Single-system Langerhans Cell Histiocytosis Research Articles

Genetic Landscape and Its Prognostic Impact in Children With Langerhans Cell Histiocytosis.

Langerhans cell histiocytosis (LCH) is a rare myeloid neoplasm that predominantly affects young children. To investigate genetic alterations and their correlation with clinical characteristics and prognosis in pediatric LCH. We performed targeted sequencing to detect mutations in LCH lesions from pediatric patients. A total of 30 genomic alterations in 5 genes of the MAPK pathway were identified in 187 of 223 patients (83.9%). BRAF V600E (B-Raf proto-oncogene, serine/threonine kinase) was the most common mutation (51.6%), followed by MAP2K1 (mitogen-activated protein kinase kinase 1) alterations (17.0%) and other BRAF mutations (13.0%). ARAF (A-Raf proto-oncogene, serine/threonine kinase) and KRAS (KRAS proto-oncogene, GTPase) mutations were relatively rare (2.2% and 0.9%, respectively). Additionally, FNBP1 (formin-binding protein 1)::BRAF fusion and MAP3K10 (mitogen-activated protein kinase kinase 10) mutations A17T and R823C were identified in 1 case each, with possible constitutive activation of ERK1/2 phosphorylation. BRAF V600E was more frequent in patients with risk organ involvement, while MAP2K1 mutation was more prevalent in patients with single-system LCH (P = .001). BRAF V600E was associated with craniofacial bone, skin, liver, spleen, and ear involvement (all P < .05). Patients with other BRAF mutations had a higher proportion of spinal column involvement (P = .006). Univariate analysis showed a significant difference in progression-free survival among the 4 molecular subgroups for patients treated with first-line therapy (P = .02). According to multivariate analysis, risk organ involvement was the strongest independent adverse prognostic factor (hazard ratio, 8.854; P < .001); BRAF or MAP2K1 mutation was not an independent prognostic factor. Most pediatric patients with LCH carry somatic mutations involving the MAPK pathway, correlating with clinical characteristics and outcomes for first-line chemotherapy.

Dabrafenib and trametinib in Langerhans cell histiocytosis and other histiocytic disorders.

The standard treatment for Langerhans cell histiocytosis (LCH) is chemotherapy, although the failure rates are high. Since MAP-kinase activating mutations are found in most cases, BRAF- and MEK-inhibitors have been used successfully to treat patients with refractory or relapsed disease. However, data on long-term responses in children are limited and there are no data on the use of these inhibitors as first-line therapy. We treated 34 patients (26 with LCH, 2 with juvenile xanthogranuloma, 2 with Rosai-Dorfman disease, and 4 with presumed single site-central nervous system histiocytosis) with dabrafenib and/or trametinib, either as first line or after relapse or failure of chemotherapy. Sixteen patients, aged 1.3-21 years, had disease that was recurrent or refractory to chemotherapy, nine of whom had multisystem LCH with risk-organ involvement. With a median treatment duration of 4.3 years, 15 (94%) patients have sustained favorable responses. Eighteen patients, aged 0.2-45 years, received an inhibitor as first-line treatment. All of these have had sustained favorable responses, with a median treatment duration of 2.5 years. Three patients with presumed isolated central nervous system/pituitary stalk histiocytosis had stabilization or improvement of their disease. Overall, inhibitors were well tolerated. Five patients with single-system LCH discontinued therapy and remain off therapy without recurrence. In contrast, all four patients with multisystem disease who discontinued therapy had to restart treatment. Our data suggest that children suffering from histiocytoses can be treated safely and effectively with dabrafenib or trametinib. Additional studies are, however, needed to determine the long-term safety and optimal duration of therapy.

Clinical and prognostic features of Langerhans cell histiocytosis in adults.

