Cytogenetic abnormalities in Langerhans cell histiocytosis

Identification and characterization of stromal-like cells with CD207+/low CD1a+/low phenotype derived from histiocytic lesions - a perspective in vitro model for drug testing

BACKGROUND

Histiocytoses are rare disorders manifested by increased proliferation of pathogenic myeloid cells sharing histological features with macrophages or dendritic cells and accumulating in various organs, i.a., bone and skin. Pre-clinical in vitro models that could be used to determine molecular pathways of the disease are limited, hence research on histiocytoses is challenging. The current study compares cytophysiological features of progenitor, stromal-like cells derived from histiocytic lesions (sl-pHCs) of three pediatric patients with different histiocytoses types and outcomes. The characterized cells may find potential applications in drug testing.

METHODS

Molecular phenotype of the cells, i.e. expression of CD1a and CD207 (langerin), was determined using flow cytometry. Cytogenetic analysis included GTG-banded metaphases and microarray (aCGH) evaluation. Furthermore, the morphology and ultrastructure of cells were evaluated using a confocal and scanning electron microscope. The microphotographs from the confocal imaging were used to reconstruct the mitochondrial network and its morphology. Basic cytophysiological parameters, such as viability, mitochondrial activity, and proliferation, were analyzed using multiple cellular assays, including Annexin V/7-AAD staining, mitopotential analysis, BrdU test, clonogenicity analysis, and distribution of cells within the cell cycle. Biomarkers potentially associated with histiocytoses progression were determined using RT-qPCR at mRNA, miRNA and lncRNA levels. Intracellular accumulation of histiocytosis-specific proteins was detected with Western blot. Cytotoxicyty and IC50 of vemurafenib and trametinib were determined with MTS assay.

RESULTS

Obtained cellular models, i.e. RAB-1, HAN-1, and CHR-1, are heterogenic in terms of molecular phenotype and morphology. The cells express CD1a/CD207 markers characteristic for dendritic cells, but also show intracellular accumulation of markers characteristic for cells of mesenchymal origin, i.e. vimentin (VIM) and osteopontin (OPN). In subsequent cultures, cells remain viable and metabolically active, and the mitochondrial network is well developed, with some distinctive morphotypes noted in each cell line. Cell-specific transcriptome profile was noted, providing information on potential new biomarkers (non-coding RNAs) with diagnostic and prognostic features. The cells showed different sensitivity to vemurafenib and trametinib.

CONCLUSION

Obtained and characterized cellular models of stromal-like cells derived from histiocytic lesions can be used for studies on histiocytosis biology and drug testing.

Langerhans cell histiocytosis of the head and neck in the pediatric population in a tertiary center: Clinical presentation, classification and treatment

INTRODUCTION

Langerhans cell histiocytosis (LCH) is a rare disease of unknown etiology with a heterogeneous and unspecific clinical presentation. Any organ or system may be involved but the most frequent is the skeleton. The diagnostic gold standard is done through histopathology combined with immunohistochemistry in the correct clinical setting. Treatment is still controversial. The objective of this study is to present a series of pediatric patients in order to contribute to the diagnosis and treatment of LCH.

MATERIAL AND METHODS

A longitudinal, descriptive and retrospective study was done in 20 pediatric patients histologically diagnosed of LCH int the last 10 years, in a tertiary center. A review of the medical history was done and data collection included: epidemiological data, clinical manifestations and classification, lesion characteristics, treatment employed, follow-up and evolution.

RESULTS

The mean age presentation was 6.5 years (2-12). The most frequent disease presentation was a palpable skull tumor followed by headache. Other otorhinolaryngologic presenting symptoms were bloody otorrhea and post auricular swelling. Single-systems LCH with skull tumors was the most frequent classification. Treatment options (surgery, chemotherapy and corticosteroid infiltration) were indicated according to disease classification.

CONCLUSION

LCH should be suspected in pediatric patients with a palpable cranial vault tumor, as well as in patients with chronic otorrhea with granulation tissue at the external ear canal. Management of LCH fundamentally includes chemotherapy and surgery, or the combination of both. High-risk organs lesions, including temporal bone lesions, and multi-system LCH are predictors of recurrence and should have a long-term follow-up.

Langerhans Cell Histiocytosis Associated With Underlying Hematolymphoid Disorders in Adults: Report of 2 Cases and Review of the Literature

Langerhans cell histiocytosis (LCH) is an uncommon disorder characterized by proliferation of abnormal LCs usually affecting children and adolescents. LCH in adults first presenting in the skin is rare. Although LCH and even LCH with a second malignancy may be more common in children, cutaneous LCH with a second hematologic malignancy has been more commonly identified in adults. The authors report 2 new cases of LCH in adult patients with underlying myelodysplasia and follicular lymphoma. The specimens were examined by routine microscopy and immunohistochemical stains for S100 protein and CD1a. Patients were elderly men with established diagnoses of follicular lymphoma and myelodysplasia, presented with follicular lesions and erythematous plaques involving intertriginous areas. Histologic examination revealed collections of mononuclear cells in upper dermis, which demonstrated strong positivity for S100 and CD1a, confirming their identity as LCs. BRAF analysis returned negative for detection of BRAF V600E mutation in both patients. The authors have recently encountered 2 cases of adult patients with skin-limited LCH predated by other lymphoproliferative disorders. The association between LCH and hematopoietic disorders may be explained by a common bone marrow precursor that is differentiating along different cell lines. Cutaneous LCH may be associated with underlying lymphoproliferative disorders and should be considered in the differential diagnosis of cutaneous eruptions in patients with hematopoietic disorders. Clinical follow-up evaluation of patients diagnosed with LCH for peripheral blood abnormalities and lymphadenopathy or "B symptoms" may be prudent in patients not already carrying a diagnosis of an underlying hematologic disorder.

