Langerhans Cell Histiocytosis Patients Research Articles

Spectrum of Second Primary Malignancies in Pediatric and Adult Langerhans Cell Histiocytosis Cases

Introduction: Langerhans cell histiocytosis (LCH) is a rare MAPK-ERK pathway driven histiocytic neoplasm that occurs in pediatric as well as adult population. Despite improvement in clinical outcomes, there is some data to suggest an increased propensity to develop second primary malignancies (SPMs) in LCH patients. However, population-based studies analyzing the incidence and spectrum of SPMs in pediatric and adult LCH patients are lacking. In this study, we utilized the Surveillance, Epidemiology and End Results (SEER) database to examine the various SPMs occurring among pediatric and adult LCH cases. Methods: We used the November 2018 submission of the SEER 18 registry, which covers ~27.8% of the US population based on the 2010 census, as our database. We used the SEER*Stat version 8.3.6 statistical software to analyze data. We identified cases diagnosed with LCH as their first primary malignancy between 2000 and 2016 using International Classification of Diseases for Oncology edition 3 (ICD-O-3) codes, including LCH NOS (not otherwise specified) (9751/1), LCH (9751/3), LCH, unifocal (9752/1), LCH, multifocal (9753/3), LCH, disseminated, borderline (9754/1) and Disseminated LCH (9754/3). These cases were followed for 180+months, and the standardized incidence ratio (SIR) or relative risk and absolute excess risk (AER) were calculated. We examined the differences in occurrence of SPMs among the pediatric (Age <18 years) and adult population (Age ≥18 years). Additionally, we evaluated the concurrent and prior cancers in LCH patients as an exploratory objective. Results: The study included 1392 cases with LCH (Table 1), with median age at diagnosis 8 years (range newborn - 86 years). Out of these cases, 1205 (87%) were diagnosed as LCH and 186 (13%) as disseminated LCH. 936 cases (67%) were diagnosed at age <18 years (pediatric LCH), while 456 cases (33%) were diagnosed at age ≥18 years (adult LCH). The overall age-adjusted incidence rate for LCH was found to be 1 per 1,000,000. The incidence rate was 2.6 per 1,000,000 in pediatric LCH group and 0.4 per 1,000,000 in the adult LCH group. Out of the entire cohort, 20 (1.4%) cases developed a total of 21 SPMs [SIR 2.07; 95% Confidence Interval (CI): 1.28-3.16]. Median latency period to development of SPMs was 28 months. The pediatric LCH group had an overall higher risk of developing SPMs [SIR 6.42, 95%CI 2.08-14.97] than the general population, especially for hematologic malignancies [SIR 18.76, 95%CI 6.09-43.78], mainly, nodal Hodgkin lymphoma [SIR 60.93, 95%CI 7.38-220.12] and extranodal non-Hodgkin lymphoma [SIR 60.88, 95%CI 1.54-339.2]. No solid tumors were seen in this group. The adult LCH group did not have an overall increased risk of developing SPMs than the general population [SIR 1.71, 95%CI 0.98-2.77], except for Acute Lymphocytic Leukemia (ALL) [SIR 66.29, 95%CI 1.68-369.36] especially 60-119 months from diagnosis of LCH and miscellaneous cancers [SIR 11.43, 95%CI 2.36-33.39] especially 12-59 months after diagnosis of LCH. 62.5% of SPMs that developed in the adult LCH group were solid tumors, however, the overall risk for developing solid tumors was not higher than the general population [SIR 1.2, 95%CI 0.58-2.2], except for carcinoma in-situ of vulva [SIR 62.72, 95%CI 1.59-349.45] 2-11 months from diagnosis of LCH. Overall, tumors of the respiratory system (21%), female breast (13%) and prostate (9%) were the most common malignancies occurring prior to development of LCH whereas tumors of the respiratory system (28%), non-Hodgkin lymphoma (20%) and endocrine system (13%) occurred concurrent to LCH. Conclusion: To our knowledge, this is the first comprehensive population-based study assessing the incidence of SPMs in pediatric and adult LCH. Our study shows that the incidence of LCH is higher in the pediatric age group compared to adults. We found an increased risk for hematologic malignancies, specifically for Hodgkin and non-Hodgkin lymphoma in pediatric LCH compared to the general population. Among adult LCH, however, the risk was higher for development of ALL and carcinoma in-situ of vulva when compared to the general population. Our results may help guide survivorship and surveillance strategies among LCH patients. More studies are needed to understand the molecular underpinning leading to increased SPM formation in LCH patients. Disclosures No relevant conflicts of interest to declare.