Langerhans cell histiocytosis (LCH) is a rare disease characterized by clonal expansion of CD1a+ CD207+ myeloid dendritic cells. The features of LCH are mainly described in children and remain poorly defined in adults; therefore, we conducted a nationwide survey to collect clinical data from 148 adult patients with LCH. The median age at diagnosis was 46.5 (range: 20-87) years with male predominance (60.8%). Among the 86 patients with detailed treatment information, 40 (46.5%) had single system LCH, whereas 46 (53.5%) had multisystem LCH. Moreover, 19 patients (22.1%) had an additional malignancy. BRAF V600E in plasma cell-free DNA was associated with a low overall survival (OS) rate and the risk of the pituitary gland and central nervous system involvement. At a median follow-up of 55 months from diagnosis, six patients (7.0%) had died, and the four patients with LCH-related death did not respond to initial chemotherapy. The OS probability at 5 years post-diagnosis was 90.6% (95% confidence interval: 79.8-95.8). Multivariate analysis showed that patients aged ≥60 years at diagnosis had a relatively poor prognosis. The probability of event-free survival at 5 years was 52.1% (95% confidence interval: 36.6-65.5), with 57 patients requiring chemotherapy. In this study, we first revealed the high rate of relapse after chemotherapy and mortality of poor responders in adults as well as children. Therefore, prospective therapeutic studies of adults with LCH using targeted therapies are needed to improve outcomes in adults with LCH.

Multiple Langerhans cell histiocytosis with spinal involvement.

The aim of this study was to report the long-term prognosis of patients with multiple Langerhans cell histiocytosis (LCH) involving the spine, and to analyze the risk factors for progression-free survival (PFS). We included 28 patients with multiple LCH involving the spine treated between January 2009 and August 2021. Kaplan-Meier methods were applied to estimate overall survival (OS) and PFS. Univariate Cox regression analysis was used to identify variables associated with PFS. Patients with multiple LCH involving the spine accounted for 15.4% (28/182 cases) of all cases of spinal LCH: their lesions primarily involved the thoracic and lumbar spines. The most common symptom was pain, followed by neurological dysfunction. All patients presented with osteolytic bone destruction, and 23 cases were accompanied by a paravertebral soft-tissue mass. The incidence of vertebra plana was low, whereas the oversleeve-like sign was a more common finding. The alkaline phosphatase was significantly higher in patients with single-system multifocal bone LCH than in patients with multisystem LCH. At final follow-up, one patient had been lost to follow-up, two patients had died, three patients had local recurrence, six patients had distant involvement, and 17 patients were alive with disease. The median PFS and OS were 50.5 months (interquartile range (IQR) 23.5 to 63.1) and 60.5 months (IQR 38.0 to 73.3), respectively. Stage (hazard ratio (HR) 4.324; p < 0.001) and chemotherapy (HR 0.203; p < 0.001) were prognostic factors for PFS. Pain is primarily due to segmental instability of the spine from its destruction by LCH. Chemotherapy can significantly improve PFS, and radiotherapy has achieved good results in local control. The LCH lesions in some patients will continue to progress. It may initially appear as an isolated or single-system LCH, but will gradually involve multiple sites or systems. Therefore, long-term follow-up and timely intervention are important for patients with spinal LCH.

Adult Onset Langerhans Cell Histiocytosis: Clinical Characteristics and Treatment Outcomes

PurposeLangerhans cell histiocytosis (LCH) is a rare disease that can affect all tissues and organs. Our study evaluated the clinical characteristics and treatment outcomes of adult-onset LCH patients in a tertiary center.Materials and MethodsAdult patients diagnosed with LCH were retrospectively evaluated. Their initial symptoms, stratification according to disease involvement, treatment details, treatment responses, and overall and progression-free survival (PFS) were analyzed.ResultsThirty-three patients were included. There were 21 single system LCH, 10 multisystem LCH, and 2 pulmonary LCH patients. Patients with single system unifocal involvement were successfully treated with local therapies such as surgery and radiotherapy. Most of the multisystem LCH patients and patients with single system multifocal involvement were treated with systemic chemotherapy. Cladribine was the first choice in 10 out of 11 patients who received chemotherapy. Among all patients, the overall response rate (ORR) was 97%. Among those who had cladribine in the first-line the ORR was 81%. All these patients achieved a complete remission and were alive at the last visit. The median follow-up was 38 (range, 2–183) months. The median PFS has not yet been reached. Ten-year PFS was 90.9%.ConclusionBesides successful local treatments with surgery and radiotherapy, our study provides information for front-line cladribine treatment.

