Langerhans Cell Histiocytosis Cells Research Articles

Cyclin D1 Is Expressed in Neoplastic Cells of Langerhans Cell Histiocytosis but Not Reactive Langerhans Cell Proliferations.

Langerhans cell histiocytosis (LCH) is characterized by frequent activating mutations involving the mitogen-activated protein kinase (MAPK) pathway. Therefore, downstream markers of MAPK pathway activation such as cyclin D1 may be useful as novel diagnostic markers of neoplasia in LCH. The goal of this study was to investigate cyclin D1 expression in LCH and reactive Langerhans cell accumulations using immunohistochemistry on archival tissue. All LCH cases tested (39/39) showed cyclin D1 expression in CD1a/Langerin cells. Most cases (22/39; 56%) showed strong cyclin D1 expression in the majority (≥50%) of lesional cells. Only a few cases (6/39; 15%) showed cyclin D1 expression in a small subset (<20%). Nearly all LCH cases (26/27; 96%) showed p-ERK expression by immunohistochemistry, parallel to cyclin D1 expression. CD1a Langerhans cells in all cases of florid dermatopathic lymphadenopathy and normal skin were negative for cyclin D1, as demonstrated by CD1a/cyclin D1 double staining. The majority of skin specimens (14/18; 78%) with dermatitis-related changes did not show cyclin D1 expression in the CD1a epidermal Langerhans cell aggregates. A minority (4/18; 22%) showed weak cyclin D1 staining in a small subset (5% to 10%) of CD1a Langerhans cells. We conclude that cyclin D1 is ubiquitously expressed in LCH, in keeping with the known near universal MAPK activation in this disease. Further, it is not significantly expressed in reactive Langerhans cell proliferations in lymph node or skin. Therefore, cyclin D1 immunohistochemistry may be useful in excluding non-neoplastic mimics of LCH.

Killer cell immunoglobulin-like receptor 2DL4 is expressed in and suppresses the cell growth of Langerhans cell histiocytosis.

Killer cell immunoglobulin-like receptor (KIR) 2DL4 (CD158d) is a receptor for human leukocyte antigen-G. The function of KIR2DL4 has been reported in human natural killer cell lymphoma and mastocytosis, but not in Langerhans cell histiocytosis (LCH). Herein, we examined the expression and function of KIR2DL4 in LCHs. In pathological specimens, 27 of 36 LCH cases (75.0%) were immunohistochemically positive for KIR2DL4. Its expression was independent of age, gender, location, multi- or single-system, and the status of BRAFV600E immunostaining. We also confirmed the expression of KIR2DL4 mRNA and protein in the human LCH-like cell lines ELD-1 and PRU-1. KIR2DL4 protein was distributed in the membrane and cytoplasm of ELD-1 cells, but only in the cytoplasm of PRU-1 cells. An agonistic antibody against KIR2DL4 reduced phosphorylation of extracellular signal-regulated kinases (ERKs) and suppressed the cell growth of ELD-1 cells in a Src homology region 2 domain-containing phosphatase-2 dependent manner, but it had no effect in PRU-1 cells. These results suggest that KIR2DL4-mediated ERK suppression is a possible therapeutic target for LCH cells.

Clonal, Exhausted and Activated Infiltrating T Lymphocytes in Langerhans Cell Histiocytosis Lesions

