Dramatic efficacy of vemurafenib in both multisystemic and refractory Erdheim-Chester disease and Langerhans cell histiocytosis harboring the BRAF V600E mutation

Advances in our understanding of genetic markers and targeted therapies for pediatric LCH

INTRODUCTION

Langerhans cell histiocytosis (LCH) is a rare myeloid neoplasm, encompassing a diverse clinical spectrum ranging from localized bone or skin lesions to a multisystemic life-threatening condition. Over the past decade, there has been an expansion in understanding the molecular biology of LCH, which translated into innovative targeted therapeutic approaches.

AREAS COVERED

In this article, we will review the molecular alterations observed in pediatric LCH and the relationship between these molecular changes and the clinical phenotype, as well as targeted therapies in LCH.

EXPERT OPINION

Mitogen-activated protein kinase (MAPK) pathway mutation is a hallmark of LCH and is identified in 80% of the cases. Notably, BRAFV600E mutation is seen in ~50-60% of the cases, ~30% has other MAPK pathway mutations, while 15-20% have no detected mutations. While the first line therapeutic approach is vinblastine and prednisone, targeted therapies - specifically BRAF/MEK inhibitors - emerged as a promising second-line salvage strategy, particularly when a mutation is identified. Most patients respond to BRAF/MEK inhibitors but at least 75% reactivate after stopping, however, most patients respond again when restarting inhibitors.

Patterns and organ treatment response of Erdheim-Chester disease with cardiac involvement

OBJECTIVE

To evaluate the heart response of Erdheim-Chester disease (ECD) through continuous follow-up within our large cohort, for which there is a lack of understanding.

METHODS

We conducted a retrospective analysis of clinical data from patients with ECD with cardiac involvement diagnosed at our centre between January 2010 and August 2023. We assessed the heart response by integrating pericardial effusion and metabolic responses.

RESULTS

A total of 40 patients were included, with a median age of 51.5 years (range: 29-66) and a BRAFV600E mutation rate of 56%. The most common imaging manifestations observed were pericardial effusion (73%), right atrium (70%) and right atrioventricular sulcus infiltration (58%). Among 21 evaluable patients, 18 (86%) achieved a heart response including 5 (24%) complete response (CR) and 13 (62%) partial response (PR). The CR rate of pericardial effusion response was 33%, while the PR rate was 56%. Regarding the cardiac mass response, 33% of patients showed PR. For cardiac metabolic response, 32% and 53% of patients achieved complete and partial metabolic response, respectively. There was a correlation between pericardial effusion response and cardiac metabolic response (r=0.73 (95% CI 0.12 to 0.83), p<0.001). The median follow-up was 50.2 months (range: 1.0-102.8 months). The estimated 5-year overall survival was 78.9%. The median progression-free survival was 59.4 months (95% CI 26.2 to 92.7 months). Patients who received BRAF inhibitors achieved better heart response (p=0.037) regardless of treatment lines.

CONCLUSION

We pioneered the evaluation of heart response of ECD considering both pericardial effusion and cardiac metabolic response within our cohort, revealing a correlation between these two indicators. BRAF inhibitors may improve heart response, regardless of the treatment lines.

Treatment of Cerebral Histiocytosis With Low Dose of Cobimetinib: A Report of 2 Cases

OBJECTIVES

Histiocytic disorders are pathologic expansions of myeloid cells in multiple organs, including the CNS. They share activation of the MAP kinase pathway due to either BRAFV600E variant or other variants in the RAS-RAF-MEK-ERK pathway. The rarity and heterogeneity of the disease only enable therapy through pathophysiologic considerations.

METHODS

We present 2 histiocytosis cases without BRAF sequence variants that affect the CNS, one with Erdheim-Chester disease and the other with an unspecified histiocytosis, and their diagnostic and therapeutic challenges.

RESULTS

In both cases, comprehensive analysis of the RAS-RAF-MEK-ERK signaling pathway secured the diagnosis. Treatment with the MEK inhibitor cobimetinib brought the disease to a complete halt. However, side effects such as thrombosis and serous macular edema made it necessary to reduce cobimetinib dosage. Low-dose cobimetinib maintenance medication was successful in preventing recurrence of histiocytic disease.

DISCUSSION

CNS involvement of histiocytic disorders can lead to detrimental neurologic symptoms. MEK inhibitors are effective treatment options for some of these patients. Since side effects are common, according to our cases we propose a low-dose treatment of 20 mg per day to balance treatment effects with side effects.

CLASSIFICATION OF EVIDENCE

This case report provides Class IV evidence. This is a single observational study without controls.

