Recurrent NRAS mutations in pulmonary Langerhans cell histiocytosis

Current State of Targeted Therapy in Adult Langerhans Cell Histiocytosis and Erdheim-Chester Disease

The mitogen-activated protein kinase (MAPK) pathway is a key driver in many histiocytic disorders, including Langerhans cell histiocytosis (LCH) and Erdheim-Chester disease (ECD). This has led to successful and promising treatment with targeted therapies, including BRAF inhibitors and MEK inhibitors. Additional novel inhibitors have also demonstrated encouraging results. Nevertheless, there are several problems concerning targeted therapy that need to be addressed. These include, among others, incomplete responsiveness and the emergence of resistance to BRAF inhibition as observed in other BRAF-mutant malignancies. Drug resistance and relapse after treatment interruption remain problems with current targeted therapies. Targeted therapy does not seem to eradicate the mutated clone, leading to inevitable relapes, which is a huge challenge for the future. More fundamental research and clinical trials are needed to address these issues and to develop improved targeted therapies that can overcome resistance and achieve long-lasting remissions.

Diffuse Cystic Lung Disease: A Clinical Guide to Recognition and Management

TOPIC IMPORTANCE

Diffuse cystic lung diseases (DCLDs) represent a group of pathophysiologically heterogeneous entities that share a common radiologic phenotype of multiple thin-walled pulmonary cysts. DCLDs differ from the typical fibroinflammatory interstitial lung diseases in their epidemiology, clinical presentation, molecular pathogenesis, and therapeutic approaches, making them worthy of a distinct classification. The importance of timely and accurate identification of DCLDs is heightened by the impact on patient management including recent discoveries of targeted therapeutic approaches for some disorders.

REVIEW FINDINGS

This article offers a practical framework for evaluating patients with DCLD, indicating the most appropriate and current diagnostic and management approaches. We focus on the DCLDs that are most likely to be encountered by practicing pulmonologists: lymphangioleiomyomatosis, pulmonary Langerhans cell histiocytosis, Birt-Hogg-Dubé syndrome, and lymphoid interstitial pneumonia. Chest CT scan is the most informative noninvasive diagnostic modality to identify DCLDs. Thereafter, instituting a structured approach to high-yield associated factors (eg, medical, social, and family history; renal and dermatologic findings) increases the likelihood of identifying DCLDs and achieving a diagnosis.

SUMMARY

Although the individual diseases that comprise the DCLD family are rare, taken together, DCLDs can be encountered more frequently in clinical practice than commonly perceived. An increased eagerness among general pulmonary physicians to recognize these entities, coupled with a practical and systematic clinical approach to examinations and investigations, is required to improve case findings, allow earlier intervention, and reduce morbidity and mortality.

Treatment of Langerhans Cell Histiocytosis and Histiocytic Disorders: A Focus on MAPK Pathway Inhibitors

Histiocytic disorders are rare diseases defined by the clonal accumulation of a macrophage or dendritic cell origin. These disorders include Langerhans cell histiocytosis, Erdheim-Chester disease, juvenile xanthogranuloma, malignant histiocytoses, and Rosai-Dorfman-Destombes disease. These histiocytic disorders are a diverse group of disorders with different presentations, management, and prognosis. This review focuses on these histiocytic disorders and the role of pathological ERK signaling due to somatic mutations in the mitogen--activated protein kinase (MAPK) pathway. Over the last decade, there has been growing awareness of the MAPK pathway being a key driver in many histiocytic disorders, which has led to successful treatment with targeted therapies, in particular, BRAF inhibitors and MEK inhibitors.

The world of rare interstitial lung diseases

The world of rare interstitial lung diseases (ILDs) is diverse and complex. Diagnosis and therapy usually pose challenges. This review describes a selection of rare and ultrarare ILDs including pulmonary alveolar proteinosis, pulmonary alveolar microlithiasis and pleuroparenchymal fibroelastosis. In addition, monogenic ILDs or ILDs in congenital syndromes and various multiple cystic lung diseases will be discussed. All these conditions are part of the scope of the European Reference Network on rare respiratory diseases (ERN-LUNG). Epidemiology, pathogenesis, diagnostics and treatment of each disease are presented.

Signaling pathways, microenvironment, and targeted treatments in Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is an inflammatory myeloid malignancy in the "L-group" histiocytosis. Mitogen-activated protein kinase (MAPK) pathway activating mutations are detectable in nearly all LCH lesions. However, the pathogenic roles of MAPK pathway activation in the development of histiocytosis are still elusive. This review will summarize research concerning the landscape and pathogenic roles of MAPK pathway mutations and related treatment opportunities in Langerhans cell histiocytosis. Video abstract.

Langerhans Cell Histiocytosis-Associated Pulmonary Adenocarcinoma: A Word of Caution during Molecular Determinations

Background: Smoking habit is a common cause of pulmonary Langerhans cell histiocytosis (PLCH) and lung cancer and both diseases may coexist in the lung and share genetic alterations, such as V600E BRAF mutations. We collected a small series of three cases of PLCH-associated lung adenocarcinoma in order to evaluate the molecular setup in both components and underline the critical role of careful tissue selection for predictive molecular driver testing. Methods: Three cases of PLCH-associated adenocarcinoma were collected from consultation files. Clinical data from referring physicians and clinical data were obtained. The surgical biopsies were tested by immunohistochemistry and molecular analysis after separate dissection of adenocarcinoma cells and Langerhans histiocytes. Results: There were three active smoking men with a median age at diagnosis of 60.6 years. PLCH was disclosed at imaging during work-up for suspected lung cancer. Molecular analysis revealed KRAS (G12C and G13C) mutations in two cases and V600E BRAF mutation in one case of PLCH. Immunostaining with the V600E BRAF mutation specific primary antibody VE1 correctly recognized BRAF-mutated LCH. One case was wild-type in both diseases. Two similar cases were found in the literature, one of which showed a discrepant KRAS (G12D) mutation in adenocarcinoma and a V600E BRAF mutation in LCH; Conclusions: This case series of PLCH-associated adenocarcinoma underline the possibility to disclose identical genetic alterations in co-existing benign and malignant pathologies, then potentially creating erroneous interpretation of molecular analysis leading to inadequate therapeutic options in case of incorrect diagnostic recognition and inappropriate selection of both components through microdissection.