Clinical outcomes and prognostic risk factors of Langerhans cell histiocytosis in children: Results from the BCH-LCH 2014 protocol study.

Langerhans cell histiocytosis (LCH) is a rare myeloid neoplasm mainly affecting young children. This study aimed to evaluate the outcomes of 449 pediatric patients enrolled in the BCH-LCH 2014 study. 52.6% of patients were classified with single-system (SS) LCH, 28.1% with multisystem (MS) risk organ negative (RO-) LCH, and 19.4% with MS RO+ LCH. Three hundred ninety-six patients (88.2%) were initially treated with first-line therapy based on the vindesine-prednisone combination. One hundred thirty-nine patients who lacked a response to initial treatment were shifted to second-line therapy, 72 to intensive treatment Arm S1 (a combination of cytarabine, cladribine, vindesine, and dexamethasone), and 67 to Arm S2 (without cladribine). The 5-year overall survival (OS), progression-free survival (PFS), and relapse rates were 98.2% (median: 97.6months), 54.6% (median: 58.3months), and 29.9%, respectively. MS RO+ patients had the worst prognosis among the three clinical subtypes. For the patients initially treated with first-line therapy, the 5-year OS, PFS, and relapse rates were 99.2%, 54.5%, and 29.3%, respectively. Patients in Arm S1 had a significantly better prognosis than patients in Arm S2 (5-year PFS: 69.2% vs. 46.5%, p=.042; relapse rate: 23.4% vs. 44.2%, p=.031). Multivariate analysis revealed that early treatment response, the involvement of RO, skin, and oral mucosa, as well as laboratory parameters, including CRP and γ-GT, were independent risk factors for the PFS of LCH. Thus, the prognosis of LCH in children has been improved significantly with stratified chemotherapy, and progression and relapse remained the challenges, especially for RO+ patients.

Langerhans Cell Histiocytosis Presenting as a Lesser Trochanter Fracture in an Adolescent: A Case Report.

We present the case of an 18-year-old man with right hip pain who was found to have a lytic lesion of the lesser trochanter of the right femur with cortical destruction and a lytic lesion of the left inferior pubic ramus. Additional imaging and pathology testing confirmed a diagnosis of multifocal, single-system Langerhans cell histiocytosis (LCH) of the bone. LCH is a rare pediatric disease most commonly diagnosed in toddlers and young school-age children. Its epidemiologic characteristics are poorly described for young adults and older adolescents, in whom clinical suspicion should be maintained when evaluating multifocal osseous lesions.

Isolated Hepatobiliary Involvement in an Infant with Langerhans Cell Histiocytosis: A Case Report with Review of Literature

Background: Langerhans cell histiocytosis (LCH) is a rare condition in which there is the proliferation of cells of the monocyte-dendritic cell lineage, including Langerhan's cells, with variable clinical manifestations and outcomes. Hepatic involvement is often seen as a part of multi-system LCH and is associated with a fulminant course. Isolated hepatobiliary involvement in LCH is rare. Clinical Description: We report an 11-month-old female infant presenting with prolonged fever associated with progressive jaundice, clay-colored stools, and a massive hepatomegaly. Liver biopsy showed CD1a and Langerin positivity. There was no other system involvement, and hence, the infant was diagnosed with a case of single-system LCH with isolated hepato-biliary LCH. Management and Outcome: A customized chemotherapeutic regimen was started with cytarabine and prednisolone. The patient has responded and there has been gradual improvement in the general clinical condition as well as the laboratory parameters. Conclusions: This case report creates the awareness of possible presentation of pediatric LCH with isolated liver involvement. A high index of suspicion, carefully customized chemotherapeutic regimen may help in the timely diagnosis and successful management.