Treatment of congenital Langerhans cell histiocytosis with cobimetinib

We report a case of congenital multisystem Langerhans cell histiocytosis with cutaneous and hematopoietic involvement. After the failure of first-line (vinblastine and prednisolone) and second-line (vincristine and cytarabine) therapies, treatment with cobimetinib, a mitogen-activated protein kinase (MEK) inhibitor, led to the remission of disease and a sustained response after 11 months of ongoing treatment. Protein kinase inhibitors targeting BRAF or MEK could represent a promising future therapeutic option, also in children with LCH.

Multisystem Erdheim-Chester disease presenting with pericardial effusion confirmed by the effusion cytology specimen

Erdheim-Chester disease (ECD) is a rare histiocytosis characterized by the foamy CD68+CD1a- histiocytes infiltrating multiple organs and tissues. ECD might be asymptomatic or present with variable manifestations. The diagnosis of ECD requires characteristic radiological findings and pathological features. Herein, we described a 52-year-old female patient who was admitted to our hospital for recurrent pericardial effusion for two months. She has a medical history of papillary thyroid carcinoma (PTC) and underwent a total thyroidectomy two years before admission. The radiological findings suggested a potential diagnosis of ECD. Cytological analysis of the effusion cytology specimen revealed CD68+CD1a- histiocytes, confirming the ECD diagnosis. The BRAF V600E mutation was identified in the histiocytes, prompting the administration of vemurafenib, a BRAF inhibitor. After two months of standard-dose vemurafenib treatment, the disease was well controlled with pericardial effusion regression.

Erdheim-Chester Disease: Investigating the Correlation between Targeted Treatment Therapy and Disease Outcomes

A retrospective analysis of 20 adult patients with histopathological and clinical diagnoses of ECD was conducted at a single institution over a twenty-year period (2002-2022). Clinical responses were compared on the basis of treatments rendered, which included chemotherapy, immunotherapy, systemic corticosteroids, surgery and radiation, or targeted agents, referring to any small molecular inhibitors. Treatment response evaluation varied by the anatomic site(s) of disease, the extent of disease at diagnosis, and the imaging modality employed. In this analysis, patients were treated with a combination of targeted agents, myelosuppressive therapies, and radiation at various points in their disease courses. Of these, the most common treatment modality rendered was targeted therapy, employed in 11 of 20 patients. Partial responses or better were observed in 15 of 20 patients. Rates of stable disease trended towards being more frequent with targeted therapy versus conventional therapy but did not reach significance (p = 0.2967). Complete response rates trended towards being more common with conventional therapy than molecular (p = 0.5) but were equivocal overall. Trends of peripheral blood absolute monocytes with relation to disease activity were reviewed as recent literature implied that monocyte levels surrounding disease progression were of potential prognostic significance in histiocytic diseases. Amongst the patients who progressed at any point during their treatment course, absolute monocyte count (in K/µL) was identified at the closest available timepoint prior to or following disease progression and at the lowest value (nadir) following re-institution of therapy prior to any additional agent(s) being employed. There was no statistically significant difference in either of these monocyte values nor in disease outcomes with respect to treatments rendered within our cohort. However, our cohort consists of a heterogenous population of patients with ECD with data that highlights several trends over a longitudinal period, spanning the advent of targeted therapy. Significant differences are anticipated in ongoing analyses.

Skeletal involvement in Erdheim-Chester disease: Multimodality imaging features and association with the BRAFV600E mutation

OBJECTIVE

The aim of this study was to characterize the distribution of skeletal involvement in Erdheim-Chester disease (ECD) by using radiography, computed tomography (CT), 18F-FDG positron emission tomography/computed tomography (PET/CT), and bone scans, as well as looking for associations with the BRAFV600E mutation.

MATERIAL AND METHODS

Prospective study of 50 consecutive patients with biopsy-confirmed ECD who had radiographs, CT, 18F-FDG PET/CT, and Tc-99m MDP bone scans. At least two experienced radiologists with expertise in the relevant imaging studies analyzed the images. Summary statistics were expressed as the frequency with percentages for categorical data. Fisher's exact test, as well as odds ratios (OR) with 95 % confidence intervals (CI), were used to link imaging findings to BRAFV600E mutation. The probability for co-occurrence of bone involvement at different locations was calculated and graphed as a heat map.

RESULTS

All 50 cases revealed skeletal involvement at different regions of the skeleton. The BRAFV600E mutation, which was found in 24 patients, was correlated with femoral and tibial involvement on 18F-FDG PET/CT and bone scan. The appearance of changes on the femoral, tibial, fibular, and humeral involvement showed correlation with each other based on heat maps of skeletal involvement on CT.