Case report: Common clonal origin of concurrent langerhans cell histiocytosis and acute myeloid leukemia

Langerhans cell histiocytosis (LCH) and acute myeloid leukemia (AML) are distinct entities of blood neoplasms, and the exact developmental origin of both neoplasms are considered be heterogenous among patients. However, reports of concurrent LCH and AML are rare. Herein we report a novel case of concurrent LCH and AML which shared same the driver mutations, strongly suggesting a common clonal origin.An 84-year-old female presented with cervical lymphadenopathy and pruritic skin rash on the face and scalp. Laboratory tests revealed pancytopenia with 13% of blasts, elevated LDH and liver enzymes, in addition to generalised lymphadenopathy and splenomegaly by computed tomography. Bone marrow specimens showed massive infiltration of MPO-positive myeloblasts, whereas S-100 and CD1a positive atypical dendritic cell-like cells accounted for 10% of the atypical cells on bone marrow pathology, suggesting a mixture of LCH and AML. A biopsy specimen from a cervical lymph node and the skin demonstrated the accumulation of atypical cells which were positive for S-100 and CD1a. LCH was found in lymph nodes, skin and bone marrow; AML was found in peripheral blood and bone marrow (AML was predominant compared with LCH in the bone marrow).

Next generation sequencing revealed four somatic driver mutations (NRAS-G13D, IDH2-R140Q, and DNMT3A-F640fs/-I715fs), equally shared by both the lymph node and bone marrow, suggesting a common clonal origin for the concurrent LCH and AML. Prednisolone and vinblastine were initially given with partial response in LCH; peripheral blood blasts also disappeared for 3 months. Salvage chemotherapy with low dose cytarabine and aclarubicin were given for relapse, with partial response in both LCH and AML. She died from pneumonia and septicemia on day 384. Our case demonstrates a common cell of origin for LCH and AML with a common genetic mutation, providing evidence to support the proposal to classify histiocytosis, including LCH, as a myeloid/myeloproliferative malignancy.

Langerin-expressing dendritic cells in pulmonary immune-related diseases

Dendritic cells (DCs) are “frontline” immune cells dedicated to antigen presentation. They serve as an important bridge connecting innate and adaptive immunity, and express various receptors for antigen capture. DCs are divided into various subclasses according to their differential expression of cell surface receptors and different subclasses of DCs exhibit specific immunological characteristics. Exploring the common features of each sub-category has became the focus of many studies. There are certain amounts of DCs expressing langerin in airways and peripheral lungs while the precise mechanism by which langerin⁺ DCs drive pulmonary disease is unclear. Langerin-expressing DCs can be further subdivided into numerous subtypes based on the co-expressed receptors, but here, we identify commonalities across these subtypes that point to the major role of langerin. Better understanding is required to clarify key disease pathways and determine potential new therapeutic approaches.

Prevalence of the BRAF V600E mutation in Greek adults with Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is a rare inflammatory myeloid neoplasia with a broad spectrum of clinical manifestations. The activation of the MAP kinase pathway plays an integral role in its pathogenesis with genetic alterations found in the majority of cases that most frequently involve a somatic mutation of the oncogenic BRAF^V600E variant. In this study we investigated the prevalence of the BRAF^V600E mutation and its clinical relevance in adult Greek patients with LCH. Among 37 patients studied, the BRAF^V600E mutation was identified in 12 out of 31 (38.7%), whereas in six patients (19.3%) the results were in conclusive. The presence of the mutation did not correlate with age at diagnosis, organ involvement, disease extent, response to initial treatment, development of diabetes insipidus and relapse risk. In our series the prevalence of the BRAF^V600E mutation is at the lower range of the relative percentage found in children, but in line to that obtained in previous studies of adult patients with LCH that have found an up to 50% prevalence of the BRAF^V600E mutation in these patients. Further studies with a larger number of adults are needed to identify the exact prevalence of mutations in the RAS-RAF-MEK-ERK pathway and their role on clinical parameters and disease outcomes.Supplemental data for this article is available online at https://doi.org/10.1080/08880018.2022.2029988 .

Two smoking-related lesions in the same pulmonary lobe of squamous cell carcinoma and pulmonary Langerhans cell histiocytosis: A case report

BACKGROUND

Pulmonary Langerhans cell histiocytosis (PLCH) is a rare cystic lung disease usually affecting young adults. It is predicted that PLCH is a lung tumor precursor associated with dysfunction of the myeloid dendritic cells in the lung.

CASE SUMMARY

A 70-year-old male patient presented with chronic cough and sputum. He had symptoms for 5 years and described shortness of breath on exertion for the previous 3 years. He had a 60 packs/year smoking history. Computerized tomography of the thorax revealed an 11-mm nodule in the right lung lower lobe superior segment and a 7-mm nodule in the right lung lower lobe poster basal segment. Those two nodules were resected by means of right thoracoscopic surgery. Pathological evaluation revealed a squamous cell carcinoma and PLCH.

CONCLUSION

Coexistent squamous cell carcinoma and PLCH suggest possible association between PLCH and lung cancer.

Recurrence of primary disease following lung transplantation

Lung transplant has become definitive treatment for patients with several end-stage lung diseases. Since the first attempted lung transplantation in 1963, survival has significantly improved due to advancement in immunosuppression, organ procurement, ex vivo lung perfusion, surgical techniques, prevention of chronic lung allograft dysfunction and bridging to transplant using extracorporeal membrane oxygenation. Despite a steady increase in number of lung transplantations each year, there is still a huge gap between demand and supply of organs available, and work continues to select recipients with potential for best outcomes. According to review of the literature, there are some rare primary diseases that may recur following transplantation. As the number of lung transplants increase, we continue to identify disease processes at highest risk for recurrence, thus shaping our future approaches. While the aim of lung transplantation is improving survival and quality of life, choosing the best recipients is crucial due to a shortage of donated organs. Here we discuss the common disease processes that recur and highlight its impact on overall outcome following lung transplantation.