Background: Langerhans Cell Histiocytosis (LCH) is characterized by inflammatory lesions with pathologic CD207+ dendritic cells (DCs) with constitutively activated ERK. LCH lesions are associated with a local cytokine storm and exhibit a heterogeneous collection of inflammatory infiltrates (eosinophils, neutrophils and lymphocytes). The mechanisms behind tumor formation, both accumulation of pathologic CD207+ DCs as well as recruitment of inflammatory infiltrate, remain to be defined. Mutually exclusive somatic mutations in MAPK pathway genes have been identified in approximately 75% of LCH cases, including recurrent BRAF-V600Eand MAP2K1 mutations. However, the inflammatory infiltrate within LCH lesions is composed of cells without any BRAF mutation or ERK activation. We hypothesize that the pathologic inflammation in LCH is orchestrated by interactions between the pathologic MAPK-activated DCs and normal immune cells. Defining the nature and function of infiltrating T cells in LCH will not only provide insights into mechanisms of pathogenesis and potential therapeutic targets, but may also inform novel physiologic mechanisms of DC-mediated T cell function.Methods: Clonality was investigated by exploring T cell receptor beta (TCRB) rearrangement in LCH patients. Quantitative analysis of different immune cell populations in the tumor microenvironment in 25 LCH patients was performed using spanning tree progression of density normalized events (SPADE).Results: Our initial experiments identified clonal populations among LCH lesion-infiltrating CD3+ T cells. The complementarity-determining region 3 (CDR3) of the TCRBV07 gene demonstrated marked monoclonal expansion, suggesting a potential involvement of antigen selection in the pathogenesis of LCH. SPADE analysis of infiltrating CD3+ T cells revealed high expression of T cell immunoglobulin mucin (TIM-3), lymphocyte activated gene 3 (LAG3) and programmed cell death protein 1 (PD-1) compared to healthy controls, indicating that effector T cell exhaustion might be an important mechanism of immune dysregulation in LCH patients. In addition, in a cohort of LCH patients harboring wild-type BRAF, but not the BRAF-V600E mutation, a distinct subset of infiltrating CD3+ T cells were detected expressing both CD4 and CD8α receptors at high levels (double-positive, DP). Preliminary analysis showed high levels of IFNγ, but not TNF-α, after stimulation of these DP T cells.Conclusions: The results from this study support a model in which LCH lesion DCs with activated MAPK signaling select and recruit activated T cells with potential for clonal expansion to LCH lesions. Multiple markers of T cell exhaustion were identified on infiltrating LCH lesion T cells. While the significance of double-positive T cells in LCH is uncertain, similar cells have been reported in the target organs of several auto-immune conditions and hematological and solid malignancies, consistent with double-positive T cells in sites of immune exhaustion. The function of this double-positive T cell population remains to be defined, but we postulate that these cells may participate in tumor immune responses in LCH due to their potential of having broad tumor reactivity. While the CD207+ DCs in LCH lesions is histologically uniform across the disease spectrum, the composition of the immune microenvironment is variable. The variability of the DP T cell population in BRAF-V600E vs BRAF wild-type DCs study suggests that specific mechanisms of MAPK activation may have some distinct impact on T cell recruitment and activation. While recent discoveries have enhanced understanding of the origin and aberrant MAPK activation of the pathologic DCs, very little is known about the role of lymphocytes or the inflammatory microenvironment. Characterizing the populations, function, and interactions of the LCH lesion immune cells may provide novel therapeutic opportunities, such as checkpoint inhibitors. Further, identifying the mechanisms that underlie the "cytokine storm" of LCH lesion may inform physiologic interactions between MAPK-activated DCs and effector immune cells. DisclosuresNo relevant conflicts of interest to declare.

Neurohistiocytose langerhansienne

Langerhans cell histiocytosis (LCH) is a rare multisystemic disease. LCH is characterized by proliferation of myeloid progenitors with altered differentiation program and similar phenotypic features to epidermal dendritic cells termed Langerhans cell. LCH cells express CD1a+ and langerin and exhibit BRAF V600E mutation in ∼50% of cases. Neurological involvement or neuro-LCH is observed in 5 to 10% of cases. Three subtypes of neuro-LCH are individualized. The tumor type, accounting for 45% of neuro-LCH, affect mainly young adults. Tumor neuro-LCH is characterized by space occupying lesion(s) with contrast enhancement on MRI. Clinical symptoms are due to tumor brain location(s). Pathological examination of tumor neuro-LCH lesions reveals typical features of LCH. Treatment relies on surgical resection with/without chemotherapy. Degenerative neuro-LCH, accounting for 45% of cases, is usually revealed, mostly in children, by: (i) a cerebellar syndrome, (ii) a pyramidal syndrome, (iii) a pseubulbar palsy, and/or (iv) cognitive disorders. On MRI, several signs may coexist: (i) cortex atrophy, (ii) white matter T2 hyperintensities, and (iii) deep gray matter T1 hyperintensities. Pathological analysis of degenerative neuro-LCH lesions have been rarely performed and have never detected CD1a+ histiocytes but unspecific lesions (i.e. gliosis, neuronal loss and/or demyelination). Treatment of degenerative neuro-LCH patients is poorly standardized and poorly efficient. Functional rehabilitation and socio-educational care of these young patients are crucial. The mixed subtype of neuro-LCH combines clinico-radio-pathological characteristics of the first two first forms in the same patient, and represents 10% of neuro-HL. Neuro-HL, therefore, includes three very distinct entities with epidemiological, clinical, radiological and histological specific features requiring specific medical management.

BRAFV600E and MAP2K1 mutations in Langerhans cell histiocytosis occur predominantly in children.

