Analysis of loss of heterozygosity in single-system and multisystem Langerhans' cell histiocytosis

Genomic Alterations in Langerhans Cell Histiocytosis

Langerhans cell histiocytosis (LCH) is a myeloid neoplastic disorder characterized by inflammatory lesions with clonal histiocytes. LCH is driven by activating mitogen-activated protein kinase (MAPK) pathway mutations. BRAFV600E is the most common mutation and is associated with more extensive disease at presentation and risks of front-line treatment failure, liver disease, and LCH-associated neurodegeneration. Genetic ancestry influences LCH with highest incidence in Hispanic populations. MAPK inhibitors are effective, but do not achieve cure in most cases. Clinical trials prospectively testing risk-stratification based on somatic mutation and/or detectable mutation in peripheral blood may improve outcomes for LCH patients.

Cervical langerhans cell histiocytosis mimicking cervical tuberculosis: A Case report

RATIONALE

Langerhans cell histiocytosis (LCH) involving adult cervical vertebrae is relatively rare clinically.

PATIENT CONCERNS

An 18-year-old male patient exhibited a 1-month history of neck pain, restricted neck mobility, and numbness and weakness of both upper limbs. The patient reported no pain at other sites, exhibited no fever or night sweats, and was unable to recall any recent injury.

DIAGNOSES

On the basis of the radiological features of the lesion and laboratory tests, there was a high possibility that the patient had a tuberculosis lesion. Postoperative GeneXpert and Mycobacterium tuberculosis (MTB) culture results showed MTB negative. Postoperative pathological results showed: (Cervical 4 vertebrae) LCH.

INTERVENTIONS

Our department did an anterior approach operation. The patient was treated with prednisone combined with vincristine after operation.

OUTCOMES

The patient was discharged from the hospital with complete remission of cervical pain and rapid relief of neurological symptoms.

LESSONS

Computed tomography-guided biopsy of lesion tissue must be performed when a suspected infection occurs in young patients. If possible, the lesion tissue obtained during the operation should be cultured and pathologically examined for early diagnosis.

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.

[Pulmonary Langerhans cell histiocytosis]

Pulmonary Langerhans cell histiocytosis is regarded as a reactive proliferation of the dendritic Langerhans cell population stimulated by chronic tobacco-derived plant proteins due to incomplete combustion but can also occur in childhood as a tumor-like systemic disease. Currently, both these forms cannot be morphologically distinguished. In the lungs a nodular proliferation of Langerhans cells occurs in the bronchial mucosa and also peripherally in the alveolar septa with an accompanying infiltration by eosinophilic granulocytes and destruction of the bronchial wall. Langerhans cells can be selectively detected with antibodies against CD1a and langerin. In the reactive isolated pulmonary form, abstinence from tobacco smoking in most patients leads to regression of infiltration and improvement of symptoms. In high-resolution computed tomography (HRCT) the small star-like scars can still be detected even after complete cessation of tobacco smoking.

Langerhans cell histiocytosis with multisystem involvement in an infant: A case report

Langerhans cell histiocytosis (LCH) is a proliferative disease of histiocyte-like cells, with a wide range of clinical presentations that vary from a solitary lesion to more severe multifocal or disseminated lesions. The disease can affect any age group; however, the peak incidence rate is in infants aged between 1 and 3 years-old. Diagnosis of LCH should be based on the synthetical analysis of clinical presentations, in addition to features of imaging and histopathology. Although certain cases regress spontaneously, other patients require systemic chemotherapy together with the administration of steroids. The present study reports the case of an infant with LDH with multisystem involvement, including that of the bone, skin, orbit, spleen and lungs. The patient received chemotherapy and obtained rapid improvement in the involved systems. A total of 2.5 years after completion of the therapy, the patient still remains in follow-up and no evidence of active disease has been noted.

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.

The genetics of interdigitating dendritic cell sarcoma share some changes with Langerhans cell histiocytosis in select cases

Histiocytic disorders have been noted to have evidence of transdifferentiation; examples of cases with combinations of different lineages have been shown. In our index case, we identified interdigitating dendritic cell (IDC) differentiation in a case of Langerhans cell histiocytosis (LCH). Little is currently known about the genetics of IDC sarcoma (IDCS) because they are exceedingly rare. Using array comparative genomic hybridization (aCGH), we evaluated 4 cases of IDCS and compared them with our index case, as well as genetic abnormalities previously found in LCH. Four cases of paraffin-embedded samples of IDCS and 1 case of LCH with IDC differentiation were evaluated using aCGH. Array CGH results showed no abnormalities in a case of LCH with interdigitating cell differentiation. In 3 of 4 cases of IDCS, genetic abnormalities were identified; 1 case had no identifiable abnormalities. Interdigitating dendritic cell sarcoma case 1 had gains of 3q and 13q; IDCS case 2 had trisomy 12; IDCS case 3 had deletions of 7p, 12p, 16p, 18q, 19q, and 22q; and IDCS case 4 had no detectable abnormalities. Our index case, LCH with IDC differentiation, showed no abnormalities by aCGH. A number of LCH cases do not have detectable genetic abnormalities. In contrast, 3 of 4 cases of IDCS evaluated had identifiable abnormalities by aCGH. Furthermore, 2 of these shared abnormalities, albeit of large genetic regions, with published abnormalities seen in LCH. No recurrent abnormalities were identified in the IDCS cases. However, the possibility of a relationship between IDCS and LCH cannot be entirely excluded by these results.