Treatment Outcome and Prognostic Factors for Adult Langerhans Cell Histiocytosis

Background: The clinical features and prognosis of adult Langerhans cell histiocytosis (LCH) remained poorly defined. Although recurrent somatic activating mutations of BRAFV600E and additional genetic drivers of MAPK pathway had been discovered in LCH, most genomic analyses were from children and the spectrum of genetic alterations and the impact of these genetic mutations on clinical presentation in adult LCH remains elusive. To address these questions, we retrospectively studied the clinical features, organ involvement, treatment approaches, genomic analyses and outcomes of adult LCH patients in our center. Methods: Patients diagnosed with LCH between January 2001 and June 2020 at Peking Union Medical College Hospital were included in this retrospective study. BRAF or MAP2K1 mutation was detected by a custom-designed NGS panel. Patients were classified according to the number of systems involved: SS-s, one lesion in a single system; SS-m, multiple lesions within one single system; and MS, multiple systems involved. The overall survival (OS) was defined as the duration from the diagnosis of LCH to the date of death. The event free survival (EFS) was defined as the duration from the initiation of treatment for LCH to reactivation after treatment and death from any cause. Results: Overall 266 patients were enrolled, 177 patients were male (66.5%). The median age at diagnosis was 32 years (range, 18-79 years). At the time of diagnosis, 58 patients had SS-s LCH (21.8%), 26 patients had SS-m LCH with bone involvement (9.8%) and 182 patients had MS LCH (68.4%). The most common organ involved in MS patients was bone (69.8%), followed by the pituitary (61.5%), lung (61.0%), lymph nodes (35.2%), skin (26.4%), liver (23.1%), thyroid (13.7%), spleen (8.2%), CNS (3.8%) and gastrointestinal tract (1.1%). No patients had hematopoietic system involvement. For 67 patients, BRAF and MAP2K1 mutation status were successfully determined with NGS. BRAFV600E was detected in 26 patients (38.8%), BRAFV600D was detected in 1 patient (1.5%), BRAFT599I in 1 patient (1.5%) and BRAFdeletion mutation in 17 patients (25.4%), including 15 BRAF N486_P490 and 2 BRAF N486_P491delinsS. MAP2K1 mutation was detected in 13 patients (19.4%). BRAF status was related to disease features and extent of disease. BRAF deletion was found in 38.5% of patients with MS LCH, 7.1% of patients with SS LCH (P= 0.004). BRAF deletion was apparent in 69.2% of patients with liver involvement (P <0.001). While bone involvement was associated with BRAFV600E mutation (46.2% vs 13.2%, P = 0.033). The initial treatment of the whole cohort is illustrated in the flow diagram of Figure 1. The estimated 4-year OS and EFS of patients with SS-s LCH were 97.2% and 57.0%, respectively. Totally 201 MS or SS-m patients received first-line treatment at our hospital. After a median 43-month follow-up (range 1-214 months), 92 patients had reactivation. The median EFS was 38.5 months (95% CI, 20.9-56.1 months). To evaluate the prognostic factors of EFS using multivariate Cox regression model, the involvement of liver (HR 0.545, 95% CI 0.335-0.885) or spleen (HR 0.416, 95% CI 0.205-0.844) at baseline were predictive of poor EFS, while receiving cytarabine-based therapy as a first-line treatment (HR 2.195, 95% CI 1.441-3.344) and age older than 30 years at diagnosis (HR 1.660, 95% CI 1.087-2.533) predicted favorable EFS. BRAF or MAP2K1 mutation status did not significantly affect EFS. Seventeen patients died during follow-up. The estimated 4-year OS was 94.4% of patients with MS or SS-m. Conclusion: We first found more than 25% of adult LCH patients carried BRAFdeletion (BRAF N486_P490 or BRAF N486_P491delinsS), which was related with MS and liver involvement. Also, we demonstrated that liver and spleen involvement indicates a worse prognosis in adult LCH, age older than 30 years at diagnosis predicted favorable EFS and a cytarabine-based regimen should be considered as a first-line treatment for adult MS or SS-m LCH patients. Disclosures No relevant conflicts of interest to declare.

Patients with both Langerhans cell histiocytosis and Crohn's disease highlight a common role of interleukin-23.

AimTo present the first case series of patients with Langerhans cell histiocytosis (LCH) also affected by Crohn's disease (CD), both of which are granulomatous diseases, and in LCH investigate the role of interleukin (IL)‐23, which is a well‐described disease mediator in CD.MethodsA case series of three patients with LCH and CD were described; a cohort of LCH patients (n = 55) as well as controls (n = 55) were analysed for circulating IL‐23 levels; and the relation between the percentage of LCH cells in lesions and circulating IL‐23 levels was analysed in seven LCH patients.ResultsDifferential diagnostic challenges for these two granulomatous diseases were highlighted in the case series, and it took up to 3 years to diagnose CD. Elevated IL‐23 levels were found in LCH patients. The amount of lesional LCH cells correlated with the levels of circulating IL‐23.ConclusionBoth CD and LCH should be considered in patients with inflammatory gastrointestinal involvement. The IL‐23 pathway is a common immunological trait between these two granulomatous diseases.

Combination of Neoadjuvant Therapy and Liver Transplantation in Pediatric Multisystem Langerhans Cell Histiocytosis With Liver Involvement.

Background: Langerhans cell histiocytosis (LCH) is characterized by misguided myeloid differentiation, whose prognosis was poor with involvement of risk organs. Remaining issues include how to improve the outcomes of patients with risk-organ involvement.Methods: A retrospective study was conducted in Renji Hospital exploring the effects of neoadjuvant therapy in combination with pediatric liver transplantation (LT) for LCH patients based on data collected between October 2006 and October 2019.Results: We presented here five cases of multisystem LCH patients underwent systemic chemotherapy to control active lesions, followed by LT to treat end-stage liver diseases. Manifestations before LT included elevated transaminase levels (n = 5, 100%), jaundice (n = 4, 80%), ascites (n = 3, 60%), and variceal hemorrhage (n = 1, 20%). Three patients underwent orthotopic liver transplantation (OLT) and two underwent living donor liver transplantation (LDLT). Until December 2019, median follow-up time was 32 months (range, 2–67 months). Liver functions significantly improved compared with pre-operative conditions. One patient had perioperative hepatic artery complications and one patient had a recurrence in the lung. EBV infection occurred in four (80%) patients and CMV infection occurred in one (20%). There was one case of drug-induced liver injury diagnosed on biopsy 13 months after LT. None underwent re-transplantation and there were no rejection or portal vein and biliary complications.Conclusion: Combination of neoadjuvant therapy and LT is an effective paradigm in treatment of multisystem LCH with severe liver dysfunction. With advances in chemotherapy regimen for multisystem LCH and LT surgery, perspectives on prognosis for LCH children are promising.

