Cell(s) of Origin of Langerhans Cell Histiocytosis

BRAFV600E induces key features of LCH in iPSCs with cell type-specific phenotypes and drug responses

ABSTRACT

Langerhans cell histiocytosis (LCH) is a clonal hematopoietic disorder defined by tumorous lesions containing CD1a+/CD207+ cells. Two severe complications of LCH are systemic hyperinflammation and progressive neurodegeneration. The scarcity of primary samples and lack of appropriate models limit our mechanistic understanding of LCH pathogenesis and affect patient care. We generated a human in vitro model for LCH using induced pluripotent stem cells (iPSCs) harboring the BRAFV600E mutation, the most common genetic driver of LCH. We show that BRAFV600E/WT iPSCs display myelomonocytic skewing during hematopoiesis and spontaneously differentiate into CD1a+/CD207+ cells that are similar to lesional LCH cells and are derived from a CD14+ progenitor. We show that BRAFV600E modulates the expression of key transcription factors regulating monocytic differentiation and leads to an upregulation of proinflammatory molecules and LCH marker genes early during myeloid differentiation. In vitro drug testing revealed that BRAFV600E-induced transcriptomic changes are reverted upon treatment with mitogen-activated protein kinase (MAPK) pathway inhibitors (MAPKis). Importantly, MAPKis do not affect myeloid progenitors but reduce only the mature CD14+ cell population. Furthermore, iPSC-derived neurons (iNeurons) cocultured with BRAFV600E/WT iPSC-derived microglia-like cells, differentiated from iPSC-derived CD34+ progenitors, exhibit signs of neurodegeneration with neuronal damage and release of neurofilament light chain. In summary, the iPSC-based model described here provides a platform to investigate the effects of BRAFV600E in different hematopoietic cell types and provides a tool to compare and identify novel approaches for the treatment of BRAFV600E-driven diseases.

Synchronous Pulmonary Langerhans Cell Histiocytosis and Multiple Cutaneous Reticulohistiocytomas With a Common BRAF- V600E/D Mutation Driver

ABSTRACT

Histiocytoses constitute a group of heterogeneous disorders characterized by involvement of variable organs by neoplastic macrophage or dendritic cells. They may affect both adults and children with a predilection to the skin, bone, lungs, lymph nodes, and CNS. The coexistence of different types of histiocytoses in the same patient is an extremely rare phenomenon. We describe a very rare case of co-occurring pulmonary Langerhans cell histiocytosis with multiple cutaneous reticulohistiocytomas with a common BRAF- V600E mutation as the driver genetic event in both the lung and skin lesions. The presence of a common BRAF- V600E mutation provides evidence of their clonal relation and contributes to our understanding in the pathogenesis of multiple, co-occurring histiocytic proliferations.

Langerhans Cell Histiocytosis Presenting in an Adult Patient With a Pleural Effusion

Langerhans cell histiocytosis is a rare condition characterized by aberrant function and proliferation of the mononuclear phagocyte system. It can occur across all age ranges. This case report involves an adult female presenting with multisystem involvement and pleural effusion. A hypothesis suggests that chronic inflammatory states, resulting from cytokine production and the release of proinflammatory factors, alter vascular permeability, potentially leading to clinical manifestations such as fluid distribution abnormalities, including pleural effusion. Symptomatic multisystemic disease requires chemotherapy initiation. In this case, treatment could not be started due to unresolved empyema despite surgical intervention.

Mechanism of neurodegeneration mediated by clonal inflammatory microglia

Langerhans cell Histiocytosis (LCH) and Erdheim-Chester disease (ECD) are clonal myeloid disorders, associated with MAP-Kinase activating mutations and an increased risk of neurodegeneration. Surprisingly, we found pervasive PU.1+ microglia mutant clones across the brain of LCH and ECD patients with and without neurological symptoms, associated with microgliosis, reactive astrocytosis, and neuronal loss. The disease predominated in the grey nuclei of the rhombencephalon, a topography attributable to a local proliferative advantage of mutant microglia. Presence of clinical symptoms was associated with a longer evolution of the disease and a larger size of PU.1+ clones (p= 0.0003). Genetic lineage tracing of PU.1+ clones suggest a resident macrophage lineage or a bone marrow precursor origin depending on patients. Finally, a CSF1R-inhibitor depleted mutant microglia and limited neuronal loss in mice suggesting an alternative to MAPK inhibitors. These studies characterize a progressive neurodegenerative disease, caused by clonal proliferation of inflammatory microglia (CPIM), with a decade(s)-long preclinical stage of incipient disease that represent a therapeutic window for prevention of neuronal death.

Langerhans cell histiocytosis in sphenoid sinus with vision impairment: Case report and literature review

Langerhans cell histiocytosis (LCH) is a neoplastic disease characterized by aberrant proliferation of the mononuclear phagocyte system, predominantly affecting children under the age of 3 years. Although LCH can affect almost all organs, sinus involvement is rare. This case report documents a 9-year-old boy presented with vision impairment and intermittent headache on the right side. The CT scan and MRI examination revealed the presence of a soft mass in the right atrium of sphenoid sinus, which impacted the right optic canal. Biopsy results confirmed the presence of LCH. Considering the involvement of optic canal and vision impairment, meticulous debridement was performed followed by a 12-month standard chemotherapy. After 2 years of follow-up, the patient showed significant improvement, despite the presence of an encapsulated cyst in the right sphenoid sinus. This case highlights the importance of considering LCH when encountering an isolated soft mass accompanied by decreased vision in the sphenoid sinus. A thorough physical examination, laboratory tests, and imaging methods should be performed, with a biopsy being necessary to confirm the type of lesion and guide the appropriate treatment.

Xanthogranuloma in the External Auditory Canal in Childhood, an Unexpected Lesion

Pedunculated lesions in the external auditory canal present a broad differential diagnosis. It is crucial to rule out malignant neoplasms and consider the possibility of xanthogranulomas, which are very rare in this location. Management is determined by associated complications, and otolaryngologists must consider this for appropriate treatment.

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.