Langerhans cell histiocytosis (LCH) is a proliferative disease of CD1a+ /CD207+ dendritic cells. Recurrent BRAFV600E and MAP2K1 mutations have been reported in LCH. To investigate the relationship among the mutation, clinical findings, and differentiation status of LCH, respectively, we studied 97 cases of LCH by using Sanger sequencing and immunohistochemistry. The mutually exclusive BRAFV600E and MAP2K1 mutation rates were 32% and 17.5%, respectively. All MAP2K1 mutations were missense mutations without any in-frame deletions; 2 new recurrent missense mutations (ie, p.E38K and p.P105S) were also found. More BRAFV600E and MAP2K1 mutations occurred in children compared with those in adult patients (P=.001), and BRAF mutation was correlated with relapse (P=.009). To the differentiation-related markers, the BRAF/MAP2K1-mut LCH expressed CD14 but rarely expressed CD83 or CD86 (P<.001). On the contrary, BRAF/MAP2K1-wt LCH cells rarely expressed CD14 but expressed CD86, and some also expressed CD83 (P<.001). This indicated that the BRAF/MAP2K1-mut LCH cells had a more immature state than BRAF/MAP2K1-wt LCH cells. Moreover, we also found the BRAFV600E and MAP2K1 mutations were significantly associated with pERK expression (P<.001). Therefore, the RAS/RAF/MEK/ERK pathway might play a more important role in children than in adult patients with LCH.

Langerhans cell histiocytosis is a neoplasm and consequently its recurrence is a relapse: In memory of Bob Arceci.

Langerhans cell histiocytosis (LCH) remains a poorly understood disorder with heterogeneous clinical presentations characterized by focal or disseminated lesions that contain excessive CD1a+ langerin+ cells with dendritic cell features known as "LCH cells." Two of the major questions investigated over the past century have been (i) the origin of LCH cells and (ii) whether LCH is primarily an immune dysregulatory disorder or a neoplasm. Current opinion is that LCH cells are likely to arise from hematopoietic precursor cells, although the stage of derailment and site of transformation remain unclear and may vary in patients with different extent of disease. Over the years, evidence has provided the view that LCH is a neoplasm. The demonstration of clonality of LCH cells, insufficient evidence alone for neoplasia, is now bolstered by finding driver somatic mutations in BRAF in up to 55% of patients with LCH, and activation of the RAS-RAF-MEK-ERK (where MEK and ERK are mitogen-activated protein kinase and extracellular signal-regulated kinase, respectively) pathway in nearly 100% of patients with LCH. Herein, we review the evidence that recurrent genetic abnormalities characterized by activating oncogenic mutations should satisfy prerequisites for LCH to be called a neoplasm. As a consequence, recurrent episodes of LCH should be considered relapsed disease rather than disease reactivation. Mapping the complete genetic landscape of this intriguing disease will provide additional support for the conclusion that LCH is a neoplasm and is likely to provide more potential opportunities for molecularly targeted therapies.

Acute-phase ITIH4 levels distinguish multi-system from single-system Langerhans cell histiocytosis via plasma peptidomics.

BackgroundLangerhans cell histiocytosis (LCH) is a proliferative disorder in which abnormal Langerhans cell (LC)-like cells (LCH cells) intermingle with inflammatory cells. Whether LCH is reactive or neoplastic remains a controversial matter. We recently described Merkel cell polyomavirus (MCPyV) as a possible causative agent of LCH and proposed interleukin-1 loop model: LCH is a reactive disorder with an underlying oncogenic potential and we now propose to test this theory by looking for acute markers of inflammation. We detected MCPyV-DNA in the peripheral blood cells of patients with high-risk organ-type (LCH-risk organ (RO) (+)) but not those with non–high-risk organ-type LCH (LCH-RO (−)); this difference was significant. LCH-RO (−) is further classified by its involvement of either a single organ system (SS-LCH) or multiple organ systems (MS-LCH). In patients with LCH-RO (−), MCPyV-DNA sequences were present in LCH tissues, and significant differences were observed between LCH tissues and control tissues associated with conditions such as dermatopathic lymphadenopathy and reactive lymphoid hyperplasia. Although MCPyV causes subclinical infection in nearly all people and 22 % of healthy adults will harbor MCPyV in their buffy coats, circulating monocytes could serve as MCPyV reservoirs and cause disseminated skin lesions.MethodsPlasma sample from 12 patients with LCH-RO (−) (5 MS-LCH and 7 SS-LCH) and 5 non-LCH patients were analyzed by peptidomics. Mass spectrometry (MS) spectra were acquired and peptides exhibiting quantitative differences between MS-LCH and SS-LCH patients were targeted.ResultsOne new candidate biomarker, m/z 3145 was selected and identified after obtaining a MS/MS fragmentation pattern using liquid chromatography-MS/MS. This peak was identified as a proteolytic fragment derived from inter-alpha-trypsin inhibitor heavy chain 4 (ITIH4, [PDB: Q14624]).ConclusionsPeptidomics of LCH have revealed that the level of acute-phase ITIH4 distinguishes MS-LCH-RO (−) from SS-LCH-RO (−). Acute-phase proteins serve non-specific, physiological immune functions within the innate immune system. LCH may be a reactive disorder with both underlying neoplastic potential of antigen presenting cells harboring BRAF mutations and hyper-immunity of other inflammatory cells against MCPyV infection. Among LCH-RO (−), MCPyV-DNA sequences were present in both MS-LCH tissues and SS-LCH tissues without significant differences. ITIH4 may show that LCH activity or LCH subtypes correlates with the systemic or localized reactions of MCPyV infection.