Clinical presentation and prognostic analysis of adult patients with Langerhans cell histiocytosis with pulmonary involvement

BackgroundThe study aimed to investigate the clinical features and prognosis factors of adult patients with Langerhans cell histiocytosis (LCH) with pulmonary involvement, especially multisystem (MS) LCH with pulmonary involvement.MethodsWe retrospectively analyzed the demographic materials, clinical features and treatment outcomes of 119 adult LCH patients with pulmonary involvement at our center from January 1990 to November 2019.ResultsAmong 119 patients, 13 (10.9%) had single-system (SS) LCH, and 106 (89.1%) had MS-LCH with pulmonary involvement. SS-LCH patients had higher smoking rate (84.6% vs 52.8%, P = 0.026) and smoking index (300 vs 200, P = 0.019) than MS-LCH patients. The percentage of respiratory symptoms of SS-LCH patients was higher than MS-LCH patients (84.6% vs 53.8%, P = 0.034). Pulmonary function was impaired in 83.8% of the patients, and DLCO was the parameter most frequently impaired, accounting for 81.1%. The median DLCO was 65.1% predicted. Patients with pneumothorax had significantly worse DLCO (P = 0.022), FEV1 (P = 0.000) and FEV1/FVC (P = 0.000) than those without pneumothorax. During the follow-up, 72.4% of the patients had stable pulmonary function, and 13.8% showed improvements after chemotherapy. The estimated 3-year OS and EFS were 89.7 and 58.3%, respectively. Patients with a baseline FEV1 ≤ 55% predicted had worse OS. A history of pneumothorax indicated worse EFS and cytarabine based therapy predicted better EFS.ConclusionsAn FEV1 ≤ 55% predicted and a history of pneumothorax at diagnosis indicated a poor prognosis. Cytarabine based regimen may arrest the decline in pulmonary function in LCH patients with pulmonary involvement and improve EFS.

Endocrine Outcomes In Central Diabetes Insipidus: the Predictive Value of Neuroimaging "Mismatch Pattern".

The etiology of central diabetes insipidus (CDI) in children is often unknown. Clinical and radiological features at disease onset do not allow discrimination between idiopathic forms and other conditions or to predict anterior pituitary dysfunction. To evaluate the evolution of pituitary stalk (PS) thickening and the pattern of contrast-enhancement in relation with etiological diagnosis and pituitary function. We enrolled 39 children with CDI, 29 idiopathic and 10 with Langerhans cell histiocytosis (LCH). Brain magnetic resonance images taken at admission and during follow-up (332 studies) were examined, focusing on PS thickness, contrast-enhancement pattern, and pituitary gland size; T2-DRIVE and postcontrast T1-weighted images were analyzed. Seventeen of 29 patients (58.6%) with idiopathic CDI displayed "mismatch pattern," consisting in a discrepancy between PS thickness in T2-DRIVE and postcontrast T1-weighted images; neuroimaging findings became stable after its appearance, while "mismatch" appeared in LCH patients after chemotherapy. Patients with larger PS displayed mismatch more frequently (P = 0.003); in these patients, reduction of proximal and middle PS size was documented over time (P = 0.045 and P = 0.006). The pituitary gland was smaller in patients with mismatch (P < 0.0001). Patients with mismatch presented more frequently with at least one pituitary hormone defect, more often growth hormone deficiency (P = 0.033). The PS mismatch pattern characterizes patients with CDI, reduced pituitary gland size, and anterior pituitary dysfunction. The association of mismatch pattern with specific underlying conditions needs further investigation. As patients with mismatch show stabilization of PS size, we assume a prognostic role of this peculiar pattern, which could be used to lead follow-up.

Abstract 3127: To investigate the role of BRAF V600E co-occurring mutations in Langerhans cell histiocytosis (LCH)