Vitamin E (α-Tocopherol) Does Not Ameliorate the Toxic Effect of Bisphenol S on the Metabolic Analytes and Pancreas Histoarchitecture of Diabetic Rats

This study investigated whether the coadministration of vitamin E (VitE) diminishes the harmful effects provoked by plasticizer bisphenol S (BPS) in the serum metabolites related to hepatic and renal metabolism, as well as the endocrine pancreatic function in diabetic male Wistar rats. Rats were divided into five groups (n = 5-6); the first group was healthy rats (Ctrl group). The other four groups were diabetic rats induced with 45 mg/kg bw of streptozotocin: Ctrl-D (diabetic control); VitE-D (100 mg/kg bw/d of VitE); BPS-D (100 mg/kg bw/d of BPS); The animals from the VitE + BPS-D group were administered 100 mg/kg bw/d of VitE + 100 mg/kg bw/d of BPS. All compounds were administered orally for 30 days. Body weight, biochemical assays, urinalysis, glucose tolerance test, pancreas histopathology, proximate chemical analysis in feces, and the activity of antioxidants in rat serum were assessed. The coadministration of VitE + BPS produced weight losses, increases in 14 serum analytes, and degeneration in the pancreas. Therefore, the VitE + BPS coadministration did not have a protective effect versus the harmful impact of BPS or the diabetic metabolic state; on the contrary, it partially aggravated the damage produced by the BPS. VitE is likely to have an additive effect on the toxicity of BPS.

Central Nervous System Xanthoma Disseminatum: Response to 2CdA in an Adolescent

Xanthoma disseminatum is a normolipemic non-Langerhans cell histiocytosis characterized by red-brown rubbery papules of the skin which coalesce into plaque-like lesions with symmetric involvement of face, flexor, and intertriginous areas. Less commonly, xanthoma disseminatum may affect mucosal linings, abdominal organs, and the central nervous system, leading to endocrinopathies. We report a 12-year-old adolescent with mucosal, central nervous system, and painful cutaneous lesions, further complicated by diabetes insipidus and amenorrhea. Treatment with 2-chlorodeoxyadenosine led to relief of pain and significant improvement of mucosal, central nervous system, and cutaneous lesions, with subsequent restoration of menstrual cycles.

What is the Role of Different Macrophage Subsets in the Evolution of Juvenile Xanthogranulomas?

There are several activated forms of macrophages: 2 main groups are designated M1 and M2. While M1 macrophages have proinflammatory, bactericidal, and phagocytic functions and are the dominant phenotype observed in the early stages of inflammation, M2 macrophages are involved in constructive processes such as tissue repair; they play a role in wound healing and are required for revascularization and re-epithelialization. Juvenile xanthogranuloma (JXG) is the most common non-Langerhans cell histiocytosis. Its pathogenesis is not well understood, but it is not considered a neoplastic entity. JXGs possibly appear as a reaction to a nonspecific injury such as trauma or viral infection, although a genetic predisposition has been suggested in some cases. Tissue damage leads to a histiocytic response. JXGs appear, evolve toward maturation, and then most of them spontaneously regress. Young JXGs are characterized by small macrophages scattered in the dermis, in apposition close to the epidermis. As the lesion matures, the number of foamy macrophages and Touton cells increases and other cell types such as plasma cells, lymphocytes, and polymorphs are observed. Regressing xanthogranulomas will show numerous spindle cells in Significant values are in bold.a storiform distribution, interstitial fibrosis, and few foamy and Touton cells. In this study, we studied the immunophenotypic profile of macrophages found in cutaneous JXGs according to their stage of maturation. We examined the skin biopsies from 25 patients; all were embedded in paraffin and stained with hematoxylin and eosin and for immunohistochemistry. Typically, all JXGs were positive for factor XIIIa and CD4, and were negative for CD1a. The following histiocyte markers were used: CD68, CD204, CD163, MAC387, and HAM56. Images were analyzed by Image J software; data were statistically evaluated by SAS 9.0 software. The cases showed a slight predominance of males and the preference of the JXGs for the axial skin. Lesions occupied the papillary and reticular dermis in 85% of the cases and extended to the subcutaneous fat in the remainder. Compared with mature and regressing JXGs, younger lesions had a higher density of M1 macrophages, stained with MAC387. This antibody labels the histiocytes that have recently arrived in the areas of inflammation. As the lesions matured, there was an overwhelming predominance of M2 macrophages. These cells tended to cluster against the epidermis, except in the 2 cases in phase of regression. This suggests that there is a cross-talk between the epidermis and macrophages and that receptors, cytokines, chemokines, and adhesion molecules may play a role in the development and evolution of JXGs. These results indicate that, for most of their life, JXGs are formed by repairing M2 macrophages and are not just an M1 macrophagic response to a local antigen. The process appears to be influenced by chemical-mediator epidermal-macrophage cross-talking, considering the tendency of these cells to accumulate against the dermoepidermal junction.

Neutralizing Anti-IL-17A Antibody Demonstrates Preclinical Activity Enhanced by Vinblastine in Langerhans Cell Histiocytosis

Langerhans cell histiocytosis (LCH) is an inflammatory myeloid neoplasm characterised by the accumulation into granulomas of apoptosis-resistant pathological dendritic cells (LCH-DCs). LCH outcome ranges from self-resolving to fatal. Having previously shown that, (i) monocyte-derived DCs (Mo-DCs) from LCH patients differentiate into abnormal and pro-inflammatory IL-17A-producing DCs, and (ii) recombinant IL-17A induces survival and chemoresistance of healthy Mo-DCs, we investigated the link between IL-17A and resistance to apoptosis of LCH-DCs. In LCH granulomas, we uncovered the strong expression of BCL2A1 (alias BFL1), an anti-apoptotic BCL2 family member. In vitro, intracellular IL-17A expression was correlated with BCL2A1 expression and survival of Mo-DCs from LCH patients. Based on the chemotherapeutic drugs routinely used as first or second line LCH therapy, we treated these cells with vinblastine, or cytarabine and cladribine. Our preclinical results indicate that high doses of these drugs decreased the expression of Mcl-1, the main anti-apoptotic BCL2 family member for myeloid cells, and killed Mo-DCs from LCH patients ex vivo, without affecting BCL2A1 expression. Conversely, neutralizing anti-IL-17A antibodies decreased BCL2A1 expression, the downregulation of which lowered the survival rate of Mo-DCs from LCH patients. Interestingly, the in vitro combination of low-dose vinblastine with neutralizing anti-IL-17A antibodies killed Mo-DCs from LCH patients. In conclusion, we show that BCL2A1 expression induced by IL-17A links the inflammatory environment to the unusual pro-survival gene activation in LCH-DCs. Finally, these preclinical data support that targeting both Mcl-1 and BCL2A1 with low-dose vinblastine and anti-IL-17A biotherapy may represent a synergistic combination for managing recurrent or severe forms of LCH.

Histiocytic Neoplasms, Version 2.2021, NCCN Clinical Practice Guidelines in Oncology

Histiocytic neoplasms are rare hematologic disorders accounting for less than 1% of cancers of the soft tissue and lymph nodes. Clinical presentation and prognosis of these disorders can be highly variable, leading to challenges for diagnosis and optimal management of these patients. Treatment often consists of systemic therapy, and recent studies support use of targeted therapies for patients with these disorders. Observation ("watch and wait") may be sufficient for select patients with mild disease. These NCCN Guidelines for Histiocytic Neoplasms include recommendations for diagnosis and treatment of adults with the most common histiocytic disorders: Langerhans cell histiocytosis, Erdheim-Chester disease, and Rosai-Dorfman disease.