Insights into the pathogenesis of Langerhans cell histiocytosis: the development of targeted therapies

More than a century after its first description, Langerhans cell histiocytosis (LCH) still remains an intriguing disease. Considerable progress in understanding its biology has been achieved recently. Description of the V600E BRAF mutation in samples of LCH tissue in 2010 was followed by description of additional mutations, all leading to constitutive ERK activation. Current experimental data suggest that LCH is a myeloid neoplasia with inflammatory properties, yet the exact pathophysiology remains poorly understood. Disease management paradigms have changed over time, closely reflecting the evolving view of the nature of the disease. The international Histiocyte Society have conducted three prospective clinical studies on multisystem LCH since the early 1990s. The standard frontline therapy for patients with multisystem LCH based on the cumulative knowledge of those trials consists of 6–12 weeks of initial therapy (daily oral steroids and weekly vinblastine injections), followed by pulses of prednisolone/vinblastine every 3 weeks, for a total treatment duration of 12 months. A currently ongoing study (LCH-IV) with a complex design (five interventional and two observational strata) targets further reduction of mortality and morbidity by tailoring treatment intensity depending on expected risk, as well as by exploring treatment regimens for special locations. Current knowledge on LCH pathobiology opens opportunities for improvement in the patient outcome. The activating BRAF and MAP2K1 mutations collectively accounting for about 75% of the LCH population as well as the resulting constitutive activation of downstream ERK offer an opportunity for targeted treatment. Related issues (eg, finding most effective and less toxic drugs or combinations, appropriate dosage, and optimal treatment duration) must be addressed in controlled prospective trials. Additional mechanisms, such as the interactions of the mutated dendritic cell clone with other inflammatory cells and key cytokines and chemokines, still remain attractive targets for therapeutic intervention, particularly in patients with localized, less aggressive disease.

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.

Genomic Alterations in Langerhans Cell Histiocytosis

The discovery of recurrent somatic genomic alterations in Langerhans cell histiocytosis (LCH) has led to a new understanding of LCH as a clonal neoplastic disorder. Most of the abnormalities described to date affect the RAS/RAF/MEK/extracellular-signal-regulated kinase (ERK) pathway: more than 50% of LCH cases carry activating mutations in BRAF, whereas another 10% to 28% carry activating mutations of MAP2K1, which encodes MEK1. The pathogenetic importance of these mutations has been confirmed by reports of significant clinical responses to RAF inhibitors.

Langerhans cell histiocytosis: a comprehensive review

Langerhans cell histiocytosis (LCH) is currently regarded as a myeloid neoplasm, with remarkably broad clinical spectrum, ranging from isolated skin or bone lesions to a disseminated disease that can involve nearly any organ. LCH is generally regarded as a sporadic disease that occurs predominantly in the paediatric population. The diagnosis of LCH is confirmed by immunohistochemistry (IHC) by demonstrating the presence of dendritic cell markers such as S100 protein, in addition to CD1a and langerin. Contrary to previous beliefs, recent literature reveals that the pathogenesis of LCH might involve a clonal process implicating BRAF c.1799T>A (p.Val600Glu) and other mutations [(600DLAT) B-RAF and (T599A) B-RAF, somatic MAP2K1 mutations].Through this review article, we have summarised the latest understanding of the biological and salient histological characteristics of LCH and its potential morphological mimics.

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.

New insights into the molecular pathogenesis of langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is a rare proliferative disorder characterized by an accumulation of cells sharing the major phenotypic features of cutaneous Langerhans cells. Given its variable clinical evolution, ranging from self-limiting lesions to multisystemic forms with a poor prognosis, in the last decades it has been debated whether LCH might not have a neoplastic rather than an inflammatory nature. However, although the fundamental events underlying the pathogenesis of LCH are still elusive, recent advances have strikingly improved our understanding of the disease. In particular, the identification of multiple interplays between LCH cells and their tumor microenvironment, along with the recognition of the lesional cytokine storm as a key determinant of LCH progression, has substantiated new opportunities for devising targeted therapeutic approaches. Strikingly, the detection of the rapidly accelerated fibrosarcoma isoform B(V600E) gain-of-function mutation as a genetic alteration recurring in more than 50% of patients has fueled the paradoxical picture of LCH as a tumor of the antigen-presenting cells that can evade rejection by the immune system. Thus, new evidence regarding the ontogeny of LCH cells, as well as a better understanding of the putative immune system frustrating strategy in LCH, may help to define the precise pathogenesis.

Biological and therapeutic implications of the BRAF pathway in histiocytic disorders

Langerhans cell histiocytosis (LCH) has historically evolved in its classification from a primary immune dysregulatory disorder to what current evidence supports as a dendritic cell neoplasm with an immune-inflammatory component. A key part of the classification of LCH as a neoplasm has been the identification of BRAF V600E mutations in 35% to 60% of cases. Tumor protein p53 (TP53) and RAS mutations have also been identified, albeit in less than 2% of reported cases. Of note, over 50% of patients with another dendritic cell disease, Erdheim-Chester Disease, have also been shown to have BRAF V600E mutations. Although the BRAF mutations have not been shown to be associated with extent of disease, they may still provide a target for a molecularly guided approach to therapy. In cases of LCH in which no BRAF mutations were identified, there was evidence for activation of the RAS-RAF-MEK-extracellular signal-regulated kinases (ERK) pathway, suggesting that similar to other tumors, this pathway may be therapeutically exploitable. Anecdotal responses have been reported in a few patients with LCH and Erdheim-Chester Disease to vemurafenib, a BRAF V600E inhibitor. Although these results pave the way for careful, prospective clinical testing, selection of the optimal groups in which to test such inhibitors, alone or in combination, will be critical based on the toxicity profile thus far observed in adults with melanoma and other BRAF mutated tumors.

Pulmonary Langerhans cell histiocytosis: profiling of multifocal tumors using next-generation sequencing identifies concordant occurrence of BRAF V600E mutations

BACKGROUND

Pulmonary Langerhans cell histiocytosis is a localized proliferation of Langerhans cells in the lung that presents without systemic manifestations as bilateral nodular lung disease in adult cigarette smokers. The molecular basis for this proliferation is unknown.