CONCLUSION

This study reports the distribution of skeletal involvement in a cohort of patients with ECD. CT is able to detect the majority of ECD skeletal involvement. Considering the complementary nature of information from different modalities, imaging of ECD skeletal involvement is optimized by using a multi-modality strategy.

Dabrafenib and steroids for the treatment of Erdheim-Chester disease with extensive CNS involvement: a case report

Erdheim-Chester disease (ECD) is an exceedingly rare non-Langerhans cell CD68+ CD1a- S100- histiocytic multi-organ disease. Diagnosis of ECD is often delayed due to non-specific radiographic findings and heterogeneous lesional tissue. Increasingly, the role of genomic alterations is being recognized for both diagnosis and treatment of ECD. More than half of ECD patients harbor the BRAFV600E mutation. Evaluation for this mutation be can falsely negative on immunohistochemical staining and confirmation with molecular analyses is recommended. We present a case of the 44 year-old male with BRAFV600E-positive ECD treated successfully with steroids followed by single-agent dabrafenib.

A rare case report of Erdheim-Chester disease with pericardial effusion, conduction abnormalities, and atrial infiltration

Background

Erdheim-Chester disease (ECD) is a rare multisystem disorder that primarily affects adults. It is characterized by the excessive production and accumulation of histiocytes, a type of white blood cell, within multiple tissues and organs, including the cardiovascular system. The infiltration of histiocytes can cause a range of cardiovascular symptoms, including pericardial effusion, myocardial infiltration, and heart failure, among others. Despite the potential severity of these cardiovascular manifestations, ECD is often misdiagnosed or underdiagnosed, leading to delays in appropriate treatment and poor outcomes for patients. As such, there is a pressing need for increased awareness and understanding of ECD's cardiovascular manifestations among clinicians and researchers. This article aims to highlight the importance of considering ECD as a potential underlying cause of cardiovascular complaints and to encourage further investigation into this uncommon but potentially life-threatening condition.

Case summary

A 63-year-old man presented as outpatient complaining of dyspnoea on exertion during the last 3 weeks (New York Heart Association functional class III). He had also experienced a left shoulder and bilateral knee pain over the last 6 months. The patient was found to have a massive pericardial effusion associated with ECD. While pericardial effusions can have various causes, including infection, cancer, and autoimmune disorders, ECD is one potential cause of this condition. Therefore, it is important for clinicians to consider ECD in the differential diagnosis of patients presenting with unexplained pericardial effusions, particularly in the context of other systemic symptoms suggestive of ECD. We discuss about this specific aetiology and the clinical management of this uncommon condition.

Discussion

Erdheim-Chester disease, a non-Langerhans cell histiocytosis, is a rare multisystem disorder. Diagnosis is challenging and should be suspected in the presence of a pericardial effusion with conduction abnormalities with indicators of a multisystem disease.

Mutant PIK3CA is a targetable driver alteration in histiocytic neoplasms

Langerhans cell histiocytosis (LCH) is an inflammatory myeloid neoplasm characterized by the accumulation of clonal mononuclear phagocyte system cells expressing CD1a and CD207. In the past decade, molecular profiling of LCH as well as other histiocytic neoplasms demonstrated that these diseases are driven by MAPK activating alterations, with somatic BRAFV600E mutations in >50% of patients with LCH, and clinical inhibition of MAPK signaling has demonstrated remarkable clinical efficacy. At the same time, activating alterations in kinase-encoding genes, such as PIK3CA, ALK, RET, and CSF1R, which can activate mitogenic pathways independent from the MAPK pathway, have been reported in a subset of histiocytic neoplasms with anecdotal evidence of successful targeted treatment of histiocytoses harboring driver alterations in RET, ALK, and CSF1R. However, evidence supporting the biological consequences of expression of PIK3CA mutations in hematopoietic cells has been lacking, and whether targeted inhibition of PI3K is clinically efficacious in histiocytic neoplasms is unknown. Here, we provide evidence that activating mutations in PIK3CA can drive histiocytic neoplasms in vivo using a conditional knockin mouse expressing mutant PIK3CAH1047R in monocyte/dendritic cell progenitors. In parallel, we demonstrate successful treatment of PIK3CA-mutated, multisystemic LCH using alpelisib, an inhibitor of the alpha catalytic subunit of PI3K. Alpelisib demonstrated a tolerable safety profile at a dose of 750 mg per week and clinical and metabolic complete remission in a patient with PIK3CA-mutated LCH. These data demonstrate PIK3CA as a targetable noncanonical driver of LCH and underscore the importance of mutational analysis-based personalized treatment in histiocytic neoplasms.