Langerhans cell histiocytosis in adults: a retrospective, single-center case series

Langerhans cell histiocytosis is rare in adults, and most of what we know about its diagnosis and treatment comes from pediatric studies. We report clinical findings and results of treatment in a retrospective series of 63 consecutive adult patients (18-76 years old), treated at our pediatric unit from 1990 to 2020 using the same approach as for children. Patients were classified as having single-system disease (SS-LCH) in 41 cases, which was unifocal in 34 of them and multifocal in 7, or multisystem disease (MS-LCH) in 17 and primary pulmonary (pLCH) in 5. Twenty patients also had diabetes insipidus. A "wait and see" strategy was recommended after biopsy/surgery for patients with unifocal SS-LCH. Systemic treatment was proposed for cases of SS-LCH involving "special sites" or with multifocal disease, and in cases of MS-LCH. EFS and OS for the cohort as a whole were 62.2% and 100%, respectively, at 5 years and 52.5% and 97.6% at 10 years. Three patients died due to the damage caused by the multiple therapies administered. The rate of disease reactivation was high (affecting 40% of cases), with several reactivations over the years despite multiple lines of treatment. Though clinical history of LCH may differ between adults and children, in the absence of specific, tailored protocols, clinical approach to adult cases may draw on pediatric experience. Patients with limited disease have a good prognosis without any need for systemic therapy. Potentially greater toxicity in adults of systemic treatments generally used in pediatric setting should be borne in mind.

Pulmonary Manifestations of GATA2 Deficiency

BACKGROUND

GATA2 deficiency is a genetic disorder of hematopoiesis, lymphatics, and immunity caused by autosomal dominant or sporadic mutations in GATA2. The disease has a broad phenotype encompassing immunodeficiency, myelodysplasia, leukemia, and vascular or lymphatic dysfunction as well as prominent pulmonary manifestations.

RESEARCH QUESTION

What are the pulmonary manifestations of GATA2 deficiency?

STUDY DESIGN AND METHODS

A retrospective review was conducted of clinical medical records, diagnostic imaging, pulmonary pathologic specimens, and tests of pulmonary function.

RESULTS

Of 124 patients (95 probands and 29 ascertained), the lung was affected in 56%. In addition to chronic infections, pulmonary alveolar proteinosis (11 probands) and pulmonary arterial hypertension (nine probands) were present. Thoracic CT imaging found small nodules in 54% (54 probands and 12 relatives), reticular infiltrates in 40% (45 probands and four relatives), paraseptal emphysema in 25% (30 probands and one relative), ground-glass opacities in 35% (41 probands and two relatives), consolidation in 21% (23 probands and two relatives), and a typical crazy-paving pattern in 7% (eight probands and no relatives). Nontuberculous mycobacteria were the most frequent organisms associated with chronic infection. Allogeneic hematopoietic stem cell transplantation successfully reversed myelodysplasia and immune deficiency and also improved pulmonary hypertension and pulmonary alveolar proteinosis in most patients.

INTERPRETATION

GATA2 deficiency has prominent pulmonary manifestations. These clinical observations confirm the essential role of hematopoietic cells in many aspects of pulmonary function, including infections, alveolar proteinosis, and pulmonary hypertension, many of which precede the formal diagnosis, and many of which respond to stem cell transplantation.

Histiocytosis and the nervous system: from diagnosis to targeted therapies

Histiocytoses are heterogeneous hematopoietic diseases characterized by the accumulation of CD68(+) cells with various admixed inflammatory infiltrates. The identification of the pivotal role of the mitogen-activated protein kinase (MAPK) pathway has opened new avenues of research and therapeutic approaches. We review the neurologic manifestations of 3 histiocytic disorders with frequent involvement of the brain and spine: Langerhans cell histiocytosis (LCH), Erdheim-Chester disease (ECD), and Rosai-Dorfman-Destombes disease (RDD). Central nervous system (CNS) manifestations occur in 10%-25% of LCH cases, with both tumorous or neurodegenerative forms. These subtypes differ by clinical and radiological presentation, pathogenesis, and prognosis. Tumorous or degenerative neurologic involvement occurs in 30%-40% of ECD patients and affects the hypothalamic-pituitary axis, meninges, and brain parenchyma. RDD lesions are typically tumorous with meningeal or parenchymal masses with strong contrast enhancement. Unlike LCH and ECD, neurodegenerative lesions or syndromes have not been described with RDD. Familiarity with principles of evaluation and treatment both shared among and distinct to each of these 3 diseases is critical for effective management. Refractory or disabling neurohistiocytic involvement should prompt the consideration for use of targeted kinase inhibitor therapies.

Oncogene-induced senescence in hematopoietic progenitors features myeloid restricted hematopoiesis, chronic inflammation and histiocytosis

Activating mutations in the BRAF-MAPK pathway have been reported in histiocytoses, hematological inflammatory neoplasms characterized by multi-organ dissemination of pro-inflammatory myeloid cells. Here, we generate a humanized mouse model of transplantation of human hematopoietic stem and progenitor cells (HSPCs) expressing the activated form of BRAF (BRAF^V600E). All mice transplanted with BRAF^V600E-expressing HSPCs succumb to bone marrow failure, displaying myeloid-restricted hematopoiesis and multi-organ dissemination of aberrant mononuclear phagocytes. At the basis of this aggressive phenotype, we uncover the engagement of a senescence program, characterized by DNA damage response activation and a senescence-associated secretory phenotype, which affects also non-mutated bystander cells. Mechanistically, we identify TNFα as a key determinant of paracrine senescence and myeloid-restricted hematopoiesis and show that its inhibition dampens inflammation, delays disease onset and rescues hematopoietic defects in bystander cells. Our work establishes that senescence in the human hematopoietic system links oncogene-activation to the systemic inflammation observed in histiocytic neoplasms.

High prevalence of BRAFV600E in patients with cholestasis, sclerosing cholangitis or liver fibrosis secondary to Langerhans cell histiocytosis

Targeted therapies with MAPK inhibitors have proven to modulate the clinical manifestations of patients with Langerhans cell histiocytosis (LCH). We explored the presence of BRAF^V600E mutation in our cohort of patients with LCH and cholestasis, sclerosing cholangitis, or liver fibrosis that presented resistance to chemotherapy. The BRAF^V600E mutation was detected either in the diagnosis (skin and bone) or liver biopsy in our cohort of 13 patients. Thus, we observed a high incidence of BRAF^V600E mutation in 100% either in diagnostic biopsy (skin and bone) or liver biopsy in patients with progressive liver disease, sequela, or liver transplant requirement.