This article reviews the underlying conditions leading to lung transplant with potential for recurrence and the impact of such recurrences on the overall outcome following transplanthttps://bit.ly/3v3gSvJ

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

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

Pulmonary Langerhans cell histiocystosis (PLCH) and lymphangioleiomyomatosis (LAM) have circulating cells with loss of heterozygosity of the TSC2 gene

BACKGROUND

Lymphangioleiomyomatosis (LAM) and pulmonary Langerhans Cell Histiocytosis (PLCH) are cystic lung diseases in which a neoplastic cell is believed to be responsible for disease pathogenesis. The neoplastic LAM cell has mutations in the Tuberous Sclerosis Complex (TSC) genes, TSC1 or TSC2, whereas the neoplastic PLCH cell may have mutations in several genes, e.g., BRAF, NRAS, MAP2K1. These mutations are not specific for PLCH and they have been described in multiple cancers. TSC1 or TSC2 mutations and loss of heterozygosity (LOH) have also been described in cancers.

RESEARCH QUESTION

Is TSC2 LOH specific to LAM or is it also found in PLCH too?

STUDY DESIGN

We recruited LAM patients (53) and Healthy Volunteers (22) and compared the presence of cells with TSC2 LOH with PLCH patients (12). Blood and urine samples were collected for analysis.

METHODS

Fluorescence-activated cell sorting (FACS) was used to identify subpopulations of cells from blood and urine samples. We isolated CD45-CD235a-, CD45-CD235a+, CD45+CD235a- cells from blood following density gradient separation. Cells were screened for TSC2 LOH at 5 microsatellites markers (i.e., kg8, D16S3395, D16S3024, D16S521, D16S291). We obtained four cell subpopulations from urine (i.e., CD44v6+CD9+; CD44v6+CD9-; CD44v6-CD9+; CD44v6-CD9).

RESULTS

Using FACS, cells were isolated from blood and urine from PLCH patients that showed TSC2 LOH. Healthy volunteers did not have cells with TSC2 LOH. As a control, cells isolated from blood and urine from LAM patients gave results similar to those reported previously. These data show that TSC2 LOH is found in patients with cystic lung diseases with potential neoplastic characteristics, as well as in patients with cancer.

INTERPRETATION

The presence of TSC2 LOH in circulating cells is not specific for LAM. The data suggest that chromosomal abnormalities affecting the TSC2 gene are found in other diseases associated with cells having cancer-like neoplastic cells.

Histiocytic disorders

The historic term 'histiocytosis' meaning 'tissue cell' is used as a unifying concept for diseases characterized by pathogenic myeloid cells that share histological features with macrophages or dendritic cells. These cells may arise from the embryonic yolk sac, fetal liver or postnatal bone marrow. Prior classification schemes align disease designation with terminal phenotype: for example, Langerhans cell histiocytosis (LCH) shares CD207+ antigen with physiological epidermal Langerhans cells. LCH, Erdheim-Chester disease (ECD), juvenile xanthogranuloma (JXG) and Rosai-Dorfman disease (RDD) are all characterized by pathological ERK activation driven by activating somatic mutations in MAPK pathway genes. The title of this Primer (Histiocytic disorders) was chosen to differentiate the above diseases from Langerhans cell sarcoma and malignant histiocytosis, which are hyperproliferative lesions typical of cancer. By comparison LCH, ECD, RDD and JXG share some features of malignant cells including activating MAPK pathway mutations, but are not hyperproliferative. 'Inflammatory myeloproliferative neoplasm' may be a more precise nomenclature. By contrast, haemophagocytic lymphohistiocytosis is associated with macrophage activation and extreme inflammation, and represents a syndrome of immune dysregulation. These diseases affect children and adults in varying proportions depending on which of the entities is involved.

Mitogen-activating protein kinase pathway alterations in Langerhans cell histiocytosis

PURPOSE OF REVIEW

Langerhans cell histiocytosis (LCH) is a rare disorder characterized by the infiltration of involved tissues by specialized dendritic cells. The demonstration of the constant activation of the mitogen-activated protein kinase (MAPK) pathway in LCH lesions has been a breakthrough in the understanding of the pathogenesis of this rare disease. We will summarize the current knowledge on MAPK alterations in LCH and the new therapeutic options indicated by these findings.

RECENT FINDINGS

Since the description of the B-Raf proto-oncogene, serine/threonine kinase (BRAF)V600E mutation in LCH lesions, several other molecular alterations affecting the MAPK pathway have been identified in most cases. Based on these driver alterations, LCH cells were shown to be derived from hematopoietic precursors, which yielded the current concept of LCH as a myeloid inflammatory neoplasia. MAPK pathway inhibitors have emerged as an innovative therapy in severe forms of LCH, resulting in virtually no acquired resistance. However, although they are highly effective, their effect is only temporary, as the disease relapses upon discontinuation of the treatment.

SUMMARY

LCH is an inflammatory myeloid neoplastic disorder, driven by mutations activating the MAPK pathway. MAPK-targeted treatments represent an important stepforward in the management of patients with severe progressive LCH.

Pulmonary granulomatosis of genetic origin

Granulomatous inflammation of the lung can be a manifestation of different conditions and can be caused by endogenous inflammation or external triggers. A multitude of different genetic mutations can either predispose patients to infections with granuloma-forming pathogens or cause autoinflammatory disorders, both leading to the phenotype of pulmonary granulomatosis. Based on a detailed patient history, physical examination and a diagnostic approach including laboratory workup, pulmonary function tests (PFTs), computed tomography (CT) scans, bronchoscopy with bronchoalveolar lavage (BAL), lung biopsies and specialised microbiological and immunological diagnostics, a correct diagnosis of an underlying cause of pulmonary granulomatosis of genetic origin can be made and appropriate therapy can be initiated. Depending on the underlying disorder, treatment approaches can include antimicrobial therapy, immunosuppression and even haematopoietic stem cell transplantation (HSCT). Patients with immunodeficiencies and autoinflammatory conditions are at the highest risk of developing pulmonary granulomatosis of genetic origin. Here we provide a review on these disorders and discuss pathogenesis, clinical presentation, diagnostic approach and treatment.

Pulmonary granulomatosis of genetic origin mostly occurs in immunodeficiency disorders and autoinflammatory conditions. In addition to specific approaches in this regard, the diagnostic workup needs to cover environmental and occupational aspects.https://bit.ly/31SqdHW

[Cystic lung diseases]

Cystic lung diseases present uncommonly and have an undetermined incidence. Cysts result from a broad spectrum of causative mechanisms and diseases leading to variable clinical presentations. The pathogenic mechanisms that can lead to lung cyst formation include infection, neoplastic, systemic, traumatic, genetic and congenital processes. A rigorous, systemic and multidisciplinary approach is advised in the diagnostic workup of these conditions. In this article, we review cystic lung diseases including their presentation and management.