The clinical spectrum and prognostic factors of Erdheim-Chester disease and mixed Langerhans cell histiocytosis and Erdheim-Chester disease

Erdheim-Chester disease (ECD) is a rare and probably fatal multisystemic non-Langerhans cell histiocytosis (LCH). To comprehensively investigate the clinical features, genomic analysis, treatments, and prognostic factors of ECD, we retrospectively analyzed the clinical data of 75 ECD patients and 10 mixed LCH and ECD patients in our center. The median age at diagnosis was 46 years (range, 5-70). ECD patients were older at diagnosis (p = 0.006) and had more cardiac involvement (p = 0.011) as well as vascular (p = 0.031) involvement compared to mixed LCH and ECD patients. 64.8% of ECD patients and 87.5% of mixed LCH and ECD patients carried BRAFV600E mutation. The BRAFV600E mutation correlated with a greater number of affected organs (p = 0.030) and was associated with lung involvement (p = 0.033) as well as pleural involvement (p = 0.002). The median follow-up time was 38 months (range, 1-174). The estimated 5-year progression-free survival (PFS) and overall survival (OS) were 48.9% and 84.7%, respectively. In a multivariate analysis, right atrial pseudotumor (p = 0.013) and pancreatic involvement (p = 0.005) predicted worse OS, while pleural (p = 0.042) and central nervous system (CNS) involvement (p = 0.043) predicted worse PFS. Our study described the clinical spectrum of ECD and mixed LCH and ECD, while also revealed the prognostic value of right atrial pseudotumor and pancreatic, pleural, and CNS involvement for worse survival.

Histiocytic neoplasms: Going, going, but not quite gone

BRAF and MEK inhibitors have revolutionised the treatment of patients with high-risk histiocytic neoplasms but does a complete response mean that treatment can be withdrawn? Commentary on: Reiner et al. Outcomes after interruption of targeted therapy in patients with histiocytic neoplasms. Br J Haematol 2023;203:389-394.

Single-system pulmonary langerhans cell histiocytosis with only tracheobronchial involvement: a case report

BACKGROUND

Pulmonary Langerhans cell histiocytosis (PLCH) only with airway involvement manifested as diffuse thickening of the tracheobronchial walls is rare.

CASE REPORT

A 26-year-old male was admitted to the hospital with progressive wheezing, cough, and a source of blood in sputum after activity. He had no history of smoking. Chest computed tomography showed airway stenosis of different degrees with tracheobronchial wall thickening, and fiberoptic bronchoscopy demonstrated multiple nodular neoplasms in tracheobronchial, while the pulmonary parenchyma was normal. The patient's condition partially improved after excision of partial lesions by fiberoptic bronchoscope. Histopathological results showed that CD1a and S-100 immunohistochemical staining was positive, and the molecular pathological results suggested that the BRAF V600E mutation, thus confirming the diagnosis of PLCH. The treatment of partial resection and systemic chemotherapy is effective.

CONCLUSIONS

The possibility of PLCH needs to be considered when diffuse tracheobronchial lesions without lung parenchyma involvement are encountered, which provides experience for early clinical diagnosis and adequate treatment.

[Histiocytosis]

Histiocytosis is a group of rare diseases characterized by inflammation and accumulation of cells derived from monocytes and macrophages in different tissues. The symptoms are highly variable, from mild forms with involvement of a single organ to severe multisystem forms that can be life compromising. The diagnosis of histiocytosis is based on the clinic, radiological findings and pathological anatomy. A biopsy of the affected tissue is recommended in all cases as it may have therapeutic implications. During the last decade, some mutations have been identified in the affected tissue that condition activation of the MAPK/ERK and PI3K/AKT pathway, in a variable proportion depending on the type of histiocytosis. In this review we mainly focus on Langerhans Cell Histiocytosis, Erdheim-Chester Disease and Rosai-Dorfman Disease.

An Unusual Case of Erdheim Chester Disease (ECD) with Knee Pain: A Case Report

Background: Erdheim Chester disease (ECD) is a rare, non-Langerhans cell histiocytosis of unknown etiology that occurs in multiple organs. The clinical characteristics of ECD are unknown, making it difficult to diagnose. Case presentation: A 61-year-old woman presented with left knee pain and contracture. She had recent medical problems such as recurrent urinary tract infection, pericardial effusion, and pleural effusion. Simple radiography and magnetic resonance imaging of the knee revealed an osteosclerotic lesion. Under suspicion of malignancy, other radiologic modalities were performed, but there were no significant results showing malignancy. A bone biopsy of the knee lesion led to a final diagnosis of ECD. The patient was treated with systemic steroids and was ultimately tried on PEG-interferon. Conclusion: This report describes an unusual presentation of ECD involving the skeletal system and multiple extraskeletal organs. Owing to its non-specific nature, ECD was notably difficult to diagnose. Therefore, if a patient has knee pain and other multiorgan presentations without malignancy, clinicians should suspect ECD.