MAP2K1 and MAP3K1 mutations in Langerhans cell histiocytosis.

Langerhans cell histiocytosis (LCH) is now understood to be a neoplastic disease in which over 50% of cases have somatic activating mutations of BRAF. However, the extracellular signal-related (ERK) pathway is activated in all cases including those with wild type BRAF alleles. Here, we applied a targeted massively parallel sequencing panel to 30 LCH samples to test for the presence of additional genetic alterations that might cause ERK pathway activation. In 20 BRAF wild type samples, we found 3 somatic mutations in MAP2K1 (MEK1) including C121S and C121S/G128D in the kinase domain, and 56_61QKQKVG>R, an in-frame deletion in the N-terminal regulatory domain. All three variant proteins constitutively phosphorylated ERK in in vitro kinase assays. The C121S/G128D and 56_61QKQKVG>R variants were resistant to the mitogen-activated protein kinase kinase (MEK) inhibitor trametinib in vitro. Within the entire sample set, we found 3 specimens with mutations in MAP3K1 (MEKK1), including two truncation mutants, T779fs and T1481fs; T1481fs encoded an unstable and nonfunctional protein when expressed in vitro. T779fs was present in a specimen carrying BRAF V600E. The third variant was a single nucleotide substitution, E1286V, which was fully functional and is likely a germline polymorphism. These results indicate that LCH cells can harbor additional genetic alterations in the RAS-RAF-MEK pathway which, in the case of MAP2K1, may be responsible for ERK activation in a wild type BRAF setting. The resistance of some of these variants to trametinib may also have clinical implications for the combined use of RAF and MEK inhibitors in LCH.

Interleukin-1 loop model for pathogenesis of Langerhans cell histiocytosis.

We propose Langerhans cell histiocytosis (LCH) is an inflammatory process that is prolonged by mutations. We hypothesize that Merkel cell polyomavirus (MCPyV) infection triggers an interleukin-1 (IL-1) activation loop that underlies the pathogenesis of LCH. Langerhans cells (LCs) are antigen presenting cells in the skin. When LCs encounter exogenous antigens, they migrate from the epidermis into draining lymphoid tissues to initiate T-cell activity. It has been proposed that LC migration-related factors, including E-cadherin, matrix metalloproteinase, and Notch ligand induce LCH activity. We found that the tyrosine phosphatase SHP-1, which binds IL-1 receptor-associated kinase 1, is expressed at a significantly higher level in LCH affecting multiple organ systems (MS-LCH) than in LCH affecting a single organ system (SS-LCH). IL-1 stimulates T helper 17 cells and their signature cytokine IL-17 had been a matter of controversy. We detected higher levels of IL-17A receptor expression in MS-LCH than in SS-LCH and proposed an IL-17 endocrine model that could settle the controversy. IL-1 is the first cytokine secreted in response to sensitizers and promotes LC migration from sentinel tissues. Myeloid differentiation primary response 88 (MyD88), downstream of the IL-1 receptor, has functions in both RAS signaling and inflammation, leading to human cell transformation. In 2010, an activating mutation in the B-rapidly accelerated fibrosarcoma gene (BRAF) V600E was found in LCH. This BRAF mutation induces phosphorylation of the extracellular signal-regulated kinase (ERK) that may play an important role with MyD88 in LCH pathogenesis. However, phosphorylated ERK (pERK) is rapidly dephosphorylated by dual specificity phosphatase 6 (DUSP6), and limited proliferation is predicted in BRAF mutant cells. MyD88 binds pERK via its D-domain, thereby preventing pERK–DUSP6 interaction and maintaining ERK in an active, phosphorylated state. We detected MCPyV-DNA in the peripheral blood cells of two out of three patients with LCH in high-risk organs but not in those of patients with LCH in non–high-risk organs (0/12; P = .029). MCPyV infection can trigger precursor LCH cells with BRAF mutation to produce IL-1; the IL-1 loop is amplified in all LCH subclasses. Our model indicates both BRAF mutation and IL-1 loop regulation as potential therapeutic targets.