Update on Pulmonary Langerhans Cell Histiocytosis

Pulmonary Langerhans cell (LC) histiocytosis (PLCH) has unknown cause and is a rare neoplastic disorder characterized by the infiltration of lungs and various organs by bone marrow-derived Langerhans cells with an accompanying strong inflammatory response. These cells carry somatic mutations of BRAF gene and/or NRAS, KRAS, and MAP2K1 genes, which cause activation of the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) signaling pathway. PLCH occurs predominantly in young smokers, without gender predominance. Lungs might be involved as an isolated organ or as part of a multiorgan disease. High-resolution computed chest tomography plays an outstanding role in PLCH diagnosis. The typical radiological picture of PLCH is the presence of small intralobular nodules, “tree in bud” opacities, cavitated nodules, and thin- and thick-walled cysts, frequently confluent. Histological examination of the lesion and demonstration of characteristic eosinophilic granulomas with the presence of LCs that display antigen CD1a or CD207 in immunohistochemistry are required for definite diagnosis. Smoking cessation is the most important recommendation for PLCH patients, but treatment of progressive PLCH and multisystem disease is based on chemotherapy. Recently, new targeted therapies have been implemented.

Initial presentation of Pulmonary Langerhans cell histiocytosis as recurrent spontaneous pneumothoraces

Pulmonary Langerhans cell histiocytosis (PLCH) is a rare cystic lung disease. The natural history is often unpredictable making it difficult to diagnose. We report a 63-year-old male with dyspnoea, chronic cough and recurrent respiratory tract infections, who developed progressive multifocal cystic lesions on pulmonary nodule surveillance over 4 years. He was a heavy smoker with a history of multiple spontaneous pneumothoraces in his teens. Extensive investigations culminated in a thoracoscopic wedge resection, which identified histiocytic nodules staining positive for CD1a and thus confirming the diagnosis of PLCH. It is now apparent that PLCH was the likely cause of his pneumothoraces.

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PLCH is difficult to diagnose due to its heterogeneous presentation and insidious natural history.

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PLCH is a cause of recurrent pneumothoraces, and almost exclusively in smokers.

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PLCH usually has innumerable cystic lesions that progress in a nodulocystic pattern.

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CD1 antigen is characteristic of PLCH as it is uniquely expressed in Langerhans-like dendritic cells.

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Smoking cessation is an effective first line monotherapy for PLCH.

A Melanoma-Tailored Next-Generation Sequencing Panel Coupled with a Comprehensive Analysis to Improve Routine Melanoma Genotyping

BACKGROUND

Tumor molecular deciphering is crucial in clinical management. Pan-cancer next-generation sequencing panels have moved towards exhaustive molecular characterization. However, because of treatment resistance and the growing emergence of pharmacological targets, tumor-specific customized panels are needed to guide therapeutic strategies.

OBJECTIVE

The objective of this study was to present such a customized next-generation sequencing panel in melanoma.

METHODS

Melanoma patients with somatic molecular profiling performed as part of routine care were included. High-throughput sequencing was performed with a melanoma tailored next-generation sequencing panel of 64 genes involved in molecular classification, prognosis, theranostic, and therapeutic resistance. Single nucleotide variants and copy number variations were screened, and a comprehensive molecular analysis identified clinically relevant alterations.

RESULTS

Four hundred and twenty-one melanoma cases were analyzed (before any treatment initiation for 94.8% of patients). After bioinformatic prioritization, we uncovered 561 single nucleotide variants, 164 copy number variations, and four splice-site mutations. At least one alteration was detected in 368 (87.4%) lesions, with BRAF, NRAS, CDKN2A, CCND1, and MET as the most frequently altered genes. Among patients with BRAFV600 mutated melanoma, 44.5% (77 of 173) harbored at least one concurrent alteration driving potential resistance to mitogen-activated protein kinase inhibitors. In patients with RAS hotspot mutated lesions and in patients with neither BRAFV600 nor RAS hotspot mutations, alterations constituting potential pharmacological targets were found in 56.9% (66 of 116) and 47.7% (63 of 132) of cases, respectively.

CONCLUSIONS

Our tailored next-generation sequencing assay coupled with a comprehensive analysis may improve therapeutic management in a significant number of patients with melanoma. Updating such a panel and implementing multi-omic approaches will further enhance patients' clinical management.

Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is caused by clonal expansion of myeloid precursors that differentiate into CD1a+/CD207+ cells in lesions that leads to a spectrum of organ involvement and dysfunction. The pathogenic cells are defined by constitutive activation of the MAPK signaling pathway. Treatment of LCH is risk-adapted: patients with single lesions may respond well to local treatment, whereas patients with multisystem disease require systemic therapy. Although survival rates for patients without organ dysfunction is excellent, mortality rates for patients with organ dysfunction may reach 20%. Despite progress made in the treatment of LCH, disease reactivation rates remain above 30%, and standard second-line treatment is yet to be established. Treatment failure is associated with increased risks for death and long-term morbidity, including LCH-associated neurodegeneration. Early case series report promising clinical responses in patients with relapsed and refractory LCH treated with BRAF or MEK inhibitors, although potential for this strategy to achieve cure remains uncertain.

Multisystem involvement Langerhans cell histiocytosis in an adult: A case report

BACKGROUND

Langerhans cell histiocytosis (LCH) is a rare condition wherein Langerhans cells proliferate abnormally, adversely impacting organs including lymph nodes, bones, skin, lungs, and pituitary gland. The LCH disease course varies widely among patients from a self-limiting condition to one that progresses rapidly and culminates in death. It is uncommon for multisystem LCH to be observed in adults. Herein we describe a woman suffering from multi-system LCH involvement.

CASE SUMMARY

A 37-year old Chinese woman was admitted to the hospital in June 2019 suffering from dyspnea that had progressed over the course of 5 years. Her medical history included: central diabetes insipidus (DI) that had been treated via radiotherapy, desmopressin acetate, and bromocriptine; bilateral pneumothorax with two surgeries having been performed to remove bullae; and autoimmune hepatitis that had been unsuccessfully treated using a combination of methylprednisolone and mycophenolate mofetil. A chest computed tomography (CT) scan revealed the presence of multiple pulmonary cysts of varying sizes. We re-analyzed right pulmonary bullae samples that had been removed in 2014, performed a systematic ¹⁸F-FDG PET/CT analysis, and convened a multidisciplinary medical team to diagnose and treat this patient. As a result, we were able to eventually diagnose this patient with LCH that was not associated with BRAF-V600E mutations.