METHODS

Twenty-two concurrent nodules in five patients were microdissected from formalin-fixed paraffin-embedded tissue and analyzed by next-generation sequencing for mutations in 46 cancer genes with the Ion AmpliSeq Cancer Panel on an Ion PGM (Personal Genome Machine) Sequencer (Life Technologies Corporation). Mutation confirmation was performed by conventional Sanger sequencing or by sensitive coamplification at lower denaturation polymerase chain reaction/fluorescence melting curve analysis.

RESULTS

Small amounts of DNA (10 ng) isolated from nodules were sufficient for successful interrogation of 740 mutational hot spots in 46 cancer genes by the Ion PGM Sequencer, with an average depth of coverage of 2,783 reads per hot spot and with uniformity of coverage of 92%. BRAF V600E mutation was detected in all concurrent nodules studied in two of the five patients, whereas in three of the five patients, no oncogene mutations were found.

CONCLUSIONS

Pulmonary Langerhans cell histiocytosis appears to be a clonal proliferation that may or may not have BRAF V600E mutations. For those with BRAF V600E mutations, new targeted therapies, such as vemurafenib, may be used in progressive cases.

An exploratory epidemiological study of Langerhans cell histiocytosis

We explored potential risk factors associated with Langerhans cell histiocytosis (LCH) in a predominantly Hispanic population in Los Angeles. Sixty children with LCH (cases) and, 150 randomly selected patients (controls) were interviewed. There was no statistically significant difference between cases and controls in the following: Family history of thyroid disease, smokers in the family, maternal problems during pregnancy, and pesticide exposure. Cases were more likely to report a family history of cancer (OR 2.5), infection during infancy (OR 2.76), and parental occupational exposure to metal, granites, or wood dust (OR 2.48).

Use of the JL1 epitope, which encompasses the nonglycosylation site of CD43, as a marker of immature/neoplastic Langerhans cells

Langerhans cell histiocytosis (LCH) is the collective designation for a group of proliferative disorders of antigen-presenting cells in the epidermis. Over the past several decades, the etiology of LCH has been a controversial issue, particularly with respect to the pathologic process, that is, whether it is a neoplastic or inflammatory process. Recently, it was reported that the JL1 epitope, which encompasses the nonglycosylation site of CD43, is only exposed in the precursor stages of hematopoietic cells or in neoplastic conditions. We sought to investigate the possible utility of the JL1 monoclonal antibody as a diagnostic marker of LCH. In this study, we compared the staining characteristics of antibodies against the JL1 epitope with those of langerin and CD1a, which are widely used for the diagnosis of LCH. We found substantial differences in the staining patterns of these markers. The JL1 epitope could be bound by antibodies in cases of LCH and Langerhans cell (LC) sarcoma. In non-neoplastic lesions, JL1-positive LCs were found only in dermatitis, reflecting the immaturity of LCs in inflamed skin. However, anti-langerin antibodies were able to identify any form of LC, including those in normal skin, dermatitis, dermatopathic lymphadenopathy, and LCH. On the basis of these findings, we propose that the anti-JL1 antibody is a specific marker of immaturity, a feature that is shared in neoplastic LCs, and can be useful in the diagnosis of LCH.

Langerhans cell histiocytosis of bone in children: a long-term retrospective study

Langerhans cell histiocytosis is rare and frequently involves the bone. We retrospectively reviewed the orthopaedic aspects (symptoms, localizations, treatments) and the long-term outcome [disease status, overall survival (OS), event-free survival (EFS)] of 121 patients (June 1968-December 2009). The main symptom was local pain. The orthopaedic treatment was mainly conservative. The most frequent localization was osseous monofocal (62% of monosystemic diseases). Monosystemic and osseous monofocal localizations, treatment after 1991 (OS, P=0.007; EFS, P=0.03) and age older than 2 years (OS, P=0.003; EFS, P=0.001) were prognostic factors that were positively associated with survival. Oncologic treatment has improved over time, translating into better survival. A biopsy is often mandatory.

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.

Langerhans cell histiocytosis: 40 years' experience

OBJECTIVES

Our study analyzes 40 years' experience with pediatric Langerhans cell histiocytosis patients.

MATERIALS AND METHODS

Between June 1968 and December 2009, 121 patients (79 males, 42 females; median age 4.13 y) were diagnosed at our center (74% monosystemic disease; 26% multisystemic), treated according to current protocols. We evaluated the response, the survival, and the neuroendocrinological sequelae.

RESULTS

Overall survival (OS) for all patients was 93% at 10 years from diagnosis, event-free survival (EFS) 77%. OS for patients younger than 2 years and older than or equal to 2 years was 82% and 97% (P = 0.003); EFS 48% and 87% (P = 0.001). OS for patients diagnosed before and after April 1, 1991 was 84% and 98% (P = 0.007), EFS 66% and 85% (P = 0.03). OS for monosystemic and multisystemic disease was 100% and 71% (P < 0.001); EFS 88% and 45% (P < 0.001). OS for "risk" patients (involvement of bone marrow, spleen, liver, lungs) and "low-risk" patients was 50% and 94% (P = 0.007), EFS 37% and 54% (P = 0.06). Fourteen patients developed diabetes insipidus, 7 patients growth hormone deficiency, 2 hypothyroidism, and 1 neurodegeneration.

CONCLUSIONS

Our study confirms improvement of pathogenetic knowledge and treatment over the last 20 years. Age at diagnosis older than or equal to 2 years and standardized treatment are associated with improved prognoses. Multisystemic involvement, especially with "risk" organs seem to be correlated to a worse outcome.

Recent advances in the understanding of Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is a proliferative disease of cells that share phenotypic characteristics with the primary antigen presenting cells of the epidermis. Its clinical manifestations are highly variable, extending from very benign forms to a disseminated, aggressive disease that causes significant mortality. Although many of the fundamental pathogenetic features of LCH have been enigmatic, recent advances have led to a much clearer understanding of the disease. In particular, careful molecular analyses of mouse models and human LCH samples suggest that LCH's cell of origin may not be the epidermal LC itself but a myeloid-derived precursor. Advanced genomic technologies have revealed the presence of activating, somatic BRAF mutations in the majority of patient specimens. Together, these observations have produced a new picture of LCH as a myeloid neoplasm. These advances are likely to have profound implications for the use of targeted therapeutics in LCH.