Highly Elevated IL-18 Is a Reliable Predictor of Progression to Hemophagocytic Syndrome in the Patients with Langerhans Cell Histiocytosis

▪Introduction:Langerhans cell histiocytosis (LCH) is a rare proliferative disorder of epidermal antigen-presenting cells such as dendritic cells (DCs). Historically, three distinct clinical syndromes have been described: eosinophilic granuloma (EG), Hand-Schuller-Christian disease and Letterer-Siwe disease (LSD). The disease has a broad spectrum of clinical behavior, from a mild self-limited form like EG-type LCH to an aggressive form associated with a high mortality rate like LSD-type LCH. Since one of the lethal complications of LCH is hemophagocytic syndrome (HPS), investigating a novel treatment approach for LCH associated HPS (LCH-HPS) is of paramount importance.We have reported the usefulness of cytokine profiles to differentiate HPS from various inflammatory diseases, in which macrophages/monocytes derived cytokines such as interleukin (IL)-18 and neopterin were highly elevated. Since clinical trials using neutralizing antibody to IL-18 in rheumatoid arthritis or plaque psoriasis are now underway, in this study, we examined cytokine profiles over time from six LCH cases and investigated the significance of IL-18 in the pathophysiology of HPS to establish a unique treatment strategy for LCH-HPS.Materials and Methods:The concentrations of serum IL-18 were measured in six patients with LCH, including three patients with EG-type LCH and three with LSD-type LCH. Diagnosis of LCH and HPS were based on clinical and histopathological findings. Serum IL-18 levels were measured by enzyme-linked immunosorbent assay (ELISA). Total RNA was extracted from tumor samples for analysis of IL-18 and LANGERIN mRNA expression. BRAF gene mutation was analyzed using DNA extracted from tumor cells as previously described.Results:Serum IL-18 level of LSD-type LCH was significantly higher than that of EG-type LCH (median 13,600 vs. 449, p<0.05) (Figure 1). In fact, two out of three LSD-type LCH cases developed LCH-HPS, whereas none of the cases with low level of IL-18 developed. When developed to HPS caused by various disorders, serum IL-18 concentrations became markedly increased as shown in Figure 1, suggesting that IL-18 plays a pivotal role in macrophage activation to develop HPS even in LCH. Serum concentration of IL-18 recovered to and maintained normal range after induction chemotherapy. We also observed a dominant increase of soluble tumor necrosis factor alpha-receptor type I (sTNF-RI) and type II (sTNF-RII) in LSD-LCH cases in addition to essential parameters for HPS: IL-18 and neopterin (Figure 2). This unique cytokine profile of LCH-HPS might be the cause of higher mortality rate (20%) compared to HPS caused by various disorders (5-10%).BRAF V600E mutation was detected in one of the three cases in each EG-type LCH and LSD-type LCH, suggesting that existence of BRAF V600E mutation does not correlate to the disease severity as previously reported.As recent studies demonstrated that LCH was originated from DCs, which were close to macrophages/monocytes systems, we hypothesized that LSD-type LCH tumor cells secret IL-18, and then directly initiate macrophage activation to develop HPS. To test this, we assessed IL-18 mRNA expression in tumor cells from LSD-type LCH by RT-PCR. LANGERIN mRNA expression was enhanced from all the LSD-type LCH tumor cells, however IL-18 mRNA did not seem to be derived from tumor cells, suggesting that LSD-type LCH cells themselves would trigger lethal HPS similar to lymphoma associated HPS.Conclusion:In conclusion, though LSD-type LCH tumor cells did not express IL-18 directly, the level of IL-18 was much higher in LSD-type LCH. Paying carful attention should be required to the patients with LSD-type LCH with highly elevated IL-18 to prevent the progression of lethal LCH-HPS. To hamper the macrophage activation, an application of IL-18 antibody may be clinically useful for the disease control of LCH-HPS. [Display omitted] [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Establishment of a Langerhans cell histiocytosis lesion cell line with dermal dendritic cell characteristics.

A cell line named PRU-1, derived from a Langerhans cell (LC) histiocytosis (LCH) skull lesion of a 7-year-old boy, was established and characterized. PRU-1 is an adherent spindle-shaped cell line that shows no Birbeck granules on electron microscopy. Flow cytometric analysis of cells collected from the early seventh passage showed no LC phenotypes of CD1a and S100 protein. Immunostaining of PRU-1 cells also revealed no expression of LC markers but showed expression of CD11c, CD54 (ICAM-1) and CD68, which was also observed in some peripherally located cells of the original LCH lesion. The PRU-1 cells stained positive for factor XIIIa and negative for CD34, suggesting a dermal dendritic cell phenotype. Cytogenetic analyses revealed abnormalities such as 39,XY,-2,-4,-8,-12,-12,-14,add(18)(q21),20,+mar and 44,XY,-11,-14,add(18)(q21). TCRγ rearrangement in the PRU-1 cells was not amplified by PCR. Tumorigenicity was not proven by xenografting into SCID mice. A conditioned medium from PRU-1 culture induced the proliferation of peripheral blood lymphocytes as well as the activation of monocytes from a healthy donor into CD1a-positive LC-like cells. Because the phenotypic characteristics of PRU-1 differed from those of CD1a-positive abnormal LC-like cells (LCH cells), it was likely that the PRU-1 cells were derived from peripherally located cells of the LCH lesion rather than LCH cells. LCH has been regarded as a type of granulomatous neoplasm with several intermingled inflammatory cells and influenced by stimuli such as Merkel cell polyomavirus (MCPyV) infection or cigarette smoking. However, in the PRU-1 cells, MCPyV-DNA was not detected by PCR. Stromal cell-like PRU-1 cells are likely to produce some growth or differentiation factors, which may play important roles in LCH lesion formation, cell maintenance and LC-like cell induction.