Prevalence, patterns and outcomes of cardiac involvement in Erdheim-Chester disease

AIMS

Cardiac involvement of Erdheim-Chester disease (ECD), a rare L group histiocytosis, has been reported to be associated with poor outcomes, but systematic studies are lacking. The present study aimed to investigate the prevalence, clinical features, imaging features, and prognosis of cardiac involvement in ECD in a large series.

METHODS AND RESULTS

All patients with ECD who underwent cardiac magnetic resonance (CMR) imaging between 2003 and 2019 at a French tertiary center were retrospectively included. Primary outcome was all-cause mortality. Secondary outcomes were pericarditis, cardiac tamponade, conduction disorders, device implantation and coronary artery disease (CAD). A total of 200 patients were included [63 (54-71) years, 30% female, 58% BRAFV600E mutated]. Median follow-up was 5.5 years (3.3-9 years). On CMR, right atrioventricular sulcus infiltration was observed in 37% of patients, and pericardial effusion was seen in 24% of patients. In total, 8 patients (4%) had pericarditis (7 acute, 1 constrictive), 10 patients (5%) had cardiac tamponade, 5 patients (2.5%) had ECD-related high-degree conduction disorders, and 45 patients (23%) had CAD. Overall, cardiac involvement was present in 96 patients (48%) and was associated with BRAFV600E mutation [Odds ratio (OR) = 7.4, 95% confidence interval (CI) (3.5-16.8), P < 0.001] and ECD-related clinical events [OR = 5, 95%CI (1.5-21.2), P = 0.004] but not with lower survival in multivariate analysis [adjusted hazard ratio (HR) = 1.4, 95% CI (0.8-2.5), P = 0.2].

CONCLUSION

Cardiac involvement is present in nearly half of ECD patients and is associated with BRAFV600E mutation and complications (pericarditis, cardiac tamponade, and conduction disorders) but not with lower survival.

Erdheim-Chester disease and vemurafenib: a review of ophthalmic presentations and clinical outcomes

PURPOSE

To provide a comprehensive review of ocular and orbital manifestations of Erdheim-Chester Disease (ECD) and compare clinical outcomes with vemurafenib (INN) to historical treatments (HT). Primary outcomes are ophthalmic findings on presentation, changes in visual acuity, and mortality rate. Secondary outcomes include the progression of ocular findings, systemic involvements, and treatment modalities.

METHODS

All published literature from January 1983 to March 2021 was searched for ophthalmic manifestations of ECD. Clinical outcomes following HT were collected and compared with INN.

RESULTS

Forty-seven patients with ECD and ophthalmic presentations were identified. The mean age was 49.6 years (SD = 15.0). Proptosis (65.6%) and extraocular muscle restrictions (42.5%) were the most common presenting signs. Of 41 (87.2%) patients with orbital masses on radiologic examination, 90.2% were bilateral, and 53.7% were located in the intraconal space. Ophthalmic examination was significant for xanthelasma (27.2%), optic disc edema (34.0%), and subretinal changes (21.3%). Common treatments were systemic steroids (76.6%), interferon-α (17.0%), and cyclophosphamide (14.9%). INN was less commonly used (12.8%). The mean change in logMAR visual acuity declined with HT (29.9%) but improved with INN (79.1%) (p > 0.05). The proportion of eyes with complete vision loss increased after HT (p < 0.05). The overall mortality rate was 27.7% and notably higher in the HT group (29.3%) when compared to the INN group (16.7%) (p > 0.05).

CONCLUSION

ECD presents with many ophthalmic manifestations. Although the intraocular treatments remain controversial, INN should be highly considered in treating orbital ECD patients with BRAF-V600E mutations to prevent and reverse vision loss.

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.