New clinical score for disease activity at diagnosis in Langerhans cell histiocytosis

BACKGROUND

The clinical presentation and course of Langerhans cell histiocytosis (LCH) are variable, ranging from an isolated, spontaneously remitting bone lesion to multisystem disease with risk organ involvement. Treatment of LCH ranges from a wait-and-see attitude to intensive multidrug therapy and, in some cases, bone marrow transplantation. It is necessary to develop an objective score for assessing disease activity in patients with LCH. We propose a new clinical scoring system to evaluate disease activity at diagnosis that can predict the clinical outcomes of LCH and correlate it with clinical courses.

METHODS

Clinical data, obtained from children diagnosed with LCH at Asan Medical Center and Hanyang University Hospital between March 1998 and February 2009, were studied retrospectively. The scoring system was developed according to the basic biological data, radiological findings, and physical findings and applied to a database containing information on 133 patients.

RESULTS

The median age of the 133 patients (74 male, 59 female) was 52 months (range, 0.6-178 months), and LCH was diagnosed based on CD1a positivity. At diagnosis, the score distributions were highly asymmetrical: the score was between 1 and 2 in 75.9% of cases, 3-6 in 15.8%, and greater than 6 in 8.3%. Initial scores above 6 were highly predictive of reactivation and late complications.

CONCLUSION

This new LCH disease activity score provides an objective tool for assessing disease severity, both at diagnosis and during follow-up.

Langerhans cell histiocytosis: Current concepts and treatments

Langerhans cell histiocytosis (LCH) is a rare proliferative disorder of cells with the phenotype of activated Langerhans cells. The diagnosis of LCH is often delayed or missed. Many questions about LCH remain to be answered, including whether it is caused by a malignancy or by immune dysregulation. Data from the early 1990s showed that LCH consisted of an accumulation of monoclonal LCH cells, suggesting a neoplastic disorder. However, further investigations with current sophisticated techniques have not shown consistent genomic aberrations. Recent data which suggests a role for an IL-17A dependant pathway of dendritic cell fusion in LCH remains to be proven. The most recent data taken together swing the pendulum towards an immunologic aberration. The clinical course of LCH is highly variable, ranging from a self-healing solitary bone lesion to widely disseminated life-threatening disease. Patients with multisystem (MS) disease with organ dysfunction, particularly those refractory to front line therapy, and those with multiple reactivations of disease associated with significant permanent sequelae represent the greatest challenge. Early switch of refractory patients to salvage therapies has contributed to the improvement in survival of MS-LCH patients. Due to the rarity of LCH in children and adults, patients must be enrolled on multi-national clinical trials, whenever possible, to advance our knowledge of the optimal therapeutic strategies and long-term outcomes.

Langerhans cell histiocytosis: malignancy or inflammatory disorder doing a great job of imitating one?

Langerhans cell histiocytosis (LCH) is the unifying designation for a rare proliferative disorder that occurs predominantly in childhood and involves the main antigen-presenting cell of the epidermis. LCH can present in a multitude of ways, from a self-limited rash that resolves spontaneously to a systemic multi-organ disease with a 20% mortality rate. Because some forms behave in a relatively benign manner and are associated with an inflammatory cell infiltrate, it has been proposed that LCH might be a reactive disease. However, its neoplastic nature is suggested by the fact that the proliferating cells in LCH are clonal and overexpress p53. Nonetheless, no recurrent genomic, genetic or epigenetic abnormalities have been identified. Instead, a variety of molecular abnormalities that are consistent with disordered Langerhans cell maturation have been described. A faithful small animal model would aid our understanding of the pathophysiology of LCH but, to date, none exists. Challenges to the creation of a model include the lack of characteristically recurrent genetic abnormalities and the absence of a truly tissue-specific promoter to drive expression of genetic elements solely in Langerhans cells. Still, some of the phenotypic abnormalities in adhesion molecule or chemokine receptor expression might be modeled with sufficient precision to allow the testing of novel therapies.

Small cell tumors of bone

Bone tumors are fortunately rare, but small cell tumors of bone are a relatively common subset of these lesions. They comprise of a diverse group of primary and metastatic neoplasms in both children and adults. The most common small cell tumors of bone include Ewing sarcoma/primitive neuroectodermal tumor, small cell osteosarcoma, multiple myeloma, lymphoma, leukemia, neuroblastoma, rhabdomyosarcoma, and Langerhans cell histiocytosis. Although each entity has its distinctive features, the differential diagnosis of this group of tumors is still challenging because they are all "small, blue, and round cell tumors", histologically. The correct diagnosis of small cell tumors of bone depends on an evaluation of clinical, radiologic, pathologic, and genetic features. Patients' age and sex are very important, as are the signs and symptoms at presentation. Radiologically, which bone is involved, the specific portion of the bone (epiphysis, metaphysis, or diaphysis; cortex vs. medulla) involved, and the radiographic manifestations (lytic, blastic, or mixed lytic and blastic) are also often critical parameters for the diagnosis. In recent years, with a better understanding of the molecular and cytogenetic background of several small cell tumors, more accurate diagnoses have been supported by the clinicopathologic criteria and by a panel of immunohistochemical studies. In this review we will provide an overview of the clinical, radiologic, pathologic, and genetic characteristics of these tumors.