English

Langerhans cell histiocytosis (LCH) is a rare proliferative disorder in which pathological Langerhans cells (LCs) accumulate in a variety of organs. This report describes a boy with Langerhans' cell histiocytosis who presented with primarily soft tissue swellings, without pain. A high index of suspicion is required to reach to a diagnosis of langerhans cell histiocytosis to prevent delay in proper management of this disease. INTRODUCTION: The childhood histiocytoses, although individually rare, varies widely in its clinical expression. These disorders are grouped together because they have in common a prominent proliferation or accumulation of cells of the monocyte-macrophage system of bone marrow origin. (1) A systematic classification of the childhood histiocytoses is based on histopathologic findings. The name Langerhans cell histiocytosis (LCH) has been applied to the class I histiocytoses. The normal Langerhans cell is an antigen-presenting cell of the skin. The hallmark of LCH in all forms is the presence of a clonal proliferation of cells of the monocyte lineage containing the characteristic electron microscopic findings of a Langerhans cell. This is the Birbeck granule, a tennis racket-shaped bilamellar granule that, when seen in the cytoplasm of lesional cells in LCH, is diagnostic of the disease. (1) CASE REPORT: A 4 year old male child presented to our pediatric outpatient department of mamata medical college with the chief complaint of multiple swellings over the forehead for the last one year. The child was apparently normal one year back when his parents noticed multiple small swellings which were gradually progressing in size. The child is a product of non-consanguineous marriage, full term, normal vaginal delivery and has a younger sister who is doing well. On examination there were three swellings over the forehead, which were subcutaneous, nontender margins ill-defined and with underlying bony defects in center of the swellings. Bilateral exophthalmos was present There was no organomegaly, generalized lymphadenopathy, skin manifestations or ear discharge.

Somatic activating ARAF mutations in Langerhans cell histiocytosis

AbstractThe extracellular signal-regulated kinase (ERK) signaling pathway is activated in Langerhans cell histiocytosis (LCH) histiocytes, but only 60% of cases carry somatic activating mutations of BRAF. To identify other genetic causes of ERK pathway activation, we performed whole exome sequencing on purified LCH cells in 3 cases. One patient with wild-type BRAF alleles in his histiocytes had compound mutations in the kinase domain of ARAF. Unlike wild-type ARAF, this mutant was a highly active mitogen-activated protein kinase kinase in vitro and was capable of transforming mouse embryo fibroblasts. Mutant ARAF activity was inhibited by vemurafenib, a BRAF inhibitor, indicating the importance of fully evaluating ERK pathway abnormalities in selecting LCH patients for targeted inhibitor therapy.

Comparison of magnetic resonance imaging with invasive histological findings of Langerhans cell histiocytosis

Due to the rarity of skull Langerhans cell histiocytosis (LCH), correlations between abnormalities on magnetic resonance imaging (MRI) and pathological findings have not been fully evaluated. Only a few reports have as yet compared MRI of LCH infiltration and histological diagnostic features. A 22-year-old man with an unremarkable past medical history presented with headache followed by a nodular mass in the right parietal area. Gadolinium (Gd)-enhanced T1-weighted images showed a "mushroom-shaped" extension, extending from the subcutaneous to the intracranial space. The galeal tissue, the dura mater, and the cranium adjacent to the lesion showed enhancement on Gd-enhanced T1-weighted MRI. Histologically, diagnosis was LCH, with immunohistochemical positivity for S-100, CD68, and CD1a, and showed a MIB-1 labeling index of 29.5%. By immunostaining, we confirmed LCH cells to be present in the galea with Gd enhancement and the skull without Gd enhancement on MRI. LCH cells might exist in the marginal cranium, if MRI shows only slight intensity change without Gd enhancement. Further evaluation to determine pathologically proven extent of LCH and its relation with neuroradiological diagnosis as well as clinical outcome is needed to understand heterogeneous response to surgical and/or nonsurgical treatment in LCH.