Abstract a. Introduction : Langerhans cell histiocytosis (LCH) is an inflammatory myeloid neoplasia caused by alterations of several genes in the MAPKinase pathway. The cell of origin is a white blood cell known as a dendritic cell priviously called as histiocyte characterized by a unique cytoplasmic organelle, the Birbeck granule, and the expression of CD1a and class II major histocompatibility complex molecules . The mutations cause these dendritic cells to attract other white blood cells and cause a “lesion” in any organ of the body. LCH has multi-orgnan involvement affecting skin bones, lymph nodes, brain etc. Systemic symptoms may include fever, bone pain, weight loss, jaundice, diabetes insipidus. b. Description: LCH is a rare sporadic, non-hereditary and non-malignant disease with unknown etiology characterized with a clonal proliferation of pathologic cells.Recent discovery of recurrent somatic mutations, BRAFV600E in MAPK pathway genes at critical stages of myeloid hematopoietic differentiation in LCH patients supports redefinition of the disease as a myeloproliferative disorder and provides opportunities to develop novel approaches to diagnosis and therapy. In the present proposal, we intend to analyze the BRAFV600E status along with other co-occurring mutations in a cohort of pediatric LCH patients by DNA sequencing in bone marrow samples or Peripheral Blood. Additionally we approach the above unanswered questions by applying an improved machine learning approach for classification and defining an algorithm for disease into different clusters for immediate clinical implication and to address its clinical heterogeneity. c. Results : We screened about 5 LCH patients and performed tageted exome seq to asertain the mutational profile of these patients. Sequencing detected BRAF V600E mutation in 3 of 5 samples for a mutation frequency of 60%. IHC based immunofloroscence shows that the intensity of phospho-MEK and phospho-ERK staining shows no significant alterations samples with mutation in BRAF. We are currently investigating mutations in other members of MAK pathways d. Conclusion : BRAF-V600E mutations were detected in few of our LCH patients. Neverless seeing the disease heterogeneity, we expect additionall mutations. More studies are needed to investigate mutations in the MAPK pathways that could efffect the course of disease management.We further plan to integrate the clinical and genomic findings to design a predictive model for the disease outcome. Citation Format: Subhradip Karmakar, R Dhar, K Purkayastha, R Seth, S Karmakar. To investigate the role of BRAF V600E co-occurring mutations in Langerhans cell histiocytosis (LCH) [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3127.

Egyptian experience in Langerhans cells histiocytosis: frequent multisystem affection and reactivation rates

Background: Histiocytoses are unique disorders; their clinical presentations vary from self-healing lesions to life-threatening disseminated disease. Objectives: We aimed to evaluate the different clinical presentations, frequency of reactivations, and treatment outcome of Langerhans cell histiocytosis among Egyptian children. Methods: we restrospectively analyzed the data of 37 Langerhans cell histiocytosis patients (LCH) registered at Ain Shams University Children’s Hospital for clinicopathological features, treatment modalities and their outcomes. Results: Twenty seven (73%) of the studied patients with LCH had multisystem disease (MS), 24 (88.9%) of them had risk organ involvement (MS RO+) and only 3 without risk organ (MS RO-). Most of the patients received LCH III protocols. Eleven patients (29.7%) had reactivations with median time till reactivation of 17 months (IQR 5-23).Reactivation rates were 40% and 50% in patients with no evidence of active disease (NAD) and those with active disease better (AD better) at week 6 evaluation respectively (p = 0.71).We report 9 deaths (all had MS RO+, two died after reactivation and 7 had progressive disease. The 5 years EFS and OS were 49.4% and 81.2% respectively. Risk stratification did not significantly affect the EFS or OS (p = 0.64 and p = 0.5 respectively). Conclusion: A high reactivation rate was encountered in children with LCH and MS-RO + irrespective of 6 weeks response to induction therapy. A high mortality in patients with progressive disease necessitates a possible earlier aggressive salvage in such group.

Nail involvement in Langerhans cell histiocytosis: Diagnostic and prognostic Clues

&nbsp; Introduction: Despite its rarity, nail involvement in Langerhans cell histiocytosis (LCH) may show various clinical presentations. This study aims to show the roles of nail involvement in LCH patients as the diagnostic and prognostic clues. Case illustrations: We presented four cases of multisystem LCH in children which were already confirmed by skin biopsy with various nail abnormalities. We were able to perform nail biopsy in two patients and confirmed the nail involvement. Histopathological examination showed the infiltration of Langerhans cells characterized by indented/reniform nuclei and CD1a expressions. All patients had high-risk organ involvements. Discussion: Langerhans cells may infiltrate the nail bed, proximal nail fold, and nail matrix. Further infiltration may destruct the nail plate. Hypothetically, we suggest that the nail bed as the initial infiltration site of Langerhans cells. The different sites of involvement lead to different clinical presentation. Nail abnormalities may predict a poorer prognosis, as they mostly occur in patients with multisystem disease. Conclusions: Nails should be routinely inspected in the suspicion of LCH. The presence of nail abnormalities in LCH patients may predict a poorer prognosis. Keywords: nail, Langerhans cell histiocytosis, diagnosis, prognosis &nbsp;

Correlative study of disease activity in Langerhans cell histiocytosis.

e19540 Background: Langerhans cell histiocytosis (LCH) is an inflammatory myeloid neoplasia that primarily affects younger children, most often involving bone, skin, lung, lymph nodes, or liver. Current treatment for LCH includes chemotherapy and biologically targeted therapies. Given its clinical heterogeneity and low prevalence, decision-making regarding intervention relies on subjective evaluation of disease status, which is often dependent on provider experience. Thus, there is a need to identify biomarkers for disease recurrence and activity in patients with LCH. Methods: We conducted a retrospective cohort study including pediatric LCH patients (n = 48) ≤21 years of age with biopsy-proven diagnosis of LCH and ≥1 year of follow-up after diagnosis. Data regarding demographics, symptom history, organ system involvement, and laboratory values at different time points were extracted from the from patient medical records and entered into a REDCap Database. The primary outcome was recurrence status as measured by the end of the study period. Data were analyzed using Stata statistical analysis software. Results: In our cohort, the sample was 64.6% Male and 35.4% Female with a median age of 29 months at diagnosis. 68.1% of patients had single organ involvement while 31.9% exhibited multi-system involvement. 70.8% of our cohort received treatment with chemotherapy with an average initial treatment duration of 12.1 months. 27.1% of the cohort experienced recurrence by the time of chart review. Logistic regression of the demographic factors and lab values at diagnosis revealed a statistically significant association between multi-system involvement (OR: 3.94, p = 0.04), moderate or high central nervous system risk assessment (OR: 7.67, p = 0.03; OR: 5.75, p = 0.03) and likelihood of recurrence. Additionally, logistic regression analysis revealed that alkaline phosphatase level at the time of diagnosis was associated with a slightly decreased likelihood of recurrence (OR: 0.987, p = 0.02). Conclusions: These results reveal that in addition to the traditionally utilized inflammatory markers (Erythrocyte Sedimentation Rate, White Blood Cell and Platelet Count), Alkaline Phosphatase could be used as a predictor of disease activity for patients with LCH, especially for those with bone involvement. Moving forward, an increased sample size might reveal other correlative biomarkers that can predict disease activity, helping to more precisely manage LCH.