CONCLUSION

We hope to emphasize the importance of systemic evaluation and of cooperation between multidisciplinary physicians with the goal of improving awareness and detection of this orphan disease.

Ultra-rare cystic disease

Diffuse cystic lung diseases include a group of heterogeneous disorders characterised by the presence of cysts within the lung parenchyma, sometimes showing a characteristic computed tomography scan pattern that allows diagnosis. The pathogenetic mechanisms underlying cyst formation in the lung are still not clear and a number of hypotheses have been postulated according to the different aetiologies: ball-valve effect, ischaemic dilatation of small airways and alveoli related to infiltration and obstruction of small vessels and capillaries that supply the terminal bronchioles and connective tissue degradation by matrix metalloproteases. A wide number of lung cyst diseases have been classified into six diagnostic groups according to the aetiology: neoplastic, congenital/genetic, lymphoproliferative, infective, associated with interstitial lung diseases, and other causes. This article focuses on lymphangioleiomyomatosis, pulmonary Langerhans cell histiocytosis and Erdheim–Chester disease, Birt–Hogg–Dubé, follicular bronchiolitis and lymphocytic interstitial pneumonia, light-chain deposition disease and amyloidosis, congenital lung disease associated with aberrant lung development and growth, and cystic lung disease associated with neoplastic lesion. These cystic diseases are epidemiologically considered as ultra-rare conditions as they affect fewer than one individual per 50 000 or fewer than 20 individuals per million. Despite the rarity of this group of disorders, the increasing use of high-resolution computed tomography has improved the diagnostic yield, even in asymptomatic patients allowing prompt and correct therapy and management without the need for a biopsy.

Diffuse cystic lung diseases show a characteristic CT scan pattern that often allows for diagnosis, even in asymptomatic patients, allowing prompt correct therapy and management without the needing of a biopsyhttps://bit.ly/2wIUKet

Custom pyrosequencing assay to detect short BRAF deletions in Langerhans cell histiocytic lesions

Langerhans cell histiocytosis (LCH) is a rare inflammatory myeloid neoplastic disease driven by activating mutations in the mitogen-activating protein kinase signalling pathway, including the BRAF ^V600E mutation and BRAF deletions (BRAFdel). Next-generation sequencing and whole exome sequencing (WES) are valuable and powerful approaches for BRAFdel identification, but these techniques are costly and time consuming. Pyrosequencing is an alternative method that has the potential to rapidly and reliably identify gene deletions. We developed a custom pyrosequencing assay to detect the exon-12 BRAFdel in 18 biopsies from adult patients with LCH, which were all genotyped in parallel using Sanger sequencing and WES. A BRAFdel was detected in 7/18 (39%), 6/18 (33%) and 3/18 (17%) LCH lesions using WES, pyrosequencing and Sanger, respectively, with good concordance between the WES and pyrosequencing results (Kappa-coefficient=0.88). Therefore, our pyrosequencing assay is reliable and useful for detecting BRAFdel, particularly in BRAF ^V600E-negative LCH lesions, for which targeted treatment is indicated.

Management of severe pulmonary Langerhans cell histiocytosis in children

Patients with pulmonary Langerhans cell histiocytosis (LCH) typically have a benign course but may have extensive cystic lung disease with rare life-threatening complications including multiple and recurrent pneumothoraces and respiratory failure. We report seven severely affected pediatric patients treated with chemotherapy, aggressive chest tube management, and pleurodesis of whom five survived. Patients with extraordinary amounts of pulmonary cystic disease and multiple pneumothoraces due to LCH can have remarkable, curative outcomes with early recognition, optimal LCH-directed therapy, and supportive care.

Lack of evidence for the involvement of Merkel cell polyomavirus in pulmonary Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is currently considered a rare neoplastic disease with an inflammatory component, driven by genomic alterations in the mitogen-activating protein kinase (MAPK) pathway, including BRAF^V600E, MAP2K1 mutations and BRAF deletions [1, 2]. Lung involvement is frequently observed in adult LCH patients, almost exclusively in young smokers of both sexes [3]. The aetiology of LCH, including pulmonary LCH (PLCH), remains unknown. A viral triggering factor of LCH has long been suspected, but the results of studies are inconclusive [4, 5].

Compared to control lung tissues from smokers, MCPyV DNA is rarely detected in PLCH lesions and is not associated with alterations of the MAPK pathway. A viral trigger in PLCH pathogenesis remains elusive.https://bit.ly/2xKmkIo

Genetic landscape of adult Langerhans cell histiocytosis with lung involvement

The clinical significance of the BRAF ^V600E mutation in adult Langerhans cell histiocytosis (LCH), including pulmonary Langerhans cell histiocytosis (PLCH), is not well understood. Similarly, the spectrum of molecular alterations involved in adult LCH has not been fully delineated. To address these issues, we genotyped a large number of adult LCH biopsies and searched for an association of identified molecular alterations with clinical presentation and disease outcome.Biopsies from 117 adult LCH patients, 83 with PLCH (median age 36.4 years, 56 females, 38 multisystem disease, 79 single system disease, 65 current smokers) were genotyped for the BRAF ^V600E mutation. In 69 cases, LCH lesions were also genotyped by whole-exome sequencing (WES) or targeted gene panel next-generation sequencing (NGS). Cox models were used to estimate the association of baseline characteristics with the hazard of LCH progression.MAPK pathway alterations were detected in 59 out of 69 cases (86%) (BRAF ^V600E mutation: 36%, BRAF ^N486_P490 deletion: 28%, MAP2K1 mutations: 15%, isolated NRAS ^Q61 mutations: 4%), while KRAS mutations were virtually absent in PLCH lesions. The BRAF ^V600E mutation was not associated with LCH presentation at diagnosis, including smoking status and lung function, in PLCH patients. BRAF ^V600E status did not influence the risk of LCH progression over time.Thus, MAPK alterations are present in most lesions from adult LCH patients, particularly in PLCH. Unlike reports in paediatric LCH, BRAF ^V600E genotyping did not provide additional information on disease outcome. The search for alterations involved in the MAPK pathway, including BRAF deletions, is useful for guiding targeted treatment in selected patients with refractory progressive LCH.