Evaluation of Patients with Intracranial Tumors and Central Diabetes Insipidus

The aim of the study is to evaluate the etiologic and clinical characteristics, treatment regimens, and outcome of the patients with intracranial tumors presenting with central diabetes insipidus (DI). Sixty-nine patients with intracranial tumors presenting with central DI between 1972 and 2012 were retrospectively evaluated. Fifty-three out of 69 patients were included in the analysis. Male/female ratio was 1.52, median age was 7.6 years. Of 53 patients, 37 patients (69.8%) were diagnosed with Langerhans cell histiocytosis, 14 patients (26.4%) with germinoma, 1 (1.9%) with astrocytoma, and 1 (1.9%) with optic glioma. 10-year overall survival (OS) rate and disease-free survival rate for all patients were 91.7% and 52%. 10-year OS rate according to diagnostic criteria was 91% for Langerhans cell histiocytosis (LCH) cases, 79% for intracranial germinoma, which was statistically significant (P = .0001). Central DI may be very important clinical presentation of serious underlying disease in children. Intracranial tumors are the most frequent cause of DI. Most frequent diagnosis were LCH and germ cell tumors in our series.

Hypothetical pathogenesis of eosinophilic infiltration in Langerhans cell histiocytosis of the jaw

The present study investigated the densities of mast cells and CCL-11/eotaxin-1 expression of tumor cells in Langerhans cell histiocytosis (LCH) of the jaw. Eleven LCH cases arising in the jaws were selected. We evaluated eotaxin-1 expression in LCH cells via immunohistochemical staining. Toluidine blue was used to stain mast cells, with 20 periapical granuloma specimens serving as the control group. In all 7 patients with multifocal LCH, jaw lesions were the earliest manifestation. Toluidine blue staining revealed that most of the mast cells involved in LCH were degranulated, and the number of mast cells in LCH lesions was not significantly higher than in periapical granulomas. Upon immunohistochemical examination, all patients but one showed positivity for eotaxin-1 in LCH cells. This preliminary study suggests that eotaxin-1 expression in LCH cells may contribute to eosinophilic infiltration. Further studies of chemokine-receptor interactions will be needed to confirm this.

The Origin and Function of Langerin (CD207) Expressing Cells in Mice and Humans

Abstract SCI-7The current paradigm suggests that Langerhans cell histiocytosis (LCH) results from an accumulation of epidermal dendritic cells also called Langerhans cells. This concept is based on phenotypic and ultrastructural observations showing that LCH lesions are infiltrated by CD1a+langerin+ cells, two features thought to be restricted to epidermal Langerhans cells. It has been difficult, however, to understand how Langerhans cells, which are normally restricted to stratified epithelia, could give rise to such a multifocal disorder. LCH research has been handicapped by the inability to develop reliable animal models and by the fact that for a long time very few markers were available to determine the origin and stage of differentiation of histiocytes, now renamed macrophage/dendritic cell lineages. This presentation will discuss recent progress in our understanding of the regulation of the Langerhans cell, macrophage, and dendritic cell lineages and discuss the relationship of these lineages with the LCH cell. Disclosures:No relevant conflicts of interest to declare.

Identification of the V600D mutation in Exon 15 of the BRAF oncogene in congenital, benign langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is a well-known but rare disease that may occur at any age with markedly variable clinical features: self-regressive, localized, multiorgan, aggressive, or fatal outcome. Congenital LCH is rare and often clinically benign. While LCH is characterized by a clonal proliferation of Langerhans cells, its etiology is unknown. Although BRAF V600E mutations were recently identified as a recurrent genetic alteration in LCH cases, the clinical significance of this mutation within the heterogeneous spectrum of LCH is also currently unknown. We studied a cutaneous, benign form of congenital LCH that occurred in a newborn male, without recurrence for 8 years. Histopathologically, the skin lesion excised after birth showed the typical cytologic and immunophenotypic features of LCH. Sequencing analysis of Exon 15 of the BRAF gene revealed the V600D mutation, with an allelic abundance of 25-30%, corresponding to the LCH cells being hemizygous for the mutant allele. BRAF V600E-specific polymerase chain reaction was negative. Our report is the first to identify the rare, variant BRAF V600D mutation in LCH, and provides support for constitutively activated BRAF oncogene-induced cell senescence as a mechanism of regression in congenital, benign LCH. Further, our clinicopathologic findings provide proof for the first time that the V600D mutation can also occur in the absence of ultraviolet light, and can occur in a clinically benign proliferation, similar to the V600E mutation. Additional clinicopathologic studies in larger numbers of LCH patients may be valuable to ascertain the pathophysiologic role of BRAF mutations in LCH.