Brain Somatic Mutation in Aging and Alzheimer's Disease

Somatic mutations arise postzygotically, producing genetic differences between cells in an organism. Well established as a driver of cancer, somatic mutations also exist in nonneoplastic cells, including in the brain. Technological advances in nucleic acid sequencing have enabled recent break-throughs that illuminate the roles of somatic mutations in aging and degenerative diseases of the brain. Somatic mutations accumulate during aging in human neurons, a process termed genosenium. A number of recent studies have examined somatic mutations in Alzheimer’s disease (AD), primarily from the perspective of genes causing familial AD. We have also gained new information on genome-wide mutations, providing insights into the cellular events driving somatic mutation and cellular dysfunction. This review highlights recent concepts, methods, and findings in the progress to understand the role of brain somatic mutation in aging and AD.

Recent advances in the understanding of the molecular pathogenesis and targeted therapy options in Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is the most common histiocytic disorder caused by the clonal expansion of myeloid precursors that differentiate into CD1a+/CD207+ cells in the lesion. Advances in genomic sequencing techniques have improved our understanding of the pathophysiology of LCH. Activation of the mitogen-activated protein kinase (MAPK) pathway is a key molecular mechanism involved in the development of LCH. Recurrent BRAF mutations and MAP2K1 mutations are the major molecular alterations involved in the activation of the MAPK pathway. Recent studies have supported the “misguided myeloid differentiation model” of LCH, where the extent of disease is defined by the differentiation stage of the cell in which the activating somatic MAPK mutation occurs, suggesting LCH. Several studies have advocated the efficacy of targeted therapy using BRAF inhibitors with a high response rate, especially in patients with high-risk or refractory LCH. However, the optimal treatment scheme for children remains unclear. This review outlines recent advances in LCH, focusing on understanding the molecular pathophysiology, emerging targeted therapy options, and their clinical implications.

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

Langerhans 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.

Periodontal manifestations of Langerhans cell histiocytosis: a systematic review

Objectives

To explore the evidence of periodontal manifestations and treatment modalities in patients with Langerhans cell histiocytosis (LCH).

Material and methods

A systematic literature search was performed and the criteria for PRISMA and risk of bias assessment were applied. Human clinical studies (≥10 patients) presenting patients with LCH and periodontal findings were considered for inclusion.

Results

From 298 titles identified, six case series with a total of 1278 patients suffering from LCH were included. In these studies, oral symptoms were reported in a frequency ranging from 10 to 100%. Overall, in 216 patients (17%), oral symptoms were observed. Out of these patients, 49–100% demonstrated periodontal symptoms. The most common oral findings were pain, swelling, tooth loss/mobility, and bone lesions. Specific periodontal findings comprised varying frequencies of gingival ulcerations, increased pocket depths, and gingival bleeding. Treatment measures constituted of surgical curettage of bone lesions, soft tissue excision and/or tooth extractions, radiotherapy, systemic chemotherapy, or a combination of these approaches. Healing without recurrence of oral lesions was reported in most of the cases.

Conclusions

The available evidence on periodontal manifestations in LCH patients is heterogeneous. Several oral and periodontal findings were reported and may occur as initial symptoms and/or at later stages of the disease.

Clinical relevance

The dentist should be aware of possible oral involvement of systemic diseases such as LCH, and these manifestations may mimic periodontal disease.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00784-021-03873-0.

Eosinophilic Granuloma of the Skull Presenting as Non-Traumatic Extradural Haematoma in Children

Cranial extradural haematoma (EDH) is a neurosurgical emergency that can be caused by traumatic or non-traumatic causes with the former being more prevalent. Non-traumatic causes are variable and can include infection, vascular malformation and haematological disorders. This paper will address an extremely rare non-traumatic cause of EDH. More specifically, eosinophilic granuloma (EG), the localized form of Langerhans histiocytosis, may involve the skull and has rarely been reported to present with EDH. The case that will be presented is that of a three-year-old male patient, who presented with progressive vomiting and drowsiness, associated with left parietal swelling. CT scan of the brain showed an extradural haematoma and an osteolytic parietal lesion. He underwent emergent craniectomy, evacuation of the haematoma and dura resection as the lesion was infiltrating the dura. Histopathological examination of the dura and the bone edges showed eosinophilic granuloma (EG). The mechanism of a haemorrhage in this situation is poorly understood and the literature is extremely scarce. In conducting a thorough literature review, only 11 case reports of EG causing non-traumatic EDH were found. The details of these 11 cases will be reviewed and discussed in this paper, in addition to our illustrative case.

Chest computed tomography findings for a cohort of children with pulmonary Langerhans cell histiocytosis

OBJECTIVE

This study was undertaken to describe the spectrum of lung computed-tomography (CT) findings in children with pulmonary Langerhans cell histiocytosis (PLCH) and to evaluate for this population the CT-scan nodule and cyst scores proposed by adult pulmonologists at diagnosis and during follow-up.

METHODS

Among 175 children with PLCH identified in the French national population-based Langerhans cell histiocytosis cohort, 60 were retrospectively selected by the availability of CT for a central review by three pediatric radiologists. These 60 patients are representative of childhood PLCH for almost all clinical aspects, except a lower percentage of risk organ involvement (38% vs 54%; P = 0.05).

RESULTS

The 60 children's chest CT scans (n = 218) were reviewed. At diagnosis, 63% of them had nodules, 53% had cysts, and 29% had both. The percentages of patients with nodules or cysts increased from diagnosis to peak disease activity, respectively, from 63% to 73% and from 53% to 66%. The costophrenic angle was involved in 71%. Patients with pneumothorax (25%) had a higher median cyst score. Alveolar consolidation was observed in 34%. Patients with low CT-scan nodule and cyst scores had no long-term pulmonary sequelae.

CONCLUSIONS

Well-known characteristics of adult PLCH (nodules and cysts) were observed in children. The chest CT scores proposed by adult pulmonologists could easily be applied to childhood PLCH. Lesions in children, unlike those in adults, are frequently located near the costophrenic angles. Alveolar consolidation might be considered an atypical feature of childhood PLCH.

Osteopontin is highly secreted in the cerebrospinal fluid of patient with posterior pituitary involvement in Langerhans cell histiocytosis

BACKGROUND

Langerhans cell histiocytosis (LCH) is a rare disease caused by clonal proliferation of CD1a⁺ CD207⁺ cells. Distinguishing pituitary involvement was essential in stratification and treatment of patients with LCH. The diagnosis of pituitary involvement is mainly dependent on hormone abnormalities in the anterior pituitary and magnetic resonance imaging (MRI) scanning in posterior pituitary. Diabetes insipidus (DI) is a serious sequelae and often occurred with pituitary involvement. It is reported that osteopontin (OPN) is highly secreted in the cerebrospinal fluid (CSF) of patients with neurodegenerative diseases in LCH (LCH-ND). However, patients with posterior pituitary involvement account for a larger portion in our hospital. Whether the OPN level could be an auxiliary diagnostic marker for the posterior pituitary involvement or not is still unknown.