No genomic aberrations in Langerhans cell histiocytosis as assessed by diverse molecular technologies

The etiology of Langerhans cell histiocytosis (LCH), a disease characterized by uncontrolled proliferation of Langerhans cells, is unknown. Although some believe that LCH is reactive, others support a neoplastic origin. We tested the hypothesis that LCH is neoplastic by investigating potential consistent chromosomal aberrations in LCH cells. We used multiparameter DNA flow cytometry to analyze the DNA ploidy LCH cells in 20 cases, performed karyotype analysis in 31 cases, array-based comparative genomic hybridization (arrayCGH) and single nucleotide polymorphism (SNP) arrays with DNA from flow-sorted CD1a-positive and CD1a-negative cells in 19 cases. Ploidy analysis revealed diploid DNA content in all cases. The karyotype of all patients analyzed was normal, excluding the presence of balanced translocations. ArrayCGH and SNP arrays did not show genome abnormalities. Despite positive TP53 protein immunohistochemical staining, sequencing of exon 5 to 8 of p53 gene showed no alterations in 7 cases. This study strongly suggests that gross chromosomal abnormalities do not cause LCH. Although we cannot exclude cryptic point mutations in as yet unidentified genes, this study of 72 LCH cases shows that LCH may be the result of restricted oligoclonal stimulation rather than unlimited neoplastic proliferation. (c) 2008 Wiley-Liss, Inc.

IL-1 beta and PGE2 levels are increased in the saliva of children with Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is a rare disorder mainly of children, whose pathogenesis is still unknown. Some studies have demonstrated that LCH lesions produce different cytokines abnormally that may be relevant to the pathogenesis of the disease. The purpose of this study was to investigate interleukin-1 beta (IL-1 beta) and prostaglandin E2 (PGE(2)) levels in saliva from children with different clinical subtypes of LCH. We studied 29 children with LCH: seven unifocal (Group I), seven multifocal (Group II), 15 multisystemic (Group III) and 12 healthy volunteers (Group IV). Salivary IL-1 beta and PGE(2) levels were significantly higher in LCH than in normal children. A multi-comparison test showed significantly (P < 0.001) higher levels of both IL-1 beta and PGE(2) in saliva from Group III compared with Groups II and I. A significant correlation (r = 0.05) between IL-1 beta and PGE(2) concentrations in saliva from each group was determined. Our findings demonstrated an association between high concentrations of salivary IL-1 beta and PGE(2) and advanced stages of the disease. This allows us to suggest that the abnormal amount of these factors in saliva may serve as a risk marker for disease progression.

Langerhans cell histiocytosis: update for the pediatrician

PURPOSE OF REVIEW

Langerhans cell histiocytosis is the commonest of the histiocytic disorders. Owing to the relative rarity of the condition, it remains a disease in which the diagnosis is often delayed or missed and in which many questions remain unanswered, ranging from etiology and pathogenesis to therapy. The management is often frustrating for care-givers and parents/patients. The purpose of the review is therefore to raise awareness of the disease and to highlight the clinical findings that should make the pediatrician or primary care-giver suspect the diagnosis, as well as current thinking regarding management of the various and diverse manifestations of this disease.

RECENT FINDINGS

We discuss new and interesting insights into the biology of Langerhans cell histiocytosis that raise the possibility of future targeted therapy. Important points in the diagnosis, investigation and management of the various forms of the disease are also discussed.

SUMMARY

We present a review of childhood Langerhans cell histiocytosis, highlighting new insights into pathogenesis and management of the various forms of this complex disease.

Telomere length shortening in Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is a clonal, proliferative disorder of phenotypically immature CD1a(+) Langerhans cells (LC). The aetiology of LCH is unknown and data supporting an immune dysregulatory disorder as well as a clonal neoplasm have been reported. Telomere shortening has been associated with cancers and premalignant lesions as well as promoting chromosomal instability. To determine whether LCH LC have altered telomere lengths, we used dual detection of CD1a expression by immunofluorescence and telomere length by fluorescence in situ hybridization of LCH LC and lymphocytes in local, multisystem and systemic LCH and compared these with telomere lengths of LC and lymphocytes in reactive lymph nodes. LCH LC showed significantly shorter telomere lengths than LC from reactive lymph nodes or unaffected skin. Lymphocyte telomere lengths showed similar profiles among the different samples. These data show a significant telomere shortening in LCH LC in all stages of disease involvement compared with LC from reactive lymph nodes, suggesting that LCH may share mechanisms of telomere shortening and survival with clonal preneoplastic disorders and cancer, although an initiating infectious or immune event is still possible.

Expansion of regulatory T cells in patients with Langerhans cell histiocytosis

BACKGROUND

Langerhans cell histiocytosis (LCH) is a rare clonal granulomatous disease that affects mainly children. LCH can involve various tissues such as bone, skin, lung, bone marrow, lymph nodes, and the central nervous system, and is frequently responsible for functional sequelae. The pathophysiology of LCH is unclear, but the uncontrolled proliferation of Langerhans cells (LCs) is believed to be the primary event in the formation of granulomas. The present study was designed to further investigate the nature of proliferating cells and the immune mechanisms involved in the LCH granulomas.

METHODS AND FINDINGS

Biopsies (n = 24) and/or blood samples (n = 25) from 40 patients aged 0.25 to 13 y (mean 7.8 y), were studied to identify cells that proliferate in blood and granulomas. We found that the proliferating index of LCs was low ( approximately 1.9%), and we did not observe expansion of a monocyte or dendritic cell compartment in patients. We found that LCH lesions were a site of active inflammation, tissue remodeling, and neo-angiogenesis, and the majority of proliferating cells were endothelial cells, fibroblasts, and polyclonal T lymphocytes. Within granulomas, interleukin 10 was abundant, LCs expressed the TNF receptor family member RANK, and CD4(+) CD25(high) FoxP3(high) regulatory T cells (T-regs) represented 20% of T cells, and were found in close contact with LCs. FoxP3(+) T-regs were also expanded compared to controls, in the blood of LCH patients with active disease, among whom seven out of seven tested exhibited an impaired skin delayed-type hypersensitivity response. In contrast, the number of blood T-regs were normal after remission of LCH.

CONCLUSIONS

These findings indicate that LC accumulation in LCH results from survival rather than uncontrolled proliferation, and is associated with the expansion of T-regs. These data suggest that LCs may be involved in the expansion of T-regs in vivo, resulting in the failure of the host immune system to eliminate LCH cells. Thus T-regs could be a therapeutic target in LCH.