Foxp3+ Tregs from Langerhans cell histiocytosis lesions co-express CD56 and have a definitively regulatory capacity

Langerhans cell histiocytosis (LCH) lesions contain myeloid lineage ‘LCH’ cells. Regulatory T cells (Tregs) are also enriched within lesions, although their role in LCH pathogenesis is unknown. LCH cells are thought to produce the transforming growth factor beta (TGF-β) within lesions, however whether Tregs contribute is unestablished. Using flow cytometry, we analyzed relative frequencies of live Tregs from LCH patients and identified CD56 expression and TGF-β production by lesion Tregs. While CD56+ Tregs were enriched in lesions, overall CD56+ T cells were reduced in the blood from active LCH patients compared to non-active disease patients, and there was a negative correlation between CD8+CD56+ T cells and Tregs. We propose that inducing a Treg phenotype in T cells such as CD56+ T cells may be a mechanism by which LCH cells divert inflammatory T cell responses. Thus, Tregs within LCH lesions are likely an important component in LCH pathogenesis.

Long-term efficacy and safety of 2CdA (cladribine) in extra-pulmonary adult-onset Langerhans cell histiocytosis: analysis of 23 cases from the French Histiocytosis Group and systematic literature review.

Langerhans cell histiocytosis (LCH) is a rare protean disease that usually affects children. Few data are available for management of adult-onset cases. A complete picture of the efficacy and safety of 2CdA (2-chlorodeoxyadenosine, cladribine) is lacking. We report a retrospective multicentre study of 23 adult LCH (a-LCH) patients who received single-agent 2CdA and a systematic literature review. All had previously received systemic therapy (vinblastine, n=19). Response to 2CdA was evaluable in 22 cases. Overall response rate (ORR) was 91%. Complete response (CR) occurred in 11 cases (50%). Nine patients (39%) developed grade 3-4 neutropenia and/or severe infection. A literature review yielded 48 additional cases. A pooled analysis confirmed our findings (ORR: 88%, CR: 49%). CRs were rare with cumulative dose <50mg/m2 . Disease progression rates were 20% and 30% at two and fiveyears, respectively. Partial response (PR) to 2CdA was predictive of disease progression. Among eight re-treated patients, five went into CR, two in PR, and one died. Single-agent 2CdA is effective in reactivated a-LCH, including at intermediate doses. Toxicity, significant but acceptable, warrants infectious prophylaxis. Complete responders may enter prolonged remission. Further studies are needed to determine 2CdA sequencing with other agents (vinblastine, cytarabine).

Pathophysiology and treatment of adult Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is a rare disease characterized by tissue infiltration of clusters of CD1a+/CD207+ histiocyte-like cells and a resultant surrounding inflammatory reaction. Because of its morphological similarity to cutaneous Langerhans cells, LCH was formerly named histiocytosis X in 1987. However, its cell lineage appears closely related to myeloid dendritic cells. In 2010, BRAF-V600E was detected in biopsy specimens from the majority of LCH patients. The subsequent observation of extracellular signal-regulated kinase phosphorylation in almost all LCH samples suggested that LCH was a neoplasm provoked by activation of the mitogen-activated protein (MAP) kinase pathway. Therefore, the 2016 Revised Classification by the Histiocyte Society defined LCH as an inflammatory myeloid neoplasm. Although a series of global and domestic clinical trials have improved the prognosis of pediatric LCH patients, no standard therapy with a high level of evidence for adult cases exists. Generally, LCH patients have a favorable prognosis, but delayed diagnosis and intervention may cause severe damage to the involved organs, resulting in a poor quality of life. Here we present recent advances in the pathophysiology and treatment of LCH to enlighten the understanding of this orphan disease.

Comparison of three different ELISAs for the detection of recombinant, native and plasma IL-17A