METHODS

In our study, we collected CSF samples of 57 children with LCH. The secreted OPN (sOPN) levels in CSF were measured through enzyme-linked immunosorbent assay (ELISA).

RESULTS

After the retrospective analysis of 57 patients with LCH, we found that the sOPN levels in CSF of children with posterior pituitary involvement were significantly higher than that of other groups. After the Pearson Chi-Square test, Fisher's exact test and ROC analysis, we found that the sOPN levels were significantly correlated with posterior pituitary involvement. The cut-off value is 214.14 ng/mL.

CONCLUSION

The sOPN levels were elevated in CSF of LCH children with posterior pituitary involvement. Analysis of the sOPN level may provide more accurate auxiliary diagnostic techniques for the clinic.

Immunohistochemical characterization of immune cell infiltration in paediatric and adult Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is an inflammatory myeloid neoplasia commonly affecting children with frequent somatic mutations in MAPK pathway genes including BRAF^V600E and MAP2K1. Some studies suggest that LCH cells can recruit and modulate inflammatory cells, which could provide reciprocal survival signals. To characterize the immune profile of infiltrating inflammatory cells, and to clarify their participation in LCH pathogenesis, a detailed immunohistochemical analysis was performed. Fifteen (10 children, 5 adults) LCH cases were assessed through macrophage (CD68 and CD163), mature dendritic cell (mDC; CD83 and CD208), regulatory T cell (Treg; CD4, CD25 and FOXP3) and cytotoxic lymphocyte (CL; CD56, CD57, perforin and granzyme B) immunomarkers. Moreover, lymphocytic and LCH markers were also analysed. All cases were S100, CD1a, CD207 and CD4-positive. Bcl-2 and cyclin D1 expression was observed in 13 of 15 cases. In the immune microenvironment, M2-polarized macrophages and Tregs were the predominant cell populations, followed by significantly (P < .005) smaller levels of mDCs and CLs. Additionally, the number of CD3 + cells was significantly higher than that of CD20 + cells. In the CD3 + cell population, there were a significantly higher number of CD4 + cells than CD8 + cells. While there were no differences when comparing the paediatric and adult populations, FOXP3 + cells were significantly higher in patients with multisystem involvement and treated with chemotherapy, than single-site cases and those without chemotherapy. Our results suggest that M2-polarized macrophages and Treg infiltration can promote LCH development and survival, probably through pro-tumoral, immunosuppressive and/or cytokine-mediated mechanisms. This work highlights the need for further exploration of immune-targeted therapy for LCH.

Juvenile Xanthogranuloma: An Entity With a Wide Clinical Spectrum

Juvenile xanthogranulomas (JXGs) are rare, benign lesions that belong to the large group of non-Langerhans cell histiocytoses. JXG presents with 1 or more erythematous or yellowish nodules that are usually located on the head or neck. Most JXG lesions are congenital or appear during the first year of life. Extracutaneous involvement is rare, but the literature traditionally suggests investigating the possibility of ocular compromise. JXG is mainly a clinical diagnosis, but a skin biopsy may sometimes be needed for confirmation. JXGs on the skin are self-limiting and usually do not require treatment. This review describes the clinical and therapeutic aspects of JXG, emphasizing available evidence and the diagnosis of extracutaneous involvement.

BRAF-V600E-mutated Rosai-Dorfman-Destombes disease and Langerhans cell histiocytosis with response to BRAF inhibitor

Demonstration of BRAF-V600E in Rosai-Dorfman-Destombes disease requires sensitive molecular assays and molecular-based tissue immunostain. BRAF-V600E blood testing is important for disease-monitoring BRAF-mutated histiocytosis and can guide inhibitor treatment plans.

Multisystemic Pediatric Langerhans cell histiocytosis: a comprehensive clinico-pathological and BRAF V600E mutation study at autopsy

Langerhans cell histiocytosis (LCH), a disorder of antigen-presenting cells, is the commonest disorder of the mononuclear phagocytic system. Diagnosis is always challenging due to heterogeneous clinical presentation. However, with the evolution and better understanding of its biology, many of these children are being diagnosed early and offered appropriate therapy. Despite these advances, in developing countries, an early diagnosis is still challenging due to resource constraints for specialized tests. As a result, many patients succumb to their disease. Autopsy data on LCH is notably lacking in the literature. We sought to analyze the clinical (including mutational) and morphologic features at autopsy in six proven cases of LCH. This study includes a detailed clinico-pathological and mutational analysis of 6 proven cases of LCH. Presence of BRAF V600E mutation was assessed by both Real Time PCR and Sanger sequencing. A varied spectrum of organ involvement was noted with some rare and novel morphological findings, like nodular bronchiolocentric infiltration of LCH cells, lymphovascular emboli of LCH cells, and paucity of eosinophils within the infiltrate; these features have not been described earlier. Surprisingly, all cases were negative for BRAF V600E mutation on both RQ-PCR and Sanger sequencing. The present study is perhaps the first autopsy series on LCH. This extensive autopsy analysis represents a correlation of pathological features with clinical symptoms which provides clues for a timely diagnosis and appropriate therapeutic intervention. Also, our findings hint at the low frequency of BRAF V600E mutation in our LCH patients.

[Giant cell tumor of bone : Morphology, molecular pathogenesis, and differential diagnosis]

The histological picture of giant cell tumor of bone is characterized by numerous osteoclast-like giant cells. However, these are not the actual tumor cells, but constitute a reactive infiltrate. Rather, the tumor cells are mononuclear mesenchymal cells, which even reveal an osteoblastic line of differentiation. The CD68-positive macrophages form the second group of mononuclear cells. The receptor activator of nuclear factor kappa-B/ligand (RANK/RANKL) system, which belongs to the tumor necrosis factor (TNF) cytokine family, is decisively involved in the activation of the giant cells. It is generally accepted that a RANKL expression of mononuclear stromal cells is responsible for the development and differentiation of osteoclast-like giant cells. Therefore, the RANKL inhibitor denosumab constituted an essential element for giant cell tumor therapy over the last several years, as it blocks the maturation of osteoclasts and thus the osteolytic activity and the spread of tumor. However, with time it became evident that the not risk-free therapy with denosumab may lead to extensive recurrences upon withdrawal, so this therapy is applied with caution today.At the molecular genetic level, the giant cell tumors of bone are characterized by point mutations in the H3F3A gene. The detection of this mutation is used for the diagnostic differentiation from other bone lesions containing giant cells. Giant cell osteosarcomas rarely contain H3F3A mutations. Chondroblastoma is characterized by mutations in the H3F3B gene.