Differences in telomerase expression by the CD1a+ cells in Langerhans cell histiocytosis reflect the diverse clinical presentation of the disease

Langerhans cell histiocytosis (LCH) is a disease characterized by an uncontrolled clonal proliferation of Langerhans cells, whose aetiology is still unclear. The clonal nature of LCH could support the hypothesis that it is a neoplastic disease with unlimited growth potential. One requirement for unlimited proliferation is the maintenance of telomere length. In a group of 70 patients, we set out to investigate whether a telomere maintenance mechanism is indeed active in LCH cells. This work showed that LCH cells from all restricted skin LCH lesions (6/6) expressed telomerase as assessed by human telomere reverse transcriptase (hTERT) immunohistochemistry, whereas LCH cells from the majority of the bone lesions analysed did not express hTERT (26/34). Interestingly, in contrast to the solitary bone lesions, LCH cells from lesions of multi-system patients always expressed telomerase (11/11), regardless of the lesional site. In situ telomeric repeat amplification protocol (TRAP) assays performed on different lesional sites showed that this telomerase was active. In addition, the telomere length of LCH cells from a hTERT-positive skin multi-system lesion was long and homogeneous when compared to that in the LCH cells from hTERT-negative bone single-system LCH lesions, which was heterogeneous in length. No evidence for an alternative lengthening of telomeres mechanism was found in hTERT-negative lesions. The difference in telomerase expression and telomere length at the different lesional sites and in biopsies from patients with solitary versus multi-system disease appears to reflect the diverse clinical presentation and course of this disease. The results from this study have important implications for understanding the nature of this disease.

Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is a complex disease entity comprised of three distinct clinical syndromes that demonstrate indistinguishable histology. These syndromes are: eosinophilic granuloma, which is predominantly osseous or pulmonary; Hand-Schûller-Christian's disease, which involves multiple organ systems and, most typically, the skull base; and Letterer-Siwe's disease, the most severe disease manifestation, which typically involves the abdominal viscera. This article reviews our current understanding of Langerhans cell histiocytosis by discussing the history, histology, etiology, and treatment of the disease. It focuses on the radiographic findings and imaging modalities that are the most useful in disease diagnosis and management.

Oral Manifestations of Langerhans Cell Histiocytosis in a Pediatric Population

Langerhans Cell Histiocytosis is a rare and protean disease of unknown etiology, clinically characterized by single or multiple osteolytic and/or soft tissue lesions. Oral involvement may predate systemic manifestations or mimic infectious/inflammatory disorders. In the present series, oral involvement characterized eight cases of pediatric Langerhans Cell Histiocytosis and oral symptoms represented a very early sign of this disease in four patients. A careful clinical investigation and a proper histologic analysis were required for achieving a definite diagnosis and for confirming clinical suspicion of disease relapse. Immunohistochemistry, that nowadays represents a reliable and accessible ancillary histological technique, allowed the definite diagnosis in all cases of our series.

Solitary congenital self-healing reticulohistiocytosis in monozygotic twins

We report monozygotic twins with congenital self-healing reticulohistiocytosis, whose lesions initially presented as hemorrhagic bullae at birth with rapid progression into crusted papules the following day. Physical examination disclosed crusted papules on the right side of the neck of twin 1 and a similar solitary lesion on the lateral side of the right thumb of twin 2. Excisional biopsy specimen findings of the neck and thumb lesions were consistent with Langerhans cell histiocytosis, which was further confirmed by positive CD1a staining. The lesions resolved completely by 2 months with no evidence of recurrence or systemic involvement. Congenital self-healing reticulohistiocytosis is a rare, self-limited form of Langerhans cell histiocytosis. Although familial clustering in Langerhans cell histiocytosis was previously reported, to the best of our knowledge there is no report suggesting familial clustering in congenital self-healing reticulohistiocytosis. Our patients are interesting in terms of raising the question of whether the presence of congenital self-healing reticulohistiocytosis in monozygotic twins is implicative of a genetic role in its pathogenesis.

An enigmatic disease: childhood Langerhans cell histiocytosis in 2005

Histiocytic proliferative diseases, although rare, constitute a challenge for pediatric pathologists and hematologists/oncologists because of difficulties in the identification of subtypes and the lack of established standard therapies, resulting in treatment failures, recurrences, or complications. Amongst the different types of such disorders, Langerhans cell histiocytosis (LCH) has been enigmatic to all involved, secondary to a long list of unresolved issues in pathogenesis and treatment. The fundamental dispute over its neoplastic vs. reactive nature remains unsettled. Unique features of LCH, including clonality, cases with spontaneous regression, frequent recurrences, and target tissue/organ tropism, have attracted significant interest. This article reviews the current understanding of LCH in the light of discoveries over the last few decades.

Langerhans cell histiocytosis and human herpes virus 6 (HHV-6), an analysis by real-time polymerase chain reaction

Patients with Langerhans cell histiocytosis (LCH) usually present to orthopedic surgeons because this disease most commonly affects bone. The pathogenesis of LCH is unknown, although roles for environmental, infectious, immunologic, and genetic causes have been postulated. More specifically, there is limited data suggesting that human herpes virus 6 (HHV-6) may be a potential etiologic agent. Frozen biopsy material was obtained from 13 patients with LCH and 20 patients without the disease. After ensuring histologic adequacy of the material, the tissue was tested for HHV-6 by qualitative and quantitative real-time TaqMan PCR. Four of 13 patients with LCH had evidence of HHV-6 DNA in their tissue while 7 of 20 control patients tested positive for HHV-6 genome. Viral loads are reported for the positive patients; no statistical difference was observed in the presence or quantity of HHV-6 DNA found in either population, suggesting that the prevalence of HHV-6 in the tissue of LCH patients is the same as that found in tissue from individuals without disease.