Plasma IL-17A detection in Langerhans Cell Histiocytosis (LCH) is currently a source of debate. Indeed, 500-P07G (PeproTech) and 41802 (R&D Systems) anti-IL-17A antibodies have been suspected to recognize nonspecific proteins. To resolve this discrepancy, we set up two new ELISAs by using 41802 or neutralizing eBio64CAP17 (eBioscience) capture monoclonal antibodies that we compared to the commercial PeproTech ELISA kit. The three ELISAs, called E_500-P07G, E_41802 and E_eBio64CAP17, differ in their anti-IL-17A capture antibodies: either polyclonal, monoclonal or neutralizing monoclonal antibodies, respectively. Here, we show that these ELISAs had a similar capacity to specifically detect recombinant or native human IL-17A. However, a significantly lower plasma IL-17A detection was obtained with E_41802 compared to the two other ELISAs. Both E_500-P07G and E_eBio64CAP17 showed similar results. Consequently, we propose that the use of E_500-P07G and E_eBio64CAP17 may ensure more accurate and reliable results in the context of LCH studies. The highest plasma IL-17A levels in LCH patients compared to controls detected by both E_500-P07G and E_eBio64CAP17 ELISAs led us to propose these latter as reference techniques to investigate IL-17A as a potential new biomarker in LCH.•The customization of a new E_eBio64CAP17 ELISA is suitable to detect human IL-17A.•E_eBio64CAP17 ELISA protocol differs only in the anti-IL-17A capture antibody compared to the commercial E_500-P07G PeproTech kit.•Data generated using the E_eBio64CAP17 ELISA are consistent with the PeproTech kit.

Genetic landscape of adult Langerhans cell histiocytosis with lung involvement

The clinical significance of the BRAF V600E mutation in adult Langerhans cell histiocytosis (LCH), including pulmonary Langerhans cell histiocytosis (PLCH), is not well understood. Similarly, the spectrum of molecular alterations involved in adult LCH has not been fully delineated. To address these issues, we genotyped a large number of adult LCH biopsies and searched for an association of identified molecular alterations with clinical presentation and disease outcome.Biopsies from 117 adult LCH patients, 83 with PLCH (median age 36.4 years, 56 females, 38 multisystem disease, 79 single system disease, 65 current smokers) were genotyped for the BRAF V600E mutation. In 69 cases, LCH lesions were also genotyped by whole-exome sequencing (WES) or targeted gene panel next-generation sequencing (NGS). Cox models were used to estimate the association of baseline characteristics with the hazard of LCH progression.MAPK pathway alterations were detected in 59 out of 69 cases (86%) (BRAF V600E mutation: 36%, BRAF N486_P490 deletion: 28%, MAP2K1 mutations: 15%, isolated NRAS Q61 mutations: 4%), while KRAS mutations were virtually absent in PLCH lesions. The BRAF V600E mutation was not associated with LCH presentation at diagnosis, including smoking status and lung function, in PLCH patients. BRAF V600E status did not influence the risk of LCH progression over time.Thus, MAPK alterations are present in most lesions from adult LCH patients, particularly in PLCH. Unlike reports in paediatric LCH, BRAF V600E genotyping did not provide additional information on disease outcome. The search for alterations involved in the MAPK pathway, including BRAF deletions, is useful for guiding targeted treatment in selected patients with refractory progressive LCH.

Altered cerebral perfusion in children with Langerhans cell histiocytosis after chemotherapy.

Children with Langerhans cell histiocytosis (LCH) may develop a wide array of neurological symptoms, but associated cerebral physiologic changes are poorly understood. We examined cerebral hemodynamic properties of pediatric LCH using arterial spin-labeling (ASL) perfusion magnetic resonance imaging (MRI). A retrospective study was performed in 23 children with biopsy-proven LCH. Analysis was performed on routine brain MRI obtained before or after therapy. Region of interest (ROI) methodology was used to determine ASL cerebral blood flow (CBF) (mL/100g/min) in the following bilateral regions: angular gyrus, anterior prefrontal cortex, orbitofrontal cortex, dorsal anterior cingulate cortex, and hippocampus. Quantile (median) regression was performed for each ROI location. CBF patterns were compared between pre- and posttreatment LCH patients as well as with age-matched healthy controls. Significantly reduced CBF was seen in posttreatment children with LCH compared to age-matched controls in angular gyrus (P=.046), anterior prefrontal cortex (P=.039), and dorsal anterior cingulate cortex (P=.023). Further analysis revealed dominant perfusion abnormalities in the right hemisphere. No significant perfusion differences were observed in the hippocampus or orbitofrontal cortex. Perfusion in specific cerebral regions may be consistently reduced in children with LCH, and may represent effects of underlying disease physiology and/or sequelae of chemotherapy. Studies that combine a formal cognitive assessment and hemodynamic data may further provide insight into perfusion deficits associated with the disease and the potential neurotoxic effects in children treated by chemotherapy.

The influence of clinical features mimicking primary immunodeficiency diseases (mPID) on children with Langerhans cell histiocytosis (LCH) - Four with mPID among 39 LCH children from one referral center during 18-year period.

Recurrent or refractory infections can be a warning sign of primary immunodeficiency diseases (PID). Such mimicking PID (mPID) can occur in patients with Langerhans cell histiocytosis (LCH). Because some cases with refractory molluscum contagiosum-like lesions and persistent otorrhea are finally diagnosed with LCH, we wondered whether such mPID can occur in LCH children and affect on their prognosis. We retrospectively reviewed all children with LCH at our institute from 2001 to 2018. A complete medical review of sex, age, symptoms, treatment course, and outcome comparison was performed. Of 39 enrolled LCH patients, three had persistent otorrhea and one had refractory molluscum contagiosum-like lesions despite aggressive antibiotic therapy. These four cases with mPID had significantly higher rates of multi-system involvement, recurrence and 5-month more lag time, but no risk organ (liver, spleen and bone marrow) involvement compared to those without mPID, although bone and skin were the most involved in both groups. Overall, the lag-time in multi-system was longer than that in single-system involvement (median 2.5 vs. 1.0 months; p = 0.003). The diagnosis-age of risk organ involvement was younger than those without (median 8 vs. 43 months; p = 0.004). There were no significant differences in diagnosis-age, single/multi-system and risk organ involvement between remission and recurrence groups. All were alive excluding four who were lost to follow-up. The LCH children with mPID had greater lag time, multi-system involvement, recurrence and more refractory treatment including transplantation despite the ratio of bone and skin lesions equal to those without mPID.