Circulating CD1c+ myeloid dendritic cells are potential precursors to LCH lesion CD1a+CD207+ cells

Langerhans cell histiocytosis (LCH) is a myeloproliferative disorder that is characterized by the inflammatory lesions with pathogenic CD1a+CD207+ dendritic cells (DCs). BRAFV600E and other somatic activating MAPK gene mutations have been identified in differentiating bone marrow and blood myeloid cells, but the origin of the LCH lesion CD1a+CD207+ DCs and mechanisms of lesion formation remain incompletely defined. To identify candidate LCH CD1a+CD207+ DC precursor populations, gene-expression profiles of LCH lesion CD1a+CD207+ DCs were first compared with established gene signatures from human myeloid cell subpopulations. Interestingly, the CD1c+ myeloid DC (mDC) gene signature was most enriched in the LCH CD1a+CD207+ DC transcriptome. Additionally, the BRAFV600E allele was not only localized to CD1a+CD207- DCs and CD1a+CD207+ DCs, but it was also identified in CD1c+ mDCs in LCH lesions. Transcriptomes of CD1a+CD207- DCs were nearly indistinguishable from CD1a+CD207+ DCs (both CD1a+CD207low and CD1a+CD207high subpopulations). Transcription profiles of LCH lesion CD1a+CD207+ DCs and peripheral blood CD1c+ mDCs from healthy donors were compared to identify potential LCH DC-specific biomarkers: HLA-DQB2 expression was significantly increased in LCH lesion CD1a+CD207+ DCs compared with circulating CD1c+ mDCs from healthy donors. HLA-DQB2 antigen was identified on LCH lesion CD1a+CD207- DCs and CD1a+CD207+ DCs as well as on CD1c+(CD1a+CD207-) mDCs, but it was not identified in any other lesion myeloid subpopulations. HLA-DQB2 expression was specific to peripheral blood of patients with BRAFV600E+ peripheral blood mononuclear cells, and HLA-DQB2+CD1c+ blood cells were highly enriched for the BRAFV600E in these patients. These data support a model in which blood CD1c+HLA-DQB2+ mDCs with activated ERK migrate to lesion sites where they differentiate into pathogenic CD1a+CD207+ DCs.

Pituitary Stalk Enlargement in Adults

Pathologies involving the pituitary stalk (PS) are generally revealed by the presence of diabetes insipidus. The availability of MRI provides a major diagnostic contribution by enabling the visualization of the site of the culprit lesion, especially when it is small. However, when only an enlarged PS is found, the etiological workup may be difficult, particularly because the biopsy of the stalk is difficult, harmful and often not contributive. The pathological proof of the etiology thus needs to be obtained indirectly. The aim of this article was to provide an accurate review of the literature about PS enlargement in adults describing the differences between the numerous etiologies involved and consequent different diagnostic approaches. The etiological diagnostic procedure begins with the search for possible other lesions suggestive of histiocytosis, sarcoidosis, tuberculosis or other etiologies elsewhere in the body that could be more easily biopsied. We usually perform neck, thorax, abdomen, and pelvis CT scan; positron emission tomography scan; bone scan; or other imaging methods when we suspect generalized lesions. Measurement of serum markers such as human chorionic gonadotropin, alpha-fetoprotein, angiotensin converting enzyme, and IgG4 may also be helpful. Obviously, in the presence of an underlying carcinoma (particularly breast or bronchopulmonary), one must first consider a metastasis located in the PS. In the case of an isolated PS enlargement, simple monitoring, without histological proof, can be proposed (by repeating MRI at 3-6 months) with the hypothesis of a germinoma (particularly in a teenager or a young adult) that, by increasing in size, necessitates a biopsy. In contrast, a spontaneous diminution of the lesion is suggestive of infundibulo-neurohypophysitis. We prefer not to initiate steroid therapy to monitor the spontaneous course when a watch-and-see attitude is preferred. However, in many cases, the etiological diagnosis remains uncertain, requiring either close monitoring of the lesion or, in exceptional situations, trying to obtain definitive pathological evidence by a biopsy, which, unfortunately, is in most cases performed by the transcranial route. If a simple surveillance is chosen, it has to be very prolonged (annual surveillance). Indeed, progression of histiocytosis or germinoma may be delayed.

Vemurafenib for Refractory Multisystem Langerhans Cell Histiocytosis in Children: An International Observational Study

PURPOSE

Off-label use of vemurafenib (VMF) to treat BRAFV600E mutation-positive, refractory, childhood Langerhans cell histiocytosis (LCH) was evaluated.

PATIENTS AND METHODS

Fifty-four patients from 12 countries took VMF 20 mg/kg/d. They were classified according to risk organ involvement: liver, spleen, and/or blood cytopenia. The main evaluation criteria were adverse events (Common Terminology Criteria for Adverse Events [version 4.3]) and therapeutic responses according to Disease Activity Score.

RESULTS

LCH extent was distributed as follows: 44 with positive and 10 with negative risk organ involvement. Median age at diagnosis was 0.9 years (range, 0.1 to 6.5 years). Median age at VMF initiation was 1.8 years (range, 0.18 to 14 years), with a median follow-up of 22 months (range, 4.3 to 57 months), whereas median treatment duration was 13.9 months (for 855 patient-months). At 8 weeks, 38 complete responses and 16 partial responses had been achieved, with the median Disease Activity Score decreasing from 7 at diagnosis to 0 (P < .001). Skin rash, the most frequent adverse event, affected 74% of patients. No secondary skin cancer was observed. Therapeutic plasma VMF concentrations (range, 10 to 20 mg/L) seemed to be safe and effective. VMF discontinuation for 30 patients led to 24 LCH reactivations. The blood BRAFV600E allele load, assessed as circulating cell-free DNA, decreased after starting VMF but remained positive (median, 3.6% at diagnosis, and 1.6% during VMF treatment; P < .001) and was associated with a higher risk of reactivation at VMF discontinuation. None of the various empirical therapies (hematopoietic stem-cell transplantation, cladribine and cytarabine, anti-MEK agent, vinblastine, etc) used for maintenance could eradicate the BRAFV600E clone.

CONCLUSION

VMF seemed safe and effective in children with refractory BRAFV600E-positive LCH. Additional studies are needed to find effective maintenance therapy approaches.