Langerhans cell histiocytosis: current insights in a molecular age with emphasis on clinical oral and maxillofacial pathology practice

Langerhans cell histiocytosis (LCH) commonly involves the oral and maxillofacial region, and comes to the attention of dental practitioners when a patient presents with orofacial pain and a bony or soft tissue lesion. This is a relatively rare entity, which has made it difficult to investigate the clinical, biologic, and molecular aspects of the disease. Treatment protocols are not well defined, particularly in adults. During the past decade, the Histiocyte Society has formulated various LCH categories, based on risk stratification, and treatment protocols for the pediatric population. Adult trials are currently available through the Histiocyte Society. Although there has been considerable controversy, the neoplastic nature of LCH has been established by demonstrating clonality. LCH symptoms and the development and persistence of LCH lesions have been ascribed to a "chemokine/cytokine storm" due to autocrine and paracrine mechanisms. Discovery of biologic, cytogenetic, and molecular abnormalities in LCH have already affected treatment by providing novel therapeutic targets.

Langerhans cell histiocytosis associated with myelodysplastic syndrome in adults

BACKGROUND

Myelodysplastic syndrome (MDS) is a group of bone marrow disorders associated with dyplasia of myeloid elements that may have cutaneous manifestations including infections, vasculitis, Sweet's syndrome, pyoderma gangrenosum, erythema elevatum diutinum, and leukemia cutis. These cutaneous manifestations are attributed to the underlying bone marrow defect. Langerhans cell histiocytosis (LCH) is primarily a pediatric disease, and rarely LCH has been described in association with pediatric MDS. We are aware of only a single case report of LCH associated with MDS in an adult.

METHODS

We report two new cases of LCH in elderly patients with underlying MDS. The specimens were examined by routine microscopy as well as immunohistochemical stains for S100 protein and CD1a.

RESULTS

Both patients were elderly men with established diagnoses of MDS. One presented with a solitary pruritic papule while the other had a 2-year history of erythematous papules involving the trunk and extremities. Histologic examination revealed intraepidermal and dermal collections of mononuclear cells with reniform nuclei. The cells were strongly positive for S100 and CD1a, confirming their identity as Langerhans cells.

CONCLUSION

Cutaneous LCH may be associated with underlying MDS in adults and should be considered in the differential diagnosis of cutaneous eruptions in patients with MDS.

Biology of Langerhans cells and Langerhans cell histiocytosis

Langerhans cells (LC) are epidermal dendritic cells (DC). They play an important role in the initiation of immune responses through antigen uptake, processing, and presentation to T cells. Langerhans cell histiocytosis (LCH) is a rare disease in which accumulation of cells with LC characteristics (LCH cells) occur. LCH lesions are further characterized by the presence of other cell types, such as T cells, multinucleated giant cells (MGC), macrophages (MPhi), eosinophils, stromal cells, and natural killer cells (NK cells). Much has been learned about the pathophysiology of LCH by studying properties of these different cells and their interaction with each other through cytokines/chemokines. In this review we discuss the properties and interactions of the different cells involved in LCH pathophysiology with the hope of better understanding this enigmatic disorder.

The role of vascular endothelial growth factor in Langerhans cell histiocytosis

In angiogenesis, new blood vessels are generated from pre-existing ones. It plays a major role in tumor growth and metastasis. The main pro-angiogenic factor is the vascular endothelial growth factor (VEGF). VEGF displays high specificity for vascular endothelial cells and also elicits a pronounced angiogenic response in a variety of in vivo models. VEGF withdrawal has been shown to result in regression of vasculature in tumors. The pathogenic and the angiogenic processes of Langerhans cell histiocytosis (LCH) are not yet clear. The purpose of this study was to investigate the extent of the angiogenic response in LCH tumors. The authors examined tissue sections from LCH patients with single lesion (5 patients) or multisystem disease (5 patients). The preparations were examined by using monoclonal anti-VEGF antibody, CD34, and factor VIII-like antigen. VEGF was expressed in 70% of the cases examined. All the multisystem lesions were positive, as were two of the five single-lesion tumors. LCH cells expressed VEGF. The blood vessel density was significantly higher within the lesion than in normal margins. The findings that VEGF was expressed in LCH cells and that all multisystem lesions were VEGF producers raise the possibility of using anti-angiogenic drugs to treat these patients. Further studies to explore the role of angiogenesis in LCH are warranted.

DOR-1, A novel CD10+ stromal cell line derived from progressive Langerhans cell histiocytosis of bone

BACKGROUND

Langerhans cell histiocytosis (LCH) is granulomatous proliferative disorder characterized by the presence of activated Langerhans cells admixed with macrophages, lymphocytes, and eosinophils. In an effort to obtain an LCH ex vivo model, we succeeded in establishing the DOR-1 cell line from an LCH lesion of bone in a 3-year-old girl.

PROCEDURE

The DOR-1 cell line was established from a CD1a immunoreactive LCH lesion of bone maintained in long-term cell culture. The phenotypic characteristics were assessed by immuno-cytochemistry and fluorescence activated cell sorter (FACS) analysis. Cytogenetic analysis was performed by RHG-banding that was supplemented by fluorescence in situ hybridization (FISH).

RESULTS

The DOR-1 cells grew in vitro as a poorly differentiated mesenchymal-like cells with a doubling time between 72 and 96 hr. The cells exhibited pleomorphism and consistent immuno-reactivity for CD10 (50%), CD13 (55%), CD68 (65%), and CD117 (70%) while CD1a, Langerin and HLA-DR were not detected. By RHG-banding, several aberrant chromosomes were detected including the t (9; 17) (p23; p13) translocation and a pair of long dicentric marker chromosomes indicating clonal abnormality. Functionally, exposure to 33 nM 12-O-tetradecanoyl phorbol mirystate-13-acetate (TPA) induced DOR-1 cell differentiation with appearance of cytoplasmic extensions.

CONCLUSIONS

The DOR-1 cell line exhibits distinct immuno-cytochemical features and carries the t (9; 17) (p23; p13) translocation suggesting involvement of stromal-like cell lineage in LCH initiation and progression.

Progressive form of pulmonary Langenharns' cell histiocytosis in a female adult non-smoker

Little is known about the cause, nature, treatment and prognosis of pulmonary Langerhans' cell histiocytosis (LCH) in adults. We report the case of a 44-year-old female non-smoker suffering from pulmonary histiocytosis who after a 7-year remission period relapsed with both lung and bone disease. Using a combination of corticosteroids, methotrexate and bone irradiation treatment, the patient achieved total disease remission. The patient was a non-smoking female who has had long-term and swift remission of the disease on two occasions.