Low-Dose BRAF-Inhibitors in the Treatment of Histiocytic Disorders with the BRAF-V600E Mutation

Introduction: The landmark VE-BASKET trial demonstrated that Erdheim-Chester disease (ECD) patients with the BRAF-V600E mutation can be effectively treated with vemurafenib 1920 mg/day. However, all patients required dose reductions due to adverse effects. The efficacy of low dose BRAF-inhibitors is not well established in ECD. Further, as Langerhans cell histiocytosis (LCH) also harbors BRAF-V600E mutations in 50-60% of patients, BRAF-inhibitors may be effective in this disease as well. In this study, we evaluated the efficacy of low dose BRAF-inhibitors (vemurafenib and dabrafenib) in the treatment of ECD and LCH. Methods: We conducted a retrospective study of ECD and LCH patients who were seen at our institution from January 1998 to July 2018. All patients had a diagnosis of ECD and LCH determined by clinical criteria in conjunction with histopathologic findings. Based on the standard doses approved for malignant melanoma and ECD, patients were categorized into the low dose BRAF-inhibitor group if they were treated with vemurafenib &lt; 960 mg/day or dabrafenib ≤ 150mg/day at any point in time. We used a simple response criteria that defined clinical progressive disease (PD) as worsening of symptoms attributed to ECD/LCH or radiologic PD as a progression or worsening of proven or suspected lesions due to ECD/LCH. The minimum duration for symptom improvement to be considered a response was set at 3 months. Results: A total of 89 ECD patients and 186 LCH patients were identified. Within the ECD cohort, 24 of 44 (55%) patients who were tested had the BRAF-V600E mutation. Eight patients were included in the low dose BRAF-inhibitor group. The median age at diagnosis was 57 years (range 37-74) and 5 (63%) were male. The most common areas of involvement included bone (88%), cardiovascular system (63%), kidneys (63%), and brain parenchyma (50%). The median time of follow up was 66 months (range 23-165) and the median time on low-dose BRAF-inhibitor was 10 months (range 1-27) [Table 1]. Three patients had a starting dose of vemurafenib 1920 mg/day, 4 had 960 mg/day, and 1 had 480 mg/day. All patients required dose reductions and 50% of the patients ultimately discontinued vemurafenib due to side effects. Side effects included fatigue, pruritus, nausea, facial swelling, blisters, papillomas, and/or subcutaneous nodules. Four patients were able to remain on low-dose vemurafenib for a median follow up time of 24.5 months (range 12-28) with ongoing response and no signs of clinical or radiologic PD. Within the LCH cohort, 18 of 31 tested (58%) patients had the BRAF-V600E mutation. Four patients were included in the low dose BRAF-inhibitor group. The median age at diagnosis of this cohort was 43 years (range 34-69) and 2 (50%) were male. Areas of involvement included bone (100%), brain parenchyma (hypothalamus/optic stalk and pons; 50%), and skin (25%). The median time of follow up was 31 months (range 21-46) and the median time on low-dose BRAF-inhibitor was 4 months (range 3-24) [Table 2]. Two patients had a starting dose of vemurafenib 960mg/day. The patients with brain parenchymal involvement had a starting dose of dabrafenib 150mg/day or 100mg/day. All patients taking vemurafenib 960mg/day required dose reductions and one patient discontinued treatment due to skin blistering in her feet. In the patients taking dabrafenib, no side effects have yet been reported. 3 patients had an ongoing response and did not have clinical or radiologic PD. Patient #10 however, had clinical and radiologic PD after being on vemurafenib 720mg/day for 22 months. Conclusion: Our study suggests a potential role for lower doses of BRAF-inhibitors in ECD and LCH patients harboring BRAF-V600E mutations. Dabrafenib was found to be particularly efficacious and well-tolerated in LCH involving the brain parenchyma. However, patients who undergo dose reductions should be closely monitored due to the risk of disease progression. Careful balance of toxicities and efficacy is needed for optimizing patient outcomes with targeted therapies. Disclosures Bennani: Adicet Bio: Other: Advisory board; Kite Pharma: Other: Advisory board; Purdue Pharma: Other: Advisory board; Purdue Pharma: Other: Advisory board; Seattle Genetics: Other: Advisory board; Purdue Pharma: Other: Advisory board; Adicet Bio: Other: Advisory board; Kite Pharma: Other: Advisory board; Bristol-Myers Squibb: Research Funding; Bristol-Myers Squibb: Research Funding; Adicet Bio: Other: Advisory board; Bristol-Myers Squibb: Research Funding; Kite Pharma: Other: Advisory board; Seattle Genetics: Other: Advisory board; Seattle Genetics: Other: Advisory board. OffLabel Disclosure: Vemurafenib and dabrafenib for Langerhans cell histiocytosis. Vemurafenib dosage for Erdheim-Chester disease is less than the approved dose of 960mg every 12 hours.

