMC with the BRAFV600E allele in patients was determined by quantitative polymerase chain reaction. Lesion genotype and ability to detect pre-therapy BRAFV600E in PBMC were correlated with clinical features including i) clinical risk status, ii) extent of disease (single lesion vs multifocal; single system vs multisystem), iii) response to therapy, v) and time to relapse were analyzed using a chi-square test. Fluorescence-activated cell sorting (FACS), DNA amplification and subsequent qPCR was performed on 15 pretherapy BRAFV600E+ blood samples to explore the relationship between different myeloid lineages (CD3, CD19, CD56, CD14, CD16, CD11c) and extent of LCH disease. Survival proportions were calculated using the Kaplan-Meier (product limit) method and a log-rank (Mantel-Cox) test was used to calculate the significance of the difference between survival curves. Results: Median age was 3.01 years (range 3.6 days to 21.5 years), 58.5% of the patients were male (41.5% female), and 15.4% had HR disease (84.6% LR). Among patients with LR disease, 33.0% had multisystem, 23.1% had multi-focal single system, and 44.0% had single lesions. Lesion genotypes were 51.9% BRAFV600E and 49.1% not BRAFV600E. BRAFV600E in LCH lesions was associated with lower age at diagnosis and higher prevalence of HR disease. However, after a median follow-up time of 1.6 years (range 1 month to 8.5 years) there was no difference in EFS between BRAFV600E and alternative mutations (p=0.35). Notably, for the entire cohort, presence of BRAFV600E in diagnostic PBMC was highly associated with younger patients, clinical HR disease and risk of developing LCH-associated neurodegeneration (LCH-ND). For patients with BRAFV600E+ lesions, 32.5% had detectable BRAF V600E in pre-therapy PBMC: 100% of HR, 52.6% of multisystem LR, 18.4% of multi-focal single system LR and 0% of single lesion. Further, after a median follow-up time of 2.0 years (range 1 month to 9,1 years) clinical LR PBMC BRAFV600E+ represented a group at higher risk of treatment failure compared to BRAFV600E-neg LR (p=0.01). BRAFV600E alleles were present in PBMC at diagnosis in all of the sorted myeloid populations, with consistent enrichment in myeloid dendritic cells and monocytes. There was no significant correlation between BRAFV600E allele burden (percentage of BRAFV600E+ PBMC) and clinical risk, and no significant differences in the distribution of allele burden within lineages. Conclusion: Ability to detect pretherapy BRAFV600E+ represents an important clinical biomarker for patients with LCH. Results from this study support the potential for pre-therapy PBMC BRAFV600E to predict clinical risks, inform pathogenic mechanisms in LCH, and identify LR PBMC BRAFV600E+ as a novel clinical risk group. We hypothesize that persistence of hematopoietic clones and circulating myeloid precursors may underlie the increased risks of treatment failure and development of LCH-ND in patients previously presumed to have “low risk” disease.

Immune microenvironment associated with the severity of Langerhans cell histiocytosis in children

The aim of this study is to investigate the clinical potential of immune microenvironment in peripheral blood for the severity and therapeutic efficacy of Langerhans cell histiocytosis (LCH). A total of 200 newly diagnosed children with LCH during 10 years was enrolled for analysis in this study. Peripheral blood samples were acquired from patients before treatment in our hospital and immune indicators were detected by a four-color flow cytometer. The levels of CD3 + CD8 + T cell, CD3 + CD4 + HLA-DR + T cell, CD3 + CD8 + HLA-DR + T cell, IL-4, IL-6, IL-10 and IFN-γ in peripheral blood were markedly elevated in LCH patients vs. healthy controls. Patients with multiple system with risk organ involvement (MS-RO + ) exhibited higher levels in IL-6, IL-10 and IFN-γ, CD3 + CD4 + HLA-DR + T cell and CD3 + CD8 + HLA-DR + T cell, compared to those in patients without risk organ involvement (RO-). Patients who responded effectively to initial chemotherapy showed significantly lower levels of IL-4, IL-10, IFN-γ, CD3 + CD4 + HLA-DR + T cell and CD3 + CD8 + HLA-DR + T cell in peripheral blood, compared to those in patients who did not respond to initial chemotherapy. Furthermore, univariate analyses were performed that the higher levels of CD3 + CD4 + HLA-DR + T cells, CD3 + CD8 + HLA-DR + T cells and IL-10 in peripheral blood were related to non-response in LCH after initial chemotherapy. Immune microenvironment in peripheral blood may be associated with the severity and treatment response of LCH. The levels of CD3 + CD4 + HLA-DR + T cells, CD3 + CD8 + HLA-DR + T cells and IL-10 may be biomarkers to predict treatment response of LCH patients.