Erdheim–Chester Disease of the Breast: First Review and First Case of Isolated Severe Gynecomastia

(1) Introduction: Erdheim–Chester disease (ECD) is a life-threatening condition and often a diagnostic challenge. It has recently been classified as a hematopoietic tumour, and the cases of ECD reported in the literature has dramatically increased during the last 15 years. (2) Methods: We describe the case of a 57-year-old male patient with severe gynecomastia, with a detailed description of his diagnostic iter and consequent surgical operation. We provide the first systematic review of the literature of breast involvement in ECD, following PRISMA guidelines, including 13 studies and 16 patients. (3) Results: Our report resulted to be the first case of gynecomastia as a single clinical and imaging feature of ECD described in English literature. A total of 81.3% of patients included were female. Among them, 76.9% had unilateral and nodular presentation, while male patients presented bilateral heterogeneous breast enlargement. Globally, 87.5% expressed breast alterations as their first manifestations of ECD. Only 50% presented skeletal involvement. (4) Conclusion: The reported case represents a unique addition to the literature. We found two different patterns in ECD-related breast involvement between male and female patients, an unusual M/F ratio, and a lower rate of bone involvement. Breast involvement is frequently the first clinical feature; therefore, breast caregivers should be aware of this dangerous and most likely underestimated condition.

Efficacy and safety of vemurafenib in Langerhans cell histiocytosis (LCH): A systematic review and meta-analysis

Almost half of the patients with Langerhans cell histiocytosis (LCH) are refractory to primary induction chemotherapy or undergo reactivation. The ideal treatment modality for refractory/relapsed LCH is yet not evidenced. This review aimed to determine the efficacy and safety of vemurafenib (a BRAF pathway inhibitor) in LCH, particularly the refractory/relapsed cases. The literature search was conducted using PubMed, Embase, CENTRAL, and abstracts published in the SIOP meetings. Studies that described the outcome of patients of LCH being treated with vemurafenib, alone or in combination, were included. A total of 416 studies were screened, and after applying exclusion criteria, 22 studies (n = 107) were included in the final analysis. The first-line therapy was prednisolone plus vinblastine for most patients (n = 92, 86%), and vemurafenib was started upfront in 3 patients (3%). The median time to first clinical response with vemurafenib was one week. The median time to best response was 5.25 months. Out of 107 patients, 62 patients (58%) had ultimately no active disease (NAD) while 39 (36%) had active disease better (ADB), making the overall response rate (ORR) of 101/107, ie, 94.4% (CI 0.88; 0.98). The main adverse effects of vemurafenib were rash or photosensitivity (47%) and other cutaneous adverse events (15%). Vemurafenib is highly efficacious and safe in the treatment of refractory LCH; however, the timing of its commencement and duration of therapy is yet to be established. Larger prospective collaborative trials are needed to answer the appropriate treatment duration and effective maintenance therapy approach.

Genomic profiling for clinical decision making in lymphoid neoplasms

With the introduction of large-scale molecular profiling methods and high-throughput sequencing technologies, the genomic features of most lymphoid neoplasms have been characterized at an unprecedented scale. Although the principles for the classification and diagnosis of these disorders, founded on a multidimensional definition of disease entities, have been consolidated over the past 25 years, novel genomic data have markedly enhanced our understanding of lymphomagenesis and enriched the description of disease entities at the molecular level. Yet, the current diagnosis of lymphoid tumors is largely based on morphological assessment and immunophenotyping, with only few entities being defined by genomic criteria. This paper, which accompanies the International Consensus Classification of mature lymphoid neoplasms, will address how established assays and newly developed technologies for molecular testing already complement clinical diagnoses and provide a novel lens on disease classification. More specifically, their contributions to diagnosis refinement, risk stratification, and therapy prediction will be considered for the main categories of lymphoid neoplasms. The potential of whole-genome sequencing, circulating tumor DNA analyses, single-cell analyses, and epigenetic profiling will be discussed because these will likely become important future tools for implementing precision medicine approaches in clinical decision making for patients with lymphoid malignancies.

Histiocytic Disorders of Childhood

Histiocytic disorders of childhood represent a wide spectrum of conditions that share the common histologic feature of activated or transformed "histiocytes." Langerhans cell histiocytosis (LCH) is the most common, with an incidence of approximately 5 per million children. LCH may be difficult to distinguish from more ubiquitous causes of skin rashes, bone pain, or fever. Current chemotherapy fails to cure more than 50% of children with multifocal disease, and treatment failure is associated with increased risks of long-term sequelae. Somatic activating mitogen-activated protein kinase (MAPK) pathway-activating mutations (most often BRAFV600E) have been identified in hematopoietic precursors in patients with LCH. Opportunities to improve outcomes with targeted therapies are under investigation. Juvenile xanthogranuloma (JXG) and Rosai-Dorfman disease (RDD) are less common than LCH and are distinguished by specific histologic and clinical features. Recurrent MAPK pathway gene mutations are also identified in JXG and RDD. In many cases, these conditions spontaneously resolve, but disseminated disease can be fatal. Although there has been historic debate regarding the nature of these conditions as inflammatory versus neoplastic, LCH, JXG, and RDD are now considered myeloid neoplastic disorders. In contrast, hemophagocytic lymphohistiocytosis (HLH) is clearly a disorder of immune dysregulation. HLH is characterized by extreme immune activation driven by hyperactivated T cells. HLH arises in approximately 1 child per million and is nearly universally fatal without prompt recognition and immune suppression. Outcomes of treated children are poor, with approximately 60% survival. Emapalumab, which targets interferon-γ signaling, was recently approved for patients with recurrent or refractory HLH, and additional cytokine-directed therapies are under investigation.