Molecular Alterations in Adult Histiocytic Neoplasms

Introduction Histiocytic neoplasms are rare disorders of the monocyte-macrophage-dendritic cell lineage that pose significant management challenges to the clinicians. Over the last five years, there has been emerging data on the role of MAPK/ERK pathway (RAS-RAF-MEK-ERK) in their pathogenesis. In this study, we report the molecular alterations among patients with histiocytic neoplasms seen at our institution. Methods We pursued target-capture next generation sequencing (NGS) on tissue specimen of patients with various histiocytic neoplasms- Erdheim-Chester disease (ECD), Langerhans cell histiocytosis (LCH), Rosai-Dorfman disease (RDD), histiocytic sarcoma (HS), and Langerhans cell sarcoma (LCS). We used three NGS platforms, Tempus® xO (1,714 genes), Tempus® xT (596 genes), or Foundation One® CDX (324 genes). All platforms used formalin-fixed paraffin-embedded tumor tissue specimens for detection of substitutions, insertion and deletion alterations, and copy number alterations, and gene rearrangements. The Tempus assays also utilized matched blood or saliva samples for germline DNA sequencing in addition to whole-transcriptome RNA sequencing. The tumor cellularity threshold for pursuing RNA sequencing was 30% so the test was not pursued specimens for lower cellularity. Results We included 31 cases with histiocytic neoplasms in this study. The disease distribution was as follows: ECD (n=6), LCH (n=7), RDD (n=12), ECD-RDD overlap (n=3), HS (n=2), and LCS (n=1). Among the 13 patients with ECD and LCH, BRAF-V600E mutations were found in 8 (62%) cases. We found several novel DNA alterations in this study in all disease groups: ECD (BRAFV471F), LCH (MAP2K1 in-frame deletion), and RDD (frameshift mutations of DNMT3A, SMARCA4, KMT2A, and CDC73 truncation). In one LCH patient without any DNA alterations, we found MAPK1 and MAP2K1 overexpression on RNA sequencing. We also had two cases with HS, both of which were found to have KRAS exon 3 mutations. One of these cases had concomitant JAK2V617F+ myelofibrosis and the tissue specimen for HS demonstrated TET2 and SRSF2 mutations as well. Our cohort included one patient with multifocal lymph node LCS that demonstrated NRAS and TP53 mutations, who did not respond to MEK-inhibitor therapy. Alterations in epigenetic regulators (TET2, DMNT3A, KMT2A, ASXL1) were found in 5 (16%), potentially suggesting clonal hematopoiesis in a subgroup of histiocytosis. Conclusions Histiocytic neoplasms demonstrate diverse somatic oncogenic alterations. In our study, we noted several novel alterations beyond the MAPK-ERK pathway in RDD that may point toward other potentially pathogenic mechanisms for these rare disorders. In cases where the DNA sequencing does not reveal pathogenic alterations, transcriptome analysis may aid in the diagnosis and management. OffLabel Disclosure: Trametinib use for Langerhans cell sarcoma

BRAFV600E-Positive Precursors As Molecular Markers of Bone Marrow Involvement in Pediatric Langerhans Cell Histiocytosis

Introduction: The BRAF mutation V600E, the most common somatic mutation in Langerhans cell histiocytosis (LCH), has been reported in approximately 50% of LCH patients and is associated with certain high-risk clinical features. Precursors harboring this mutation can differentiate into Langerhans cells resulting in infiltrates in multiple organs under inflammatory conditions. However, BRAF status in the bone marrow of pediatric LCH patients is unclear. The present study examined somatic mutations in paired tumor and bone marrow samples, using a highly sensitive assay involving next-generation targeted sequencing and droplet digital polymerase chain reaction (PCR) for pediatric LCH patients. Methods: Between 1996 and 2019, in total of 17 Japanese pediatric patients with LCH were enrolled. The male/female ratio was 7/11. Ages of onset of LCH were median 13 months (range 5-193 months). At diagnosis of LCH, 2 patients were positive for risk organ involvement, 15 were negative. We retrospectively performed mutational analyses of 17 LCH cases using formalin-fixed paraffin-embedded LCH tumor specimens to provide templates for PCR-based targeted amplicon sequencing with customized primers to detect mutations in exons 12 and 15 in BRAF, and exons 2 and 3 in MAP2K1. Thereafter, we identified somatic mutations in the 17 paired bone marrow samples via droplet digital allele-specific PCR, targeting BRAF V600E and BRAF exon 12 in-frame deletion 496-500 (Ex12 in-del). Results: We detected BRAF V600E in 11 of 17 tumor samples (65%) and the BRAF Ex 12 in-del in 3 of 17 tumors (18%). We identified BRAF V600E in bone marrow samples in 10 of the 11 cases (90%) with the mutation in the tumor at low variant allele frequency (median 0.25%, range 0.14-7.0%). BRAF Ex 12 in-del was not detected in the bone marrow. Cases with detectable bone marrow involvement included eight patients with multi-system disease affecting multiple organs, one patient with multi-focal bone disease, and one patient with single-system disease. Clinical phenotypes including relapse did not correlate with BRAF V600E upon detection in the bone marrow. Conclusion: We established the sensitive assay based on PCR-based targeted NGS for detecting somatic mutations in LCH even accessible for formalin-fixed, paraffin-embedded clinical specimens. Bone marrow involvement is frequently detectable at the molecular level in pediatric LCH with the BRAF V600E mutation. A prospective study is warranted to evaluate the clinical impact of mutational burden in bone marrow. Disclosures Kudo: Unum Therapeutics: Patents &amp; Royalties. Imai:Juno Therapeutics: Patents &amp; Royalties.