Somatic ARAF mutations in pediatric Langerhans cell histiocytosis: clinicopathologic, genetic and functional profiling.

ARAF mutations have been identified in a limited subset of patients with Langerhans cell histiocytosis (LCH), a rare disorder characterized by abnormal proliferation of Langerhans cells. LCH is primarily instigated by mutations in the mitogen-activated protein kinase (MAPK) signaling pathway, with BRAFV600E and MAP2K1 mutations constituting most cases. ARAF mutations in LCH highlight the heterogeneity of the disease and provide insights into its underlying molecular mechanisms. However, the occurrence of ARAF-positive LCH cases is extremely rare, with only two reported globally. Although they may be linked to a more aggressive form of LCH and a more severe clinical progression, the clinical significance and functional consequences of these mutations remain uncertain. We performed next-generation sequencing (NGS) to explore driver mutations in 148 pediatric LCH patients and recognized a series of mutations, including an identical novel somatic ARAF mutation, c.1046_1051delAGGCTT (p.Q349_F351delinsL), in four pediatric LCH patients. It was considered an ARAF hotspot mutation. All reported ARAF-positive patients worldwide exhibited characteristic pathological features of LCH, albeit with involvement across multiple systems. In vitro functional studies showed that this mutation could trigger the MAPKinase pathway and phosphorylate its downstream effectors MEK1/2 and ERK1/2 (relatively weaker than BRAFV600E). Over-activation of mutant A-Raf kinase could be inhibited by the BRAF inhibitor vemurafenib. LCH is uncommon, and ARAF mutation is even rarer. In our study, we have identified a novel hotspot somatic ARAF mutation, which has been verified through functional analysis to be an activating mutation. LCH patients with ARAF mutation typically have an unfavorable prognosis due to limited treatment experiences, although they do not exhibit a high relapse rate. To aid in the development of personalized treatment approaches and prognostic markers for LCH patients, it is recommended to conduct typical pathological and immunohistochemical examinations, as well as genetic tests utilizing a targeted gene panel or whole exome sequencing (WES), for LCH diagnosis, thereby promoting the use of inhibitor treatment strategies.

Serum levels of soluble interleukin 2 receptor (sIL-2R), tumor necrosis factor-alpha (TNF-α), and immunoglobulin M are correlated with the disease extent in childhood Langerhans cell histiocytosis.

This study aimed to identify peripheral parameters associated with the severity of Langerhans cell histiocytosis (LCH) and to look for indicators associated with improvement in LCH patients with risk-organ involvement. This study enrolled LCH patients who were assessed as active disease-better (AD-B) after treatment. Patients were divided into the single system (SS) group, multisystem disease without risk-organ involvement (RO- MS) group, and multisystem disease with risk-organ involvement (RO + MS) group. Serum cytokines, immunoglobulins, and lymphocyte subsets were measured at admission for all three groups. Changes in these indicators after treatment were also analyzed. From January 2015 to January 2022, a total of 46 patients were recruited in the present study, including 19 patients (41.3%) in the SS group, 16 patients (34.8%) in the RO- MS group, and 11 patients (23.9%) in the RO + MS group. Serum levels of soluble interleukin 2 receptor (sIL-2R) (> 912.5 U/mL), tumor necrosis factor-alpha (TNF-α) (> 20.3pg/mL), and immunoglobulin M (< 1.12g/L) were found to be effective in identifying patients in the RO + MS group. Furthermore, the levels of sIL-2R (SS vs RO + MS: P = 0.002, RO- MS vs RO + MS: P = 0.018) and CD8 + T-cell count (SS vs RO + MS: P = 0.028) significantly declined in the RO + MS group after treatment, indicating disease improvement. The levels of sIL-2R and TNF-α were positively correlated with the extent of disease, while the levels of IgM were negatively correlated with the extent of disease. Additionally, the levels of sIL-2R and CD8 + T-cell count could serve as useful indicators to evaluate the treatment response in RO + MS-LCH patients.