Integrated imaging of systemic Langerhans cell histiocytosis in an infant

Langerhans cell histiocytosis (LCH) is a myeloid neoplasm characterized by a clonal proliferation of CD1a+/CD207+ dendritic cells. Although individuals of any age can be affected, the disease is most common in infants younger than 5 years of age, especially males. A wide range of manifestations, from asymptomatic to aggressive, have been described, along with multiorgan involvement. Even though the majority of bone lesions are observed, skin, lymph nodes, brain and lungs can also be involved. The involvement of hematopoietic system, including bone marrow, liver and spleen, is less frequent yet associated with worse prognosis, due to a worse treatment response. Diagnosis of LCH is based on the integration of clinical, laboratory, and radiological data; however, only histopathological examination might confirm it. As far as the spleen involvement is concerned, according to literature, it has been reported in about 15% patients with multisystem involvement, nonetheless only a few cases show parenchymal lesions. The present study reports the case of an infant with LCH with multisystem involvement, including bone, skin, liver, and spleen, with evidence of parenchymal lesions.

A rare case of Erdheim-chester disease reported from Nepal

Introduction

Erdheim-Chester Disease (ECD) is a rare non-Langerhans cell histiocytosis with a propensity to involve multiple organs.

Case presentation

We report a case of a patient in mid-60s with occipital headache and ataxia. Following the radiological and immunohistochemical investigations and genomic studies, a diagnosis of ECD was made with two intracerebral lesions. Brain lesions were resected and the patient was discharged with the medication Vemurafenib. After 3 years of diagnosis and 13 years of initial presentation, patient passed away.

Discussion

ECD frequently presents with Diabetes Insipidus as initial presentation, long bone osteosclerosis as the most common presentation, and has multi-system predisposition. ECD can be differentiated from Langerhans Cell Histiocytosis (LCH) with immunohistochemistry images of the biopsy specimens. Further, with genomic analysis of ECD, the neoplastic nature has been highlighted and targeted therapies like Vemurafenib and Cobimetinib are shown to be effective.

Conclusion

Good clinical judgement and supporting investigations can aid in diagnosing rare entities like ECD even in resource-limited settings.

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Rare case of Erdheim-Chester disease with multi-system involvement presenting with initial features 10 years prior to diagnosis.

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Initially Diabetes Insipidus, followed by long bone and other multi-system involvement important cues for the diagnosis.

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Biopsy of the lesion and immunohistochemical analysis can help confirm the diagnosis.

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Genomic studies with mutational analysis further highlights the neoplastic nature of the disease.

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Advancement of genomic studies with targeted therapies like Vemurafenib and Cobimetinib key in of management of ECD.

Extensive Aortic Thromboembolism in a Patient With Erdheim-Chester Disease: A Case Report

Background

Erdheim-Chester disease (ECD) is a rare disease that affects multiple systems and is characterized by non-Langerhans cell histiocytosis. Classic clinical signs include long bone infiltration, central nervous system involvement, diabetes insipidus, and sheathing of the entire aorta. However, thrombosis is not recognized as a typical cardiac manifestation of ECD. Here, we report the case of an ECD patient with extensive arterial thrombus formation and embolism in several sections of the aorta.

Case

A 36-year-old woman was admitted due to recurrent fever and left finger cyanosis for 20 days. Laboratory tests revealed that her C-reactive protein and interleukin-6 levels were significantly elevated. Thoracic computed tomographic angiography (CTA) revealed thrombosis from the aortic arch to the left subclavian artery accompanied by severe stenosis of the left subclavian artery. Abdominal CTA revealed splenic infarction due to splenic artery embolism and thrombus formation in multiple abdominal arteries. She underwent emergent arterial thrombectomy. During hospitalization, she complained of polyuria. The desmopressin test and pituitary magnetic resonance imaging findings suggested diabetes insipidus. Furthermore, positron emission tomography-computed tomography and bone emission computed tomography showed long bone impairment, and pathological examination of the bone samples confirmed ECD. Steroids and tocilizumab were selected as the initial therapies; however, thrombosis continued to develop. After replacement of tocilizumab with interferon-α, her condition became stable.