Langerhans cell histiocytosis patients have HLA Cw7 and DR4 types associated with specific clinical presentations and no increased frequency in polymorphisms of the tumor necrosis factor alpha promoter

BACKGROUND

Current theory on the etiology of Langerhans cell histiocytosis (LCH), formerly Histiocytosis-X, is that abnormality(ies) of the immune system are responsible for dysregulation of Langerhans cells (LC) in patients' lesions. Among the known abnormalities in LCH patients are increased amounts of tumor necrosis factor alpha (TNF-alpha) and other cytokines in the lesions.

PROCEDURE

We investigated the human leukocyte antigen (HLA) phenotypes of 29 patients and 37 healthy family members to determine if any haplotypes segregate with the presence or locations of the disease. The lymphocyte subsets for 22 patients and 11 family members were also determined.

RESULTS

Patients with single bone, multiple bone, or multi-system LCH had different relative proportions of HLA types. Patients presenting with single bone disease had an especially high frequency of the DR4 type. In this patient group, every Caucasian patient had either Cw7 or DR4. Lymphopenia was documented in patients who had been off therapy as well as those who only had surgical curetage of their lesions. Family members also had low numbers of T lymphocytes. There were fewer mutations of the TNF-alpha promoter in patients than in the general population.

CONCLUSIONS

Although there is an increased percentage of LCH patients with DR4 and/or Cw7 there was also an increased prevalence of this antigen as well as lymphopenia among unaffected family members. Additional genetic and/or environmental factors are necessary to explain this association. TNF-alpha promoter mutations are not responsible for the increased production of this cytokine.

Maxillofacial manifestations of Langerhans cell histiocytosis: a clinical and therapeutic analysis of 10 patients

The definition of Langerhans cell histiocytosis (formerly known as histiocytosis X) includes the clinical syndromes Hand-Schueller-Christian syndrome, Abt-Letterer-Siwe syndrome, and eosinophilic granuloma. The paper gives an overview of current diagnostic and treatment strategies of LCH. Furthermore, records and clinical data of 10 patients with LCH were evaluated retrospectively. Patients' age ranged from 13 years to 42 years. The mandible was more frequently involved than the maxilla. Three patients (30%) had systemic manifestations of LCH in addition to their oral lesions. The longest follow-up period was 12 years. During follow-up six patients (60%) developed recurrent LCH and received adjuvant chemo- or radiation therapy. For solitary bone lesions, surgical curettage is the recommended treatment. Those patients with multi-organ involvement or recurrent LCH should be included into clinical trials initiated by the Histiocyte Society.

Expression of cell cycle-related gene products in Langerhans cell histiocytosis

BACKGROUND The pathogenesis of Langerhans cell histiocytosis (LCH), a disease characterized by an abnormal accumulation of the dendritic Langerhans cells, is still unknown. Based on the monoclonality of the CD1a+ cell and reports of familial clustering, it is hypothesized that a genetic alteration at a cellular level may be causative. This genetic change may have an effect on the cellular mechanisms controlling proliferation and apoptosis. MATERIALS AND METHODS LCH-lesions were studied for the expression of Ki-67, present in the nucleus of proliferating cells. Furthermore, the expression of cell cycle-related gene products TGF-beta receptor I and II, MDM2, p53, p21, p16, Rb, and Bcl2 were studied. The TGF-betaR genes play a role in tumor suppression, whereas Bcl2 inhibits apoptosis. The remaining genes are part of either the p53-p21 and/or p16-Rb pathways, which induce cell cycle arrest or apoptosis in response to DNA damage. RESULTS In 30 biopsies the diagnosis of LCH could be confirmed on the basis of CD1a positivity (27 bone and 3 skin). All cases showed scattered nuclear-positive staining for the proliferation marker Ki-67. In more than 90% (n >/=27) of these cases, expression of TGFbeta receptor I and II, MDM2, p53, p21, p16, Rb, and Bcl2 was detected in lesional LCH cells. The overexpression was in general heterogeneous, ranging from limited focal staining of scattered cells within the lesion to strong diffuse staining. CONCLUSIONS These findings suggest that the cellular mechanisms that sense and respond to DNA-damage, namely the p53-p21 pathway and the p16-Rb pathway, are activated. The expression of Ki-67 indicates that the cells in LCH are proliferating. The observed overexpression of Bcl2 may play a role in the activation of p53 and p16 and/or the arrest of apoptosis.

[Langerhans and non-Langerhans histiocytosis]

Although Langerhans cell histiocytosis (LCH) was described a century ago, its cause and pathogenesis are still unknown. A wide spectrum of disease and variable clinical behavior are characteristic. The clinical varieties of this enigmatic disease range from a lethal leukemia-like disorder that primarily affects infants to a curable solitary lytic lesion of bone. LCH is a clonal proliferative disorder of histiocytes that resembles in morphology and phenotype the dendritic antigen-presenting Langerhans' cells of the skin and other organs. Despite gaps in understanding, significant improvements in the therapies for this disease have been made. Careful risk stratification is critical for the appropriate administration of therapy. Patients with good prognostic factors may need only observation as their disease spontaneously regresses, or minimal intervention. The active search for more effective treatments for patients with poor prognostic features is a major future challenge for the Histiocyte Society.

Langerhans cell histiocytosis with transformation to acute leukemia showing 45,X, t(8; 21), 5q-, -Y karyotype

A 31 -year-old man was admitted to hospital with onset of difficulty in walking and urinary incontinence, leading to the diagnosis of Langerhans cell histiocytosis (LCH) which was replacing a thoracic vertebra. Four months after the completion of radiation therapy, he was referred to our department with persistent fever and severe pyogenic ulceration mainly affecting the right-hip. A diagnosis of acute non-lymphoblastic leukemia (ANLL) was made. Cytogenetic studies showed 45,X, t(8; 21), 5q-, -Y We report this case because, development of acute leukemia after LCH is rare and the literature searched for any cytogenetic study in these kind of cases yielded no data.