Imaging Phenotypes and Evolution of Hepatic Langerhans Cell Histiocytosis on CT/MRI: A Retrospective Study of Clinical Cases and Literature Review.

(1) Background: pathological changes in hepatic Langerhans cell histiocytosis (LCH) have been observed; however, corresponding imaging findings can appear vague to physicians and radiologists. The present study aimed to comprehensively illustrate the imaging findings of hepatic LCH and to investigate the evolution of LCH-associated lesions. (2) Methods: LCH patients with liver involvement treated at our institution were retrospectively reviewed along with prior studies in PubMed. Initial and follow-up computed tomography (CT) and magnetic resonance imaging (MRI) were systematically reviewed, and three imaging phenotypes were created based on the lesion distribution pattern. Clinical features and prognoses were compared among the three phenotypes. Liver fibrosis was evaluated visually on T2-weighted imaging (T2WI) and diffusion-weighted imaging (DWI), and apparent diffusion coefficient (ADC) values of the fibrotic areas were measured. Descriptive statistics and a comparative analysis were used to analyze the data. (3) Results: based on the lesion distribution pattern on CT/MRI scans, patients with liver involvement were categorized as the disseminated lesion phenotype, scattered lesion phenotype, and central periportal lesion phenotype. Patients with scattered lesion phenotype were typically adults, and only a few of them had hepatomegaly (npresent = 1, 1/6, 16.7%) and liver biochemical abnormalities (npresent = 2, 2/6, 33.3%); patients with central periportal lesion phenotype were typically young children, and hepatomegaly and biochemical abnormalities were more apparent in these patients than those with another phenotype; and those with the disseminated lesion phenotype were found in all age groups, and the lesions evolved rapidly on medical imaging. Follow-up MRI scans show more details and can better document the evolution of lesions than CT. T2-hypointense fibrotic changes, including the periportal halo sign (npresent = 2, 2/9, 22.2%), patchy liver parenchyma changes (npresent = 6, 6/9, 66.7%), and giant hepatic nodules close to the central portal vein (npresent = 1, 1/9, 11.1%), were found, while fibrotic changes were not observed in patients with the scattered lesion phenotype. The mean ADC value for the area of liver fibrosis in each patient was lower than the optimal cutoff for significant fibrosis (METAVIR Fibrosis Stage ≥ 2) in a previous study that assessed liver fibrosis in chronic viral hepatitis. (4) Conclusions: The infiltrative lesions and liver fibrosis of hepatic LCH can be well characterized on MRI scans with DWI. The evolution of these lesions was well demonstrated on follow-up MRI scans.

Comparison of neuroimaging features of histiocytic neoplasms with central nervous system involvement: a retrospective study of 121 adult patients

ObjectivesTo compare neuroimaging characteristics of three types of histiocytoses, namely Langerhans cell histiocytosis (LCH), Erdheim-Chester disease (ECD), and Rosai-Dorfman disease (RDD), with central nervous system (CNS) involvement.MethodsA total of 121 adult patients with histiocytoses (77 LCH, 37 ECD, and 7 RDD) and CNS involvement were retrospectively included. Histiocytoses were diagnosed based on histopathological findings combined with suggestive clinical and imaging features. Brain and dedicated pituitary MRIs were systematically analyzed for tumorous, vascular, degenerative lesions, sinus, and orbital involvement and for hypothalamic pituitary axis involvement.ResultsEndocrine disorders, including diabetes insipidus and central hypogonadism, were more common in LCH patients than in ECD and RDD patients (p < 0.001). In LCH, tumorous lesions were mostly solitary (85.7%), located in the hypothalamic pituitary region (92.9%), and without peritumoral edema (92.9%), while in ECD and RDD, tumorous lesions were often multiple (ECD: 81.3%, RDD: 85.7%), their distribution was more widespread with meninges mostly involved (ECD: 75%, RDD: 71.4%), and they most likely presented with peritumoral edema (ECD: 50%, RDD: 57.1%; all p ≤ 0.020). Vascular involvement was an exclusive imaging characteristic of ECD (17.2%), which was not observed in LCH or RDD; this was also associated with a higher risk of death (p = 0.013, hazard ratio = 11.09).ConclusionThe typical characteristic of adult CNS-LCH was endocrine disorders with radiological findings limited to the hypothalamic pituitary axis. The pattern of multiple tumorous lesions with predominant involvement of meninges was the main manifestation of CNS-ECD and CNS-RDD, while vascular involvement was pathognomonic for ECD and associated with poor prognosis.Clinical relevance statementInvolvement of the hypothalamic-pituitary axis is the typical imaging characteristic of Langerhans cell histiocytosis. Multiple tumorous lesions, predominantly involving but not limited to meninges, occur in most Erdheim-Chester disease and Rosai-Dorfman disease patients. Vascular involvement occurs only in Erdheim-Chester disease patients.Key Points• The different distribution patterns of brain tumorous lesions can help differentiate among LCH, ECD, and RDD.• Vascular involvement was an exclusive imaging finding of ECD and was associated with high mortality.• Some cases with atypical imaging manifestations were reported to further expand the knowledge on these diseases.