Clonal evolution of chronic lymphocytic leukemia to Langerhans cell histiocytosis: a case report

The traditional concept of unidirectional maturation of hematopoietic cells has been called into question due to the recognition of lineage plasticity, which is increasingly found also in the clonal evolution of hematopoietic and lymphoid malignancies. Here we present an unusual case of a patient with TP53-mutated chronic lymphocytic leukemia (CLL) treated with a PI3Kδ inhibitor evolving to clonally related Langerhans cell histiocytosis (LCH) with acquired BRAF V600E and STK11 mutations and loss of expression of PAX-5 and other examined B cell markers. In indolent B cell lymphoma, transformation to a more aggressive high-grade lymphoma occurs frequently during the course of disease and is thought to be caused by clonal evolution. Our case further supports the concept of significant lineage plasticity in lymphomas and raises the question of a potential role of novel pharmacologic agents in clonal evolution.

Progress towards molecular-based management of childhood Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is characterized by inflammatory lesions containing abundant CD1a+ CD207+ histiocytes that lead to the destruction of affected tissues. This disease has a remarkable pleiotropic clinical presentation and most commonly affects young children. Although the current mortality rate is very low for childhood LCH patients (<2%), reactivation frequently occurs after a long period of disease control and the rates of permanent complications and sequelae remain high. Advances in genomic sequencing technologies in this past decade have highlighted somatic molecular alterations responsible for the disease in around 80% of childhood LCH cases. More than half of these cases harbored the BRAF^V600E mutation, and most other mutations also concerned proteins involved in the MAPKinase pathway. In addition to improving what is known about the LCH pathology, this molecular knowledge provides opportunities to optimize patient management. The BRAF^V600E mutation is associated with more severe presentations of the disease, a high reactivation rate, and a high permanent complication rate; this mutation therefore paves the way for future stratified management approaches. These therapies may be based on the patient's molecular status as well as other clinical characteristics of the disease that are independently associated with undesired events. Moreover, as observed in patients with solid tumors, the BRAF^V600E allele can be detected in the circulating cell-free DNA of patients with severe BRAF^V600E-mutated LCH. Quantification of the plasmatic BRAF^V600E load for this group of patients can precisely monitor response to therapy. Finally, targeted therapies, such as BRAF inhibitors, are new therapeutic options especially designed for refractory multisystemic LCH involving risk organs. However, the long-term efficacy, long-term tolerance, optimal protocol scheme, and appropriate modalities of administration for these innovative therapies for children still need to be defined, a huge challenge.

Systemic Histiocytosis (Langerhans Cell Histiocytosis, Erdheim-Chester Disease, Destombes-Rosai-Dorfman Disease): from Oncogenic Mutations to Inflammatory Disorders

PURPOSE OF REVIEW

Provide an overview of recent progress in decoding the pathogenesis and treatment of systemic histiocytoses.

RECENT FINDINGS

Advances in molecular techniques over the last few years, enabling the identification of several MAPK mutations in lesion histiocytes, have revolutionized our understanding of histiocytosis that led to a revised classification and new treatments. Since the 2010 discovery of the BRAF^V600E mutation in 57% of Langerhans cell histiocytosis (LCH) lesions, several other kinase mutations have been found, mostly in the MAPK pathway, and also in other key signaling pathways, in LCH, Erdheim-Chester Disease (ECD) and, less frequently, Destombes-Rosai-Dorfman disease (RDD). Those revolutionary breakthroughs enhanced our understanding of the pathogenesis of histiocytosis and led to trials with targeted therapies that demonstrated notable efficacy.

Childhood pulmonary Langerhans cell histiocytosis: a comprehensive clinical-histopathological and BRAFV600E mutation study from the French national cohort

Childhood pulmonary Langerhans cell histiocytosis (PLCH) is a rare disease. Its pulmonary histopathology, according to comprehensive clinical-radiological findings and BRAF^V600E mutation status, has not yet been thoroughly documented. From the 167 childhood PLCH cases entered in the French National Histiocytosis Registry (1983-2016), we retrieved lung biopsies from a consecutive retrospective series of 17 patients, diagnosed when they were 2 weeks to 16 years old (median, 9.4 years), and report the clinical and histopathological findings herein. Histological analyses of biopsies (16 surgical and 1 postmortem) found the following features, alone or associated: Langerhans cell (LC) nodules with cavitation (9/17), cysts (14/17), fibrotic scars (2/17), peribronchiolar topographic distribution of the lesions (10/17), and accessory changes, like stretch emphysema (7/17). Those characteristics closely resemble those describing adult PLCH. However, unusual findings observed were 2 large nodules and a diffuse interstitial LC infiltrate. BRAF^V600E mutation was detected in 4 of 12 samples tested, notably in the 3 with unusual features. In conclusion, childhood PLCH mostly shares the common histology features already described in adult PLCH, regardless of age. Because smoking is considered the major trigger in PLCH pathogenesis, the findings based on this series suggest other inducers of bronchiolar LC recruitment, especially in very young patients.

[Multisystem histiocytosis of Langerhans cells associated with Lymphomatoid papulosis: An accidental finding? Case report and literature review]

Langerhans cell histiocytosis (LCH) is a disease characterized by proliferation of CD1a+dendritic cells with local or diffuse organ compromise. The identification of recurrent gene mutations has confirmed the hypothesis of LCH as a true neoplasm. Lymphomatoid papulosis (LyP) belongs to the spectrum of CD30+primary cutaneous lymphomas. LCH has been described in association with other lymphoproliferative disorders. However, lesions constituted by Langerhans cells (LC) have been commonly considered reactive, related to cytokines produced by the lymphoma-microenvironment interaction. Some authors designate these lesions as "Langerhans cells-like lesions". We present the case of a 28-years-old woman with multisystem LCH and simultaneous PyL lesions with reactive LC hyperplasia.

Infiltrating the Heart and Kidney: A Rare Pediatric Case of Multisystem Langerhans Cell Histiocytosis from Pakistan

Langerhans cell histiocytosis (LCH) is a rare, clonal disease of the monocyte-macrophage system, varying in its clinical presentation from mere self-healing skin and bone lesions to life-threatening multi-system disease. In descending order of frequency, the disease is known to involve the skeleton, skin, lymph nodes and lesser often, the liver, spleen, lungs, hematopoietic and central nervous systems. Here, we present a pediatric case of multi-system LCH in a five-year-old child, unique in its evident cardiac and renal involvement alongside other organ systems and important in how the diagnosis was aided by a fine needle aspiration cytology instead of the costlier histopathological procedures, in a setting with limited resources.

Atypical presentation of isolated orbital Langerhans cell histiocytosis

Background

A 9-year old female presented with one month of waxing and waning upper eyelid swelling. An excisional biopsy via anterior orbitotomy was performed.

Objective

To describe a patient presenting atypically with symptoms concerning for orbital cellulitis who was diagnosed with Langerhans cell histiocytosis (LCH).

Methods

Description of case report.