Management and outcomes of pneumothorax in adult patients with Langerhans cell Histiocytosis

BACKGROUND

Pneumothorax may recur during pulmonary Langerhans cell histiocytosis (PLCH) patients' follow-up and its management is not standardised. The factors associated with pneumothorax recurrence are unknown.

METHODS

In this retrospective study, PLCH patients who experienced a pneumothorax and were followed for at least 6 months after the first episode were eligible. The objectives were to describe the treatment of the initial episode and pneumothorax recurrences during follow-up. We also searched for factors associated with pneumothorax recurrence and evaluated the effect on lung function outcome. Time to recurrence was estimated by the Kaplan Meier method and the cumulative hazard of recurrence handling all recurrent events was estimated. Univariate Cox models and Andersen-Gill counting process were used for statistical analyses.

RESULTS

Fourty-three patients (median age 26.5 years [interquartile range (IQR), 22.9-35.4]; 26 men, 39 current smokers) were included and followed for median time of 49 months. Chest tube drainage was the main management of the initial pneumothorax, which resolved in 70% of cases. Pneumothorax recurred in 23 (53%) patients, and overall 96 pneumothoraces were observed during the study period. In the subgroup of patients who experienced pneumothorax recurrence, the median number of episodes per patient was 3 [IQR, 2-4]. All but one recurrence occurred within 2 years after the first episode. Thoracic surgery neither delayed the time of occurrence of the first ipsilateral recurrence nor reduced the overall number of recurrences during the study period, although the rate of recurrence was lower after thoracotomy than following video-assisted thoracic surgery (p = 0.03). At the time of the first pneumothorax, the presence of air trapping on lung function testing was associated with increased risk of recurrence (hazard ratio = 5.08; 95% confidence interval [1.18, 21.8]; p = 0.03). Pneumothorax recurrence did not predict subsequent lung function decline (p = 0.058).

CONCLUSIONS

Our results show that pneumothorax recurrences occur during an "active" phase of PLCH. In this observational study, the time of occurrence of the first ipsilateral recurrence and the overall number of pneumothorax recurrences were similar after conservative and thoracic surgical treatments. Further studies are needed to determine the best management to reduce the risk of pneumothorax recurrence in PLCH patients.

Detection of NRAS mutation in cell-free DNA biological fluids from patients with kaposiform lymphangiomatosis

Background

Kaposiform lymphangiomatosis (KLA) has recently been distinguished as a novel subtype of generalized lymphatic anomaly (GLA) with foci of spindle endothelial cells. All cases of KLA involve multiple organs and have an unfavorable prognosis. However, the molecular pathogenesis is unknown, and there are no useful biomarkers. In the present study, we performed genetic analysis to elucidate the cause of this disease and detect biomarkers for it.

Methods

We performed whole-exome sequencing of DNA samples from leukocytes and a biopsy specimen and analyzed cell-free DNA (cfDNA) from plasma and pleural effusion of patients to identify the NRAS c.182A > G (p.Q61R) mutation using the droplet digital polymerase chain reaction (ddPCR).

Results

All KLA patients (patients 1–5) had invasive and aggressive features (hemorrhagic pleural effusions, coagulation disorder, and thrombocytopenia) and characteristic findings of KLA in their pathological examinations. In whole exome sequencing for patient 1, c.182A > G missense variant (p.Q61R) in NRAS was identified in fresh frozen samples of a mass on the left chest wall at a frequency of 5% of total alleles but not in his blood leukocytes. Furthermore, the same mutation was detected in cfDNA isolated from plasma and pleural effusion by using ddPCR. ddPCR analysis of plasma/pleural effusion samples from an additional four KLA patients showed that the same mutation was detected in isolated cfDNA in three of the four, as well as in a tissue sample from one of the three plasma/effusion-positive patients that had been obtained to confirm the mutation.

Conclusion

These results provide the first evidence that NRAS oncogenic variant was identified in DNA samples from KLA patients from not only two affected lesions but also plasma and pleural effusion.

Association between clinicopathologic characteristics and BRAFV600E expression in Chinese patients with Langerhans cell histiocytosis

Background

The identification of V‐raf murine sarcoma viral oncogene homolog B1 (BRAF)^V600E mutations has been recommended in patients with Langerhans cell histiocytosis (LCH) with difficult diagnosis and failure of first‐line treatment. The reported frequencies of BRAF^V600E mutations vary in Chinese patients with LCH.

Methods

We conducted a retrospective analysis of LCH patients with a definitive pathological diagnosis who were hospitalized between 2013 and 2017. The BRAF^V600E mutations were detected with the human BRAF^V600E amplification refractory mutation system‐PCR (ARMS‐PCR) kit from the collected tissue samples.

Results

This study consisted of 46 male (68.7%) and 21 female (31.3%) patients, with a mean age of 29.1 years (range, 2–76 years). Most were adults (45/67.2%) with the multisysytem‐LCH (MS‐LCH) disease subtype (49/61.3%). The overall frequency of BRAF^V600E mutations was 22.4% (15 of 67 patients), confirmed by PCR analysis. These mutations were not closely correlated with age (nonadults vs. adults = 5/22.7% vs. 10/22.2%, P = 0.54), gender (female vs. male = 9/19.6% vs. 6/28.6%, P = 0.61), LCH classification type (single system: MS‐risk organ⁺: MS‐risk organ⁻ = 3/16.7%: 12:28.6%: 0, P = 0.19) or prognosis (cured: improved/stable: exacerbated: died = 4/44.4%: 19.2%: 20%: 0, P = 0.37). There were 33 patients (49.2%) with lung involvement, and 12 patients (36.3%) underwent lung biopsies; after screening, four patients were diagnosed with solitary pulmonary LCH, all of whom were negative for BRAF^V600E mutations.

Conclusion

The BRAF^V600E mutation rate in patients with LCH was lower than those reported in other studies. In addition, BRAF^V600E mutations might not be correlated with age, gender, LCH classification type or prognosis for Chinese cases.