Myeloid cells from Langerhans cell histiocytosis patients exhibit increased vesicle trafficking and an altered secretome capable of activating NK cells.

Langerhans cell histiocytosis (LCH) is a potentially life-threatening inflammatory myeloid neoplasia linked to pediatric neurodegeneration, whereby transformed LCH cells form agglomerated lesions in various organs. Although MAP-kinase pathway mutations have been identified in LCH cells, the functional consequences of these mutations and the mechanisms that cause the pathogenic behavior of LCH cells are not well understood. In our study, we used an in vitro differentiation system and RNA-sequencing to compare monocyte-derived dendritic cells from LCH patients to those derived from healthy controls or patients with Crohn's disease, a non-histiocytic inflammatory disease. We observed that interferon-γ treatment exacerbated intrinsic differences between LCH patient and control cells, including strikingly increased endo- and exocytosis gene activity in LCH patients. We validated these transcriptional patterns in lesions and functionally confirmed that LCH cells exhibited increased endo- and exocytosis. Furthermore, RNA-sequencing of extracellular vesicles revealed the enrichment of pathological transcripts involved in cell adhesion, MAP-kinase pathway, vesicle trafficking and T-cell activation in LCH patients. Thus, we tested the effect of the LCH secretome on lymphocyte activity and found significant activation of NK cells. These findings implicate extracellular vesicles in the pathology of LCH for the first time, in line with their established roles in the formation of various other tumor niches. Thus, we describe novel traits of LCH patient cells and suggest a pathogenic mechanism of potential therapeutic and diagnostic importance.

Detection of Immune Microenvironment Changes and Immune-Related Regulators in Langerhans Cell Histiocytosis Bone Metastasis.

The inflammation/immune response pathway is considered a key contributor to the development of Langerhans cell histiocytosis (LCH) bone metastasis. However, the dynamic changes in the immune microenvironment of LCH bone metastasis and critical regulators are still unclear. Expression profiling by arrays of GSE16395, GSE35340, and GSE122476 was applied to detect the immune microenvironment changes in the development of LCH bone metastasis. The single-cell high-throughput sequencing of GSE133704, involved in LCH bone lesions, was analyzed. The online database Metascape and gene set variation analysis (GSVA) algorithms were used to detect the gene function of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). The protein-protein interaction (PPI) network of hub regulators was constructed by the STRING database. In these results, key immune cells, such as Tem cells, NK T cells, CD8(+) T cells, and Th1 cells, were identified in LCH bone metastasis. These genes, which include LAG3, TSPAN5, LPAR5, VEGFA, CXCL16, CD74, and MARCKS, may significantly correlate with the cellular infiltration of B cells, aDCs, pDCs, cytotoxic cells, T cells, CD8+ T cells, T helper cells, and Tcm cells. In conclusion, our study constructed an atlas of the immune microenvironment of LCH bone metastasis. Genes including LAG3, TSPAN5, LPAR5, VEGFA, CXCL16, CD74, and MARCKS may be involved in the development of LCH bone metastasis. The hub gene-immune cell interactive map may be a potential prognostic biomarker for the progression of LCH bone metastasis and synergetic targets for immunotherapy in LCH patients.