Paraneoplastic disseminated lentigines heralding aggressive Langerhans cell sarcoma

Dear Editor, A 21-year-old man presented with a rapidly growing (9 cm), non-tender right flank mass with superficial excoriation and inflammation (Fig. 1a). The lesion was accompanied by rapid onset of disseminated brown papules, involving the torso, back, and limbs (Fig. 1b). Facial and axillary skins were spared, and there was no particular direction of spread. The skin patches did not coalesce or show pruritus or inflammation. There was also weight loss of 15 lb in 3 months. A positron emission tomogram scan (PET) showed FDG uptake in the right waist (SUV 5.8) and right groin (SUV 2.1) (Fig. 1c). Wide margin resection of the mass and lymph node excision was performed with clear margins. Histology of both specimens showed sheets and loose clusters of pleomorphic malignant cells infiltrating the dermis and subcutis with frequent mitosis (Fig. 1d). In view of the anaplastic morphology and unusual presentation, extensive immunophenotyping was performed. The cells were positive for CD1a, S100, and Langerin stains. They were negative for melanocytic markers (HMB45, melan-A, MITF) EMA, cytokeratin (CK, Cam 5.2, 34betaE12), actin, desmin, CD31, CD34, c-kit, B and T markers (CD20, CD79a, CD3), CD68, CD30, CD56, CD21, MPO, and ALK1. Electron microscopy for Birbeck granules was not performed. The picture was compatible with Langerhans cell sarcoma (LCS). A separate skin biopsy of a pigmented lesion on the torso showed elongated rete ridges with increased basal melanin pigmentation within keratinocytes and the tips, with no increased Langerhans cells and no evidence of malignancy or dysplasia. The lesion was compatible with common lentigo. The patient was treated with consolidation radiotherapy to the primary sites, but there was no regression of the skin lentiges. Fig. 1 a Clinical photo showing the flank mass with impending ulceration. b Widespread lentiginous lesion all over the trunk heralding the rapid growth of the malignant lesion. c PET with maximum intensity projection showing two sites of active lesions in the ... In the World Health Organization classification, LCS is the malignant end of the spectrum of benign Langerhans cell histiocytosis (LCH) [1]. The typical LCH cell is replaced by pleomorphic tumor cells in the LCS, only identifiable by phenotype or ultrastructure. Initial unifocal subcutaneous involvement is not unusual. However progressive disease, especially with multifocal dissemination, is highly fatal, despite multi-agent chemotherapy. It remains to be seen whether systemic progression may occur in our patient. Our patient demonstrated two hitherto unreported phenomena, namely paraneoplastic manifestation of LCS and acquired rampant disseminated lentigines as a new paraneoplastic dermatosis. The clinical history and histological findings do not suggest an underlying disseminated cutaneous LCH. Common paraneoplastic dermatoses (e.g., acanthocis nigricans) are well characterized and are putatively caused by neoplastic humoral secretions. Acquired melanocytic nevi are mostly related to solar exposure and are therefore localized. Recently, some cases of acral lentigines are debated to be paraneoplastic [2]. Disseminated lentigines are usually only found in familial lentiginosis syndromes (e.g., LEOPARD syndrome, Peutz–Jeghers, Carney complex, PTEN hamartoma syndrome). The neoplastic associations of these syndromes come from their primary systemic gene mutations [3]. The rapidly acquired disseminated growth of lentigines in our case is highly unusual and is somewhat induced by the abnormal aggressive transformation of the LCS cells. Skin pigmentation is usually under exquisite humoral control [4], and cutaneous Langerhans cells interact closely with melanocytes and keratinocytes [5]. It is impossible, however, to retrospectively work out the exact mechanism how the localized growth induced a systemic pigment response, since interval archival specimens are unavailable and the list of possible mediators are extensive. In any case, extirpation of the primary lesion appeared to halt further skin lesions.

Pathogenesis of Langerhans Cell Histiocytosis

Langerhans cell histiocytosis (LCH) combines in one nosological category a group of diseases that have widely disparate clinical manifestations but are all characterized by accumulation of proliferating cells with surface markers and ultrastructural features similar to cutaneous Langerhans cells (LCs). Despite this unified nosology, important questions about LCH remain unanswered. First, despite having phenotypic features of LCs, LCH cell gene-expression patterns differ from those in LCs. Although this observation suggests that LCH may arise from an earlier precursor, it is not necessarily inconsistent with the hypothesis that LCs are the cell of origin for LCH. Second, LCH's prominent inflammatory component and occasional benign clinical course suggest that LCH may not be a neoplasm. However, the demonstration that LCH cells are clonal, along with the recent discovery of activating BRAF mutations in LCH cells, strongly suggests that LCH is a neoplastic disease. These new observations point the way to rationally targeted therapies.