A targeted genomic alteration analysis predicts survival of melanoma patients under BRAF inhibitors

Several mechanisms have been described to elucidate the emergence of resistance to MAPK inhibitors in melanoma and there is a crucial need for biomarkers to identify patients who are likely to achieve a better and long-lasting response to BRAF inhibitors therapy. In this study, we developed a targeted approach combining both mRNA and DNA alterations analysis focusing on relevant gene alterations involved in acquired BRAF inhibitor resistance. We collected baseline tumor samples from 64 melanoma patients at BRAF inhibitor treatment initiation and showed that the presence, prior to treatment, of mRNA over-expression of genes' subset was significantly associated with improved progression free survival and overall survival. The presence of DNA alterations was in favor of better overall survival. The genomic analysis of relapsed-matched tumor samples from 20 patients allowed us to uncover the largest landscape of resistance mechanisms reported to date as at least one resistance mechanism was identified for each patient studied. Alterations in RB1 have been most frequent and hence represent an important additional acquired resistance mechanism. Our targeted genomic analysis emerges as a relevant tool in clinical practice to identify those patients who are more likely to achieve durable response to targeted therapies and to exhaustively describe the spectrum of resistance mechanisms. Our approach can be adapted to new targeted therapies by including newly identified genetic alterations.

KRAS mutation in secondary malignant histiocytosis arising from low grade follicular lymphoma

Background

Transformation of follicular lymphoma most typically occurs as diffuse large B-cell lymphoma, however other forms of transformation such as classic Hodgkin lymphoma and lymphoblastic transformation can occur. Secondary malignant histiocytosis also represents a rare form of transformation, which is thought to occur due to a process of transdifferentiation whereby the lymphoma cells exhibit lineage plasticity and lose all evidence of B-cell phenotype and instead acquire the phenotype of a histiocytic neoplasm. Little is known about the underlying genetic alterations that occur during this unusual process. Comparative genetic analysis of pre- and post-transformation/transdifferentiation would be one tool by which we could better understand how this phenomenon occurs.

Case presentation

Here we report the clinical, immunophenotypic and genetic features of a rare case of secondary malignant histiocytosis, Langerhans cell-type (Langerhans cell sarcoma) arising from a previous low grade follicular lymphoma. FISH analysis confirmed the presence of IgH/BCL2 rearrangement in both the low grade follicular lymphoma (FL) and transformed Langerhans cells sarcoma (LCS) samples, demonstrating a clonal relationship. Comparative whole exome sequencing was then performed, which identified a KRAS p.G13D mutation in the LCS that was not present in the FL.

Conclusions

This report highlights genetic alterations, in particular an acquired somatic KRAS mutation, that may occur during transdifferentiation, with additional significance of KRAS mutation as a possible therapeutic target in cases which otherwise would have limited treatment options.

Electronic supplementary material

The online version of this article (10.1186/s13000-018-0758-0) contains supplementary material, which is available to authorized users.

Merkel cell polyomavirus and Langerhans cell neoplasm

BACKGROUND

The relationship between various external agents such as pollen, food, and infectious agents and human sensitivity exists and is variable depending upon individual's health conditions. For example, we believe that the pathogenetic potential of the Merkel cell polyomavirus (MCPyV), the resident virus in skin, is variable and depends from the degree of individual's reactivity. MCPyV as well as Epstein-Barr virus, which are normally connected with humans under the form of subclinical infection, are thought to be involved at various degrees in several neoplastic and inflammatory diseases. In this review, we cover two types of Langerhans cell neoplasms, the Langerhans cell sarcoma (LCS) and Langerhans cell histiocytosis (LCH), represented as either neoplastic or inflammatory diseases caused by MCPyV.

METHODS

We meta-analyzed both our previous analyses, composed of quantitative PCR for MCPyV-DNA, proteomics, immunohistochemistry which construct IL-17 endocrine model and interleukin-1 (IL-1) activation loop model, and other groups' data.

RESULTS

We have shown that there were subgroups associated with the MCPyV as a causal agent in these two different neoplasms. Comparatively, LCS, distinct from the LCH, is a neoplastic lesion (or sarcoma) without presence of inflammatory granuloma frequently observed in the elderly. LCH is a proliferative disease of Langerhans-like abnormal cells which carry mutations of genes involved in the RAS/MAPK signaling pathway. We found that MCPyV may be involved in the development of LCH.

CONCLUSION

We hypothesized that a subgroup of LCS developed according the same mechanism involved in Merkel cell carcinoma pathogenesis. We proposed LCH developed from an inflammatory process that was sustained due to gene mutations. We hypothesized that MCPyV infection triggered an IL-1 activation loop that lies beneath the pathogenesis of LCH and propose a new triple-factor model.

[The respiratory effects of smoking]

A marked increase in the morbidity and mortality of a large number of broncho-pulmonary diseases has been documented in relation to smoking. The influence of tobacco smoking on various respiratory conditions. is discussed: incidence, severity or natural history modification of some respiratory illnesses: obstructive lung diseases (COPD, asthma), lung cancer, bacterial, viral respiratory infections, with the impact of smoking on tuberculosis. Finally, the relationship of tobacco with diffuse interstitial lung disease: protective role of smoking (controversial in sarcoidosis, real in hypersensitivity pneumonitis). The benefits of smoking cessation are described.

Endocrine and metabolic assessment in adults with Langerhans cell histiocytosis

CONTEXT

Diabetes insipidus (DI) is one of most common complications of Langerhans cell histiocytosis (LCH) but prevalence of anterior pituitary deficiencies and metabolic alterations have not been clearly defined yet.

OBJECTIVES

Evaluate prevalence of endocrine and metabolic manifestations in a cohort of patients affected by Pulmonary LCH.

METHODS

Observational cross-sectional study on 18 adults (7 M/11 F, 42±12years) studied for complete basal and dynamic endocrine lab tests and glucose metabolism.

RESULTS

Hypothalamic-pituitary endocrine alterations were found in 9 patients: 9 had DI, 5 Growth Hormone Deficiency (GHD), 5 central hypogonadism, 3 central hypothyroidism and 1 central hypoadrenalism. Hyperprolactinemia and hypothalamic syndrome were found in 2 patients each. All these central endocrine alterations were always associated to DI. Five of the 10 MRI performed showed abnormalities. Prevalence of obesity and glucose alterations (either DM or IFG/IGT) were respectively 39% and 33%, higher than expected basing on epidemiological data on general Italian population. Multi-system-LCH without risk-organ involvement (LCH MS-RO^-) seems to have slightly higher prevalence of insulin resistance, glucose alterations and metabolic syndrome than LCH with isolated lung involvement (LCH SS lung⁺). A papillary BRAFV600E positive thyroid carcinoma was diagnosed in one patient.