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.

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's cell histiocytosis in old subjects: two rare case reports and review of the literature

BACKGROUND

Langerhans cell histiocytosis (LCH) is a proliferative disease of histiocyte-like cells that generally affects children; LCH onset is rare in adults; immunohistochemistry is essential to obtain the correct diagnosis, and treatment protocols are controversial.

OBJECTIVE

To describe two new cases of adult onset oral LCH.

CASE REPORTS

Case 1: a 71-year-old woman, complaining of diffuse oral pain, presented with erythematous mucosal lesions; the panoramic radiograph and CT scan showed multiple mandible radiolucent areas. Immunohistochemical assay for S-100, CD1a and langerin test was essential in reaching the correct diagnosis. Case 2: a 77-year-old female patient presented with a non-painful, non-bleeding, slightly elevated erythematous palatal lesion of 6 months duration, together with a genital vulvar lesion of uncertain nature. The pathology confirmed the diagnosis of LCH. Many therapies (etoposid, radiotherapy) could induce only a clinical partial remission; Cladribine induced a complete recovery.

CONCLUSION

The first case was difficult to diagnose: the clinical presentation and course of the disease (LCH) in the elderly are multiple and unpredictable. An immunohistochemistry study is often essential to obtain the correct diagnosis. The second case required several therapeutic interventions: even though some cases regress spontaneously, others require systemic chemotherapy.

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.

Role of p16 in the pathogenesis of Langerhans cell histiocytosis

Background

It has been hypothesized that genetic alteration at the cellular level may have a significant effect on cellular mechanisms controlling the proliferation and apoptosis of Langerhans cells (LCs).

Methods

We examined whether p16 protein expression can be used to predict the outcome of Langerhans cell histiocytosis (LCH). Archival paraffin blocks from children diagnosed with LCH and followed at the Asan Medical Center and Chungnam National University Hospital between March 1998 and February 2008 were studied.

Results

Slides were stained with p16 antibody and evaluated semi-quantitatively using the following scale: negative, no staining; ±, weakly positive; 1+, staining similar to lymphocytes surrounding the LCs; 2+, stronger staining than lymphocytes; 3+, much stronger staining than lymphocytes. Negative and ± groups were assigned to a lower expression group (LEG) and the 1+, 2+, and 3+ groups were assigned to a higher expression group (HEG). The median age of the 51 patients (24 girls, 27 boys) was 49 (range, 0.6-178) months, and LCH was diagnosed based on CD1a positivity. p16 protein was expressed to varying degrees in all but one specimen. There was a greater tendency toward multisystem disease, risk organ involvement, and relapse in the HEG than in the LEG.

Conclusion

The p16 protein may have a significant effect on cellular mechanisms controlling the proliferation and apoptosis of LCs, and thus may influence the clinical outcome and prognosis of LCH.

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.

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.

In vivo transformation of mouse conventional CD8alpha+ dendritic cells leads to progressive multisystem histiocytosis

Division and proliferation of dendritic cells (DCs) have been proposed to contribute to homeostasis and to prolonged antigen presentation. Whether abnormal proliferation of dendritic cells causes Langerhans cell histiocytosis (LCH) is a highly debated topic. Transgenic expression of simian virus 40 (SV40) T antigens in mature DCs allowed their transformation in vivo while maintaining their phenotype, function, and maturation capacity. The transformed cells were differentiated splenic CD8 alpha-positive conventional dendritic cells with increased Langerin expression. Their selective transformation was correlated with higher steady-state cycling compared with CD8 alpha-negative DCs in wild-type and transgenic mice. Mice developed a DC disease involving the spleen, liver, bone marrow, thymus, and mesenteric lymph node. Surprisingly, lesions displayed key immunohistologic features of Langerhans cell histiocytosis, including expression of Langerin and absence of the abnormal mitoses observed in Langerhans cell sarcomas. Our results demonstrate that a transgenic mouse model with striking similarities to aggressive forms of multisystem histiocytosis, such as the Letterer-Siwe syndrome, can be obtained by transformation of conventional DCs. These findings suggest that conventional DCs may cause some human multisystem LCH. They can reveal shared molecular pathways for human histiocytosis between humans and mice.