Application of 18F-FDG PET/CT in Langerhans Cell Histiocytosis.

Purpose This study aims to explore the application value of the 18F-FDG PET/CT imaging in diagnosing, staging, and typing Langerhans cell histiocytosis (LCH) via the morphological and metabolic analyses of the 18F-FDG PET/CT images. Methods We retrospectively analyzed the 18F-FDG PET/CT images and clinical data of nineteen patients with LCH. The shape, size, density, distribution, and 18F-FDG uptake of all lesions were documented. In addition, the SUVmax of the lesions, liver, and blood pool was measured prior to calculating the lesion-to-liver and lesion-to-blood pool ratios. Results Among the 19 analyzed patients, the positive rate of the PET/CT image was 94.7% (18/19), with 1 false negative (5.3%, 1/19) case occurring in the cutaneous LCH. Among the 76 lesions, 69 were FDG-avid lesions (69/76, 90.8%). Additionally, we observed no FDG uptake in 7 lesions (7/76, 9.2%). In contrast, 59 lesions (59/76, 77.6%) were abnormal on diagnostic CT scan, but 17 lesions (17/76, 22.4%) were undetected. The 18F-FDG PET/CT image revealed additional 6 lesions in the bone, 4 in the lymph node, 3 in the spleen, and 3 occult lesions, which CT scan did not detect. Additionally, there were 6 cases with single-system LCH. The remaining 13 cases were multisystem LCH. Our 18F-FDG PET/CT image analyses altered the typing of 4 LCH patients. In the case of all lesions, the mean SUVmax of the 18F-FDG-avid lesions was 5.4 ± 5.1 (range, 0.8∼26.2), and the mean lesion-to-liver SUVmax ratio was 3.1 ± 2.52 (range, 0.7∼11.9), and the mean lesion-to-blood pool SUVmax ratio was 4.6 ± 3.4 (range 0.7∼17.5). Conclusion The 18F-FDG PET/CT image plays an essential role in LCH diagnosis, primary staging, and typing. It can accurately evaluate the distribution, range, and metabolic information of LCH, providing a vital imaging basis for the clinical evaluation of disease conditions, selection of treatment schemes, and determining patient prognosis.

Langerhans cell histiocytosis of the rib in an adult: A case report and review of the literature.

Introduction and importanceLangerhans cell histiocytosis (LCH) is a rare neoplastic hyperplasia with an unknown etiology. It is clinically rare for patients with solitary rib lesion and pathological fracture. In this article, we report a case of LCH in solitary involvement of rib and provide a review of the available literature.Case presentationA 24-year-old female patient complained of right chest and back pain for 10 days. CT showed a fracture in the right 6th rib. Findings on X-ray, and CT were suggestive of homogeneous osteolytic lesion of the right 6th rib. The rib tumor was then resected and the surrounding muscles and soft tissues were accordingly resected.Clinical discussionThe patient was diagnosed with pathological rib fracture, and the patient was pathologically diagnosed with LCH. After surgery, no local recurrence or distant metastasis was reported during the one-year follow-up.ConclusionsMost of the solitary tumorous lesions in rib in adults call for various differential diagnoses. Although single-site, single-system LCH of the rib is one of the rarest causes of bone tumor in adults, it can be treated successfully with surgical intervention. LCH should be considered in the diagnosis of an adult patient with a rib mass.

Langerhans cell histiocytosis in adolescent patients: a single-centre retrospective study

BackgroundLangerhans cell histiocytosis (LCH) is a myeloid dendritic cell disorder frequently affecting children more than adults. The presentation of LCH varies with age, however, the clinical characteristics and genetic profiles of adolescent LCH remain elusive. To address the knowledge gap, we performed a single-centre retrospective study of 36 adolescent LCH patients aged between 14 and 17 years at Peking Union Medical College Hospital.ResultsAt the time of diagnosis, 10 patients were classified as unifocal single system LCH (27.8%), 2 patients had pulmonary single system LCH (5.6%), 5 patients had multifocal single system LCH with bone involvement (13.9%), and 19 patients had multisystem LCH (52.8%). The most prevalent involvement in multisystem patients was the pituitary gland (78.9%), followed by the bone (42.1%), lung (42.1%), and lymph nodes (42.1%). Eight (42.1%) patients had risk organ involvement. BRAFN486_P490 was detected in 50% of patients who underwent next generation sequencing, and BRAFV600E was detected in one patient. Chemotherapies were the first line treatment in 24 patients. One patient died and thirteen patients relapsed during the follow-up. The estimated 5-year OS rate and EFS rate were 94.7% and 59.0%, respectively.ConclusionsIn this study, we report a large series of adolescent LCH patients. The clinical characteristics of adolescent LCH patients may be close to adult LCH. Compared with pediatric cases, adolescent LCH tends to have more pituitary lesions and pulmonary involvement, fewer skin and hematopoietic involvement, a higher frequency of BRAF deletion mutation, and a lower frequency of BRAFV600E mutation.

Adult Langerhans cell histiocytosis with thyroid gland involvement: clinical presentation, genomic analysis, and outcome.

The present study aims to evaluate the characteristics and treatment outcomes of adult Langerhans cell histiocytosis (LCH) patients with thyroid involvement. We retrospectively described the clinical, biological, and genomic characteristics of a series of 36 LCH patients with thyroid involvement in our center between January 2001 and December 2021. At the time of diagnosis, only one patient was classified as having single-system LCH, and 35 patients were classified as having multisystem (MS) LCH. Three patients had coexisting papillary thyroid carcinoma. Patients with thyroid gland involvement had higher frequencies of pituitary (88.6% vs. 53.4%, P < 0.001), liver (45.7% vs. 20.7%, P = 0.003), and lymph node (54.3% vs. 31.6%, P = 0.012) involvement and a lower frequency of bone (45.7% vs. 72.0%, P = 0.003) involvement than patients without thyroid gland involvement. Sixteen patients had abnormal thyroid function, including nine patients with primary hypothyroidism, one patient with central hypothyroidism, and six patients with subclinical hypothyroidism. BRAFV600E, BRAF N486_P490, and MAP2K1 mutations were detected in 14.3%, 57.1%, and 7.1% of patients, respectively. After a 43-month median follow-up, none of the patients died, and 15 patients experienced reactivation. The median event-free survival was 37.5months. Two of 6 patients with subclinical hypothyroidism had normal thyroid function, and 12 patients still had hypothyroidism after treatment. As the largest adult LCH cohort with thyroid gland involvement to date, we found that patients with thyroid gland involvement had different clinical characteristics, genetic profiles, and outcomes than patients without thyroid gland involvement.

International expert consensus recommendations for the diagnosis and treatment of Langerhans cell histiocytosis in adults

AbstractLangerhans cell histiocytosis (LCH) can affect children and adults with a wide variety of clinical manifestations, including unifocal, single-system multifocal, single-system pulmonary (smoking-associated), or multisystem disease. The existing paradigms in the management of LCH in adults are mostly derived from the pediatric literature. Over the last decade, the discovery of clonality and MAPK-ERK pathway mutations in most cases led to the recognition of LCH as a hematopoietic neoplasm, opening the doors for treatment with targeted therapies. These advances have necessitated an update of the existing recommendations for the diagnosis and treatment of LCH in adults. This document presents consensus recommendations that resulted from the discussions at the annual Histiocyte Society meeting in 2019, encompassing clinical features, classification, diagnostic criteria, treatment algorithm, and response assessment for adults with LCH. The recommendations favor the use of 18F-Fluorodeoxyglucose positron emission tomography-based imaging for staging and response assessment in the majority of cases. Most adults with unifocal disease may be cured by local therapies, while the first-line treatment for single-system pulmonary LCH remains smoking cessation. Among patients not amenable or unresponsive to these treatments and/or have multifocal and multisystem disease, systemic treatments are recommended. Preferred systemic treatments in adults with LCH include cladribine or cytarabine, with the emerging role of targeted (BRAF and MEK inhibitor) therapies. Despite documented responses to treatments, many patients struggle with a high symptom burden from pain, fatigue, and mood disorders that should be acknowledged and managed appropriately.

Treatment outcomes and prognostic factors of patients with adult Langerhans cell histiocytosis.

Adult Langerhans cell histiocytosis (LCH) remains poorly defined. We retrospectively studied 266 newly diagnosed LCH patients to understand the clinical presentation, treatment, and prognosis of adult LCH. The median age at diagnosis was 32 years (range, 18-79 years). At the time of diagnosis, 40 patients had single lesions within a single system, 18 patients had single pulmonary LCH, 26 patients had multiple lesions within a single system (SS-m), and 182 patients had multisystem disease (MS). The most common organ involved in MS patients was the bone (69.8%), followed by the pituitary (61.5%) and lung (61.0%). BRAFV600E , BRAF deletion, and MAP2K1 mutation were detected in 38.8%, 25.4%, and 19.4% patients, respectively. BRAF deletion was found more common in patients with MS LCH compared to single-system LCH (38.5% vs 7.1%, p=.004), also in patients with liver involvement (69.2% vs 14.3%, p < .001). The estimated 3-year overall survival (OS) and event-free survival (EFS) rates were 94.4% and 54.7%, respectively, in SS-m and MS LCH. Multivariate Cox regression showed that involvement of the liver or spleen at baseline predicted poor EFS and receiving cytarabine-based therapy as a first-line treatment and age older than 30 years at diagnosis predicted favorable EFS. The involvement of risk organs and age older than 50 years predicted poor OS, and receiving cytarabine-based therapy predicted favorable OS. Therefore, BRAF deletion was correlated with MS LCH, particularly those with liver involvement. Liver or spleen involvement at baseline indicates a poor prognosis, and a cytarabine-based regimen could be considered as first-line treatment for adult LCH patients.

Clinical characteristics and outcomes of Langerhans cell histiocytosis at a single institution in Thailand: a 20-year retrospective study.

Langerhans cell histiocytosis (LCH) is a rare disease characterized by the various systems involved and clinical manifestations with a wide range of symptoms. To describe clinical characteristics, imaging, treatment, and outcomes of pediatric LCH at Phramongkutklao Hospital, Bangkok, Thailand. We conducted a 20-year retrospective review of the medical records of patients diagnosed with LCH from birth to 21 years old from January 1, 1997, to December 31, 2016. In all, 14 patients with median age of 2.5 years were studied. Six (43%) patients had single-system (SS) LCH. Five patients (63%) with multisystem (MS) LCH (n = 8. 57%) had risk-organ involvement (RO+). All patients had plain X-ray imaging of their skull with 11 (79%) showing abnormal findings. Tc-99m bone imaging and fluorodeoxyglucose F18 (FDG) positron emission tomography (PET)-computed tomography (CT) demonstrated abnormal findings in 8 (89%) and 4 (29%) patients, respectively. The 5-year event-free survival (EFS) for patients with RO+ MS-LCH was less than that for those without risk-organ involvement (RO-) MS-LCH and SS-LCH (20% vs. 100%, P = 0.005). Hematological dysfunction, hypoalbuminemia, and conjugated hyperbilirubinemia may be worse prognostic factors for RO+ MS-LCH. FDG-PET-CT might have a greater accuracy to detect LCH disease than conventional plain X-ray and Tc-99m bone imaging. RO+ MS-LCH has been encountered with relapse and poor outcomes. Hematopoietic involvement, hypoalbuminemia, and conjugated hyperbilirubinemia may be worse prognostic factors for RO+ MS-LCH.

Additive Prognostic Impact of Gastrointestinal Involvement in Severe Multisystem Langerhans Cell Histiocytosis

To evaluate the prognostic impact of gastrointestinal involvement on the survival of children with Langerhans cell histiocytosis(GI-LCH) registered with the international clinical trials of the Histiocyte Society. This was a retrospective analysis of 2414 pediatric patients registered onto the consecutive trials DAL-HX 83, DAL-HX 90, LCH-I, LCH-II, and LCH-III. Among the 1289 patients with single-system LCH, there was no single case confined to the GI tract; 114 of 1125 (10%) patients with multisystem LCH (MS-LCH) had GI-LCH at initial presentation. GI-LCH was significantly more common in children aged <2years at diagnosis (13% vs 6% in those aged >2years; P<.001) and in those with risk organ involvement (15% vs 6% in those without risk organ involvement; P<.001). The 5-year overall survival (OS) in patients without risk organ involvement was excellent irrespective of GI disease (98% vs 97% in patients with GI-LCH; P=.789). In patients with risk organ involvement, the 5-year OS was 51% in 70 patients with GI-LCH vs 72% in 394 patients without GI-LCH (P<.001). GI-LCH has an additive unfavorable prognostic impact in children with MS-LCH and risk organ involvement. The emerding need for more intensive or alternative treatments mandates prospective evaluation.

Clinical and prognostic characteristics of 95 cases of Langerhans cell histiocytosis in children: a single-institute experience from 2013 to 2020

Background This study aimed to understand the clinical characteristics and outcomes of children with Langerhans cell histiocytosis (LCH) in China. Methods We conducted a retrospective study of 95 paediatric patients with LCH in West China Second University Hospital of Sichuan University between July 2013 and August 2020. Results The onset age of multisystem LCH (MS-LCH) patients with risk organ (RO) involvement was younger than that of MS-LCH without RO involvement (p = .002) and single system LCH (p < .001) patients; bone was the most frequently involved organ, followed by the skin. Of all, the BRAF-V600E mutation was detected in 48 out of 84 patients who underwent gene analysis. Additionally, in our study, BRAF p.N486_T491 > K, BRAF p.L485_P490delinsF, BRAF p.R506_K507insLLR, ARAF p.Q349_F351delinsL and MAP2K1 p.Q58_E62del were known mutations in the mitogen-activated protein kinase (MAPK) pathway. The BRAF-V600E genotype in the tissue and plasma prior to therapy were detected in 16 patients, and the concordance was only 37.5% (6/16). According to the modified LCH-III-based-protocol, JLSG-02 protocol chemotherapy, and vemurafenib, the estimated five-year overall survival, event-free survival (EFS) and cumulative reactivation rates of 95 patients were 98.8%, 74.6% and 24.5%, respectively. The EFS rate in good responders was better than that in poor responders at 12-week (HR = 0.022, 95%CI 0.002–0.231, p = .002), and EFS was not affected by age, RO involvement or BRAF-V600E mutation. Regarding sequelae, nine patients had central diabetes insipidus and two had growth retardation. Conclusions In this study, LCH was a highly heterogeneous disease characterized molecularly by MAPK-pathway activating mutations. Vincristine, prednisone and cytarabine-based chemotherapy combined with vemurafenib improved the prognosis of childhood LCH. In future, prospective clinical trials and novel therapeutic strategies should be developed to improve outcomes in paediatric patients with LCH. KEY MESSAGE Children with Langerhans cell histiocytosis in China present highly heterogeneous clinical characteristics, with up to 60% of cases harbouring mutations in MAPK pathway. Treatment response at 12-week is associated with EFS in our study. Vincristine, prednisone and cytarabine-based chemotherapy combined with vemurafenib improved the prognosis of Chinese childhood LCH, but the reactivation rate is still high.

The role of eosinophils in necrosis mainly in single-system Langerhans cell histiocytosis

Introduction Langerhans cell histiocytosis (LCH) integrates eosinophilic granuloma, Hand-Schüller-Christian disease, and Letterer- Siwe disease due to the proliferation of histiocyte-like cells, which have now been proved to be Langerhans cells [1,2]. The BRAF V600E mutation is an important genetic factor in LCH [3], and new terminology (inflammatory myeloid neoplasia) was introduced

The Value of BRAF VE1 Immunoexpression in Pediatric Langerhans Cell Histiocytosis

Introduction VE1 is a monoclonal antibody detecting mutant BRAF V600E protein by immunohistochemistry (IHC) with a high concordance rate with molecular analysis in many cancers. Materials and methods: BRAF V600E mutation was assessed on 94 pediatric LCH patients using sequencing analysis and VE1 immunohistochemistry with stringent and lenient-scoring criteria. Results: BRAF V600E mutation exon 15 was detected by sequencing in 47.9% of LCH cases. BRAF V600E mutation rate in multiple-system LCH was 65.2%, significantly higher than in single-system LCH (p = .001). VE1 assays showed 35.6% sensitivity, 75.5% specificity (Stringent criteria), and 91.1% sensitivity, 35.7% specificity (Lenient criteria). Conclusions: The proportion of BRAF V600E mutational status was relatively high and related to high-risk LCH. Molecular assays for BRAF mutation detection are preferred in LCH lesions. VE1 is not ready as an alternative option for LCH BRAF testing.

Bone marrow–derived myeloid progenitors as driver mutation carriers in high- and low-risk Langerhans cell histiocytosis

AbstractLangerhans cell histiocytosis (LCH) is a myeloid neoplasia, driven by sporadic activating mutations in the MAPK pathway. The misguided myeloid dendritic cell (DC) model proposes that high-risk, multisystem, risk-organ–positive (MS-RO+) LCH results from driver mutation in a bone marrow (BM)-resident multipotent hematopoietic progenitor, while low-risk, MS-RO− and single-system LCH would result from driver mutation in a circulating or tissue-resident, DC-committed precursor. We have examined the CD34+c-Kit+Flt3+ myeloid progenitor population as potential mutation carrier in all LCH disease manifestations. This population contains oligopotent progenitors of monocytes (Mo's)/macrophages (MΦs), osteoclasts (OCs), and DCs. CD34+c-Kit+Flt3+ cells from BM of MS-RO+ LCH patients produced Langerhans cell (LC)-like cells in vitro. Both LC-like and DC offspring from this progenitor carried the BRAF mutation, confirming their common origin. In both high- and low-risk LCH patients, CD34+c-Kit+Flt3+ progenitor frequency in blood was higher than in healthy donors. In one MS-RO+ LCH patient, CD34+c-Kit+Flt3+ cell frequency in blood and its BRAF-mutated offspring reported response to chemotherapy. CD34+c-Kit+Flt3+ progenitors from blood of both high- and low-risk LCH patients gave rise to DCs and LC-like cells in vitro, but the driver mutation was not easily detectable, likely due to low frequency of mutated progenitors. Mutant BRAF alleles were found in Mo's /MΦs, DCs, LC-like cells, and/or OC-like cells in lesions and/or Mo and DCs in blood of multiple low-risk patients. We therefore hypothesize that in both high- and low-risk LCH, the driver mutation is present in a BM-resident myeloid progenitor that can be mobilized to the blood.