CONCLUSIONS

The presence of anterior pituitary deficiencies should be systematically sought in all LCH patients with DI both at diagnosis and during the follow-up by basal and dynamic hormonal assessment. Patients with pulmonary LCH, particularly those with MS disease, have a worse metabolic profile than general population. Occurrence of papillary thyroid carcinoma has been reported.

Clinical implications of oncogenic mutations in pulmonary Langerhans cell histiocytosis

PURPOSE OF REVIEW

Langerhans cell histiocytosis (LCH) is a neoplasm of dendritic cells with a wide clinical spectrum. Localized pulmonary LCH occurs in young adults with a history of smoking and can either resolve spontaneously or lead to progressive decline in pulmonary function. Young children can also present with localized disease - frequently bone or skin - or with multifocal or multisystem disease. Clinical outcomes in these patients also vary widely, ranging from spontaneous resolution to multiorgan failure and death. This review describes recent developments in our understanding of the underlying pathogenesis of LCH and how these discoveries and other research are affecting how the disease is classified, treated and monitored.

RECENT FINDINGS

Somatic mutations resulting in activation of the mitogen-activated protein kinase (MAPK) pathway were recently identified as a key pathogenetic mechanism in both pediatric and pulmonary LCH.

SUMMARY

Knowledge of underlying pathogenetic mechanisms of LCH transforming how this disease and other histocytic/dendritic disorders are classified, treated and monitored.

COLD-PCR Technologies in the Area of Personalized Medicine: Methodology and Applications

Somatic mutations bear great promise for use as biomarkers for personalized medicine, but are often present only in low abundance in biological material and are therefore difficult to detect. Many assays for mutation analysis in cancer-related genes (hotspots) have been developed to improve diagnosis, prognosis, prediction of drug resistance, and monitoring of the response to treatment. Two major approaches have been developed: mutation-specific amplification methods and methods that enrich and detect mutations without prior knowledge on the exact location and identity of the mutation. CO-amplification at Lower Denaturation temperature Polymerase Chain Reaction (COLD-PCR) methods such as full-, fast-, ice- (improved and complete enrichment), enhanced-ice, and temperature-tolerant COLD-PCR make use of a critical temperature in the polymerase chain reaction to selectively denature wild-type-mutant heteroduplexes, allowing the enrichment of rare mutations. Mutations can subsequently be identified using a variety of laboratory technologies such as high-resolution melting, digital polymerase chain reaction, pyrosequencing, Sanger sequencing, or next-generation sequencing. COLD-PCR methods are sensitive, specific, and accurate if appropriately optimized and have a short time to results. A large variety of clinical samples (tumor DNA, circulating cell-free DNA, circulating cell-free fetal DNA, and circulating tumor cells) have been studied using COLD-PCR in many different applications including the detection of genetic changes in cancer and infectious diseases, non-invasive prenatal diagnosis, detection of microorganisms, or DNA methylation analysis. In this review, we describe in detail the different COLD-PCR approaches, highlighting their specificities, advantages, and inconveniences and demonstrating their use in different fields of biological and biomedical research.

Spontaneous pneumothorax in diffuse cystic lung diseases

PURPOSE OF REVIEW

Diffuse cystic lung diseases (DCLDs) are a heterogeneous group of disorders with varying pathophysiologic mechanisms that are characterized by the presence of air-filled lung cysts. These cysts are prone to rupture, leading to the development of recurrent spontaneous pneumothoraces. In this article, we review the epidemiology, clinical features, and management DCLD-associated spontaneous pneumothorax, with a focus on lymphangioleiomyomatosis, Birt-Hogg-Dubé syndrome, and pulmonary Langerhans cell histiocytosis.

RECENT FINDINGS

DCLDs are responsible for approximately 10% of apparent primary spontaneous pneumothoraces. Computed tomography screening for DCLDs (Birt-Hogg-Dubé syndrome, lymphangioleiomyomatosis, and pulmonary Langerhans cell histiocytosis) following the first spontaneous pneumothorax has recently been shown to be cost-effective and can help facilitate early diagnosis of the underlying disorders. Patients with DCLD-associated spontaneous pneumothorax have a very high rate of recurrence, and thus pleurodesis should be considered following the first episode of spontaneous pneumothorax in these patients, rather than waiting for a recurrent episode. Prior pleurodesis is not a contraindication to future lung transplant.

SUMMARY

Although DCLDs are uncommon, spontaneous pneumothorax is often the sentinel event that provides an opportunity for diagnosis. By understanding the burden and implications of pneumothoraces in DCLDs, clinicians can facilitate early diagnosis and appropriate management of the underlying disorders.

Major improvement in the detection of microsatellite instability in colorectal cancer using HSP110 T17 E-ice-COLD-PCR

Every colorectal cancer (CRC) patient should be tested for microsatellite instability (MSI) to screen for Lynch syndrome. Evaluation of MSI status involves screening tumor DNA for the presence of somatic deletions in DNA repeats using PCR followed by fragment analysis. While this method may lack sensitivity due to the presence of a high level of germline DNA, which frequently contaminates the core of primary colon tumors, no other method developed to date is capable of modifying the standard PCR protocol to achieve improvement of MSI detection. Here, we describe a new approach developed for the ultra-sensitive detection of MSI in CRC based on E-ice-COLD-PCR, using HSP110 T17, a mononucleotide DNA repeat previously proposed as an optimal marker to detect MSI in tumor DNA, and an oligo(dT)₁₆ LNA blocker probe complementary to wild-type genotypes. The HT17 E-ice-COLD-PCR assay improved MSI detection by 20-200-fold compared with standard PCR using HT17 alone. It presents an analytical sensitivity of 0.1%-0.05% of mutant alleles in wild-type background, thus greatly improving MSI detection in CRC samples highly contaminated with normal DNA. HT17 E-ice-COLD-PCR is a rapid, cost-effective, easy-to-implement, and highly sensitive method, which could significantly improve the detection of MSI in routine clinical testing.