Conclusion

Although extremely rare, fatal thrombosis may be a significant cardiovascular manifestation of ECD.

A Rare Case of Pediatric Xanthoma Disseminatum With Diabetes Insipidus and BRAF p.V600E Mutation

ABSTRACT

Xanthoma disseminatum (XD) is a rare non-Langerhans cell histiocytosis characterized by xanthomatous lesions in the absence of hyperlipidemia. XD usually develops in young adults, and there are rare cases among children. BRAF mutations are frequent in Langerhans cell histiocytosis and Erdheim-Chester disease but absent or only rarely detected in other histiocytosis. Herein, we described a 6-year-old Chinese girl presented with generalized skin lesions and diabetes insipidus for 5 months. There were multiple periorbital xanthelasma with histopathological features of foamy histiocytes infiltration with Touton cells. Pituitary magnetic resonance imaging showed pituitary enlargement and pituitary stalk thickening. The presence of BRAF p.V600E mutation makes this case distinctive and also offers a potential therapeutic target. According to our review of the literature, this is the first pediatric XD with diabetes insipidus and BRAF mutation.

Near Complete Response to Trametinib Treatment in Histiocytic Sarcoma Harboring a Somatic KRAS Mutation

Survival outcomes of patients with histiocytic neoplasms are poor, with no standard-of-care treatments available for these malignancies. Recent characterization of the genomic landscape of various histiocytic neoplasms have shown a predominance of activating driver mutations within the MAPK/ERK pathway (ie, BRAF, MEK, KRAS, MAPK, and NRAS). Subsequently, successful treatment of these malignancies with BRAF and MEK inhibitors has been reported. This report presents the first patient with histiocytic sarcoma harboring a somatic KRAS Q61H mutation who was subsequently treated to a near complete response with the MEK inhibitor trametinib. Due to patient preference, lack of standard of care treatments, and associated morbidity from head and neck dissection, initial disease reduction provided by trametinib therapy allowed for a less morbid resection. This case report highlights the utility of up-front next-generation sequencing and the efficacy of MEK inhibition in patients with histiocytic sarcoma harboring activating KRAS mutations.

Skull Base Tumors: Neuropathology and Clinical Implications

Tumors that arise in and around the skull base comprise a wide range of common and rare entities. Recent studies have advanced our understanding of their pathogenesis, which in some cases, have significantly influenced clinical practice. The genotype of meningiomas is strongly associated with their phenotype, including histologic subtype and tumor location, and clinical outcome. A single molecular alteration, NAB2-STAT6 fusion, has redefined the category of solitary fibrous tumors to include the previous entity hemangiopericytomas. Schwannomas, both sporadic and familial, are characterized by near ubiquitous alterations in NF2 , with additional mutations in SMARCB1 or LZTR1 in schwannomatosis. In pituitary adenohypophyseal tumors, cell lineage transcription factors such as SF-1, T-PIT, and PIT-1 are now essential for classification, providing a more rigorous taxonomy for tumors that were previously considered null cell adenomas. The pituicyte lineage transcription factor TTF-1 defines neurohypophyseal tumors, which may represent a single nosological entity with a spectrum of morphologic manifestations (ie, granular cell tumor, pituicytoma, and spindle cell oncocytoma). Likewise, the notochord cell lineage transcription factor brachyury defines chordoma, discriminating them from chondrosarcomas. The identification of nonoverlapping genetic drivers of adamantinomatous craniopharyngiomas and papillary craniopharyngiomas indicates that these are distinct tumor entities and has led to successful targeted treatment of papillary craniopharyngiomas using BRAF and/or mitogen-activated protein kinase inhibitors. Similarly, dramatic therapeutic responses have been achieved in patients with Langerhans cell histiocytosis, both with BRAF -mutant and BRAF -wildtype tumors. Familiarity with the pathology of skull base tumors, their natural history, and molecular features is essential for optimizing patient care.

Erdheim-Chester disease with multisystem involvement evaluated by multimodal imaging: A case report

Erdheim-Chester disease is a rare, idiopathic, multisystemic non-Langerhans cell histiocytosis. Little is known about the imaging features. Herein, we report a very uncommon case of Erdheim-Chester disease in a 54-year-old woman with multisystem involvement including cardiovascular system, skeleton, retroperitoneum (renal and adrenal infiltration), orbit and pituitary. Multimodal imaging modalities, including computed tomography, magnetic resonance imaging, echocardiography, and bone scintigraphy were used to comprehensively evaluate different organs involvement. Finally