Results

We report a case of a 9-year old female with one month of periorbital edema and erythema suspected to be orbital cellulitis. A complete ophthalmological exam, subsequent imaging, and an excisional biopsy revealed the diagnosis of LCH. With a confirmed diagnosis, the patient started chemotherapy indicated by the Histiocyte Society Evaluation and Treatment Guidelines.

Conclusion

Langerhans cell histiocytosis (LCH) embodies a spectrum of diseases with the primary pathologic process being the abnormal proliferation of polyclonal Langerhans cells. In children with isolated bony involvement, the most common presenting symptom is pain. Rarely is orbital involvement with associated periorbital edema and erythema the primary presentation.

A novel fusion gene PLEKHA6-NTRK3 in langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is the most common histiocytosis with constitutive activation of the RAS-RAF-MEK-ERK (MAPKinase) cell signaling pathway. We analyzed 89 cases of BRAF and MAP2K1 mutations by Sanger sequencing, of which 18 cases showed that these two gene mutations are negative. Whole genome sequencing of suitable specimens in these negative cases revealed a translocation from the 3 intron of PLEKHA6 to the 13 intron of NTRK3 in one case. We identified that this translocation could cause a novel fusion mutation, PLEKHA6-NTRK3. Overexpression of the PLEKHA6-NTRK3 mutant in NIH 3T3 cells enhanced MAPKinase pathway activation, promote cell growth. Our result suggested that a new mutation need be included in LCH molecular screening panel to better define its prevalence in LCH.

Comparison between low-dose chemotherapy and surgery for the treatment of extremity-associated solitary bone lesions in children with Langerhans cell histiocytosis in South China: A case-control study

Background

The treatment algorithm for solitary bone lesions of Langerhans cell histiocytosis (SBL-LCH) in children extremities still remains controversial. We conducted a retrospective case-control study to compare the feasibility of low-dose chemotherapy (LDC) and surgery for SBL-LCH in children extremities.

Patients and methods

This study compares 43 pediatric patients starting LDC with a surgery control group (n = 44), matched for gender, age, follow-up time, and lesion sites and sizes, treated between 2001 and 2015 at our institution. Hospital stay (HS), time to symptom relief (TTSR), recovery time (RT), complications, relapse-free survival (RFS), health-related quality of life (HRQOL) and cost-effectiveness were analyzed for each strategy.

Results

HS, TTSR and RT in the LDC group were shorter than those in the surgery group (p < 0.01). Chemotherapy-related complications included nausea (16.30%), aminotransferase elevation (9.30%), slight hair loss (11.63%), decline in immune function (23.26%), growth retardation (16.30%), and moon face (9.30%). Chemotherapy-related side effects were mild and well tolerated. Pathologic fractures (6.81%), loosening of instrumentation (6.00%,), surgical site infection (4.00%) and rejection of bone grafting (9.09%) developed in surgery patients. LDC treatment resulted in a longer RFS (87 months) than surgery alone (59 months) (p = 0.011). Furthermore, compared with surgery patients, patients in the LDC group had a better HRQOL at 3 months’ follow-up for the physical, role, emotional and social function domains assessed (p < 0.001, p = 0.001, p < 0.001 and p = 0.003, respectively) according to the European Organisation for Research and Treatment of Cancer QLQ-C30® survey. However, HRQOL scores at 2 years’ follow-up were similar between the two groups. The incremental cost-effectiveness ratio (ICER) was ¥−137,030/quality-adjusted life year (QALY) for LDC versus surgery.

Conclusions

Compared with surgery, LDC promotes more rapid recovery, is less invasive, is characterized by increased safety and a superior HRQOL, and is a more cost-effective treatment strategy for pediatric patients with SBL-LCH in the extremities.

Expression of the transcription factor ZBTB46 distinguishes human histiocytic disorders of classical dendritic cell origin

Distinguishing classical dendritic cells from other myeloid cell types is complicated by the shared expression of cell surface markers. ZBTB46 is a zinc finger and BTB domain-containing transcription factor, which is expressed by dendritic cells and committed dendritic cell precursors, but not by plasmacytoid dendritic cells, monocytes, macrophages, or other immune cell populations. In this study, we demonstrate that expression of ZBTB46 identifies human dendritic cell neoplasms. We examined ZBTB46 expression in a range of benign and malignant histiocytic disorders and found that ZBTB46 is able to clearly define the dendritic cell identity of many previously unclassified histiocytic disease subtypes. In particular, all examined cases of Langerhans cell histiocytosis and histiocytic sarcoma expressed ZBTB46, while all cases of blastic plasmacytoid dendritic cell neoplasm, chronic myelomonocytic leukemia, juvenile xanthogranuloma, Rosai-Dorfman disease, and Erdheim-Chester disease failed to demonstrate expression of ZBTB46. Moreover, ZBTB46 expression clarified the identity of diagnostically challenging neoplasms, such as cases of indeterminate cell histiocytosis, classifying a fraction of these entities as dendritic cell malignancies. These findings clarify the lineage origins of human histiocytic disorders and distinguish dendritic cell disorders from all other myeloid neoplasms.

Histiocytic cell neoplasms involving the bone marrow: summary of the workshop cases submitted to the 18th Meeting of the European Association for Haematopathology (EAHP) organized by the European Bone Marrow Working Group, Basel 2016

The bone marrow is a preferential site for both reactive and neoplastic histiocytic proliferations. The differential diagnosis ranges from reactive histiocyte hyperplasia in systemic infections, vaccinations, storage diseases, post myeloablative therapy, due to increased cell turnover, and in hemophagocytic lymphohistiocytosis, through extranodal Rosai-Dorfman disease to neoplasms derived from histiocytes, including histiocytic sarcomas (HS), Langerhans cell histiocytoses (LCH), Erdheim-Chester disease (ECD), and disseminated juvenile xanthogranuloma (JXG). One of the most important recent developments in understanding the biology of histiocytic neoplasms and in contributing to diagnosis was the detection of recurrent mutations of genes of the Ras/Raf/MEK/ERK signaling pathway, in particular the BRAF^V600E mutation, in LCH and ECD. Here, we summarize clinical and pathological findings of 17 histiocytic neoplasms that were presented during the bone marrow symposium and workshop of the 18th European Association for Haematopathology (EAHP) meeting held in Basel, Switzerland, in 2016. A substantial proportion of these histiocytic neoplasms was combined with clonally related lymphoid (n = 2) or myeloid diseases (n = 5, all ECD). Based on the latter observation, we suggest excluding co-existent myeloid neoplasms at initial staging of elderly ECD patients. The recurrent nature of Ras/Raf/MEK/ERK signaling pathway mutations in histiocytic neoplasms was confirmed in 6 of the 17 workshop cases, illustrating their diagnostic significance and suggesting apotential target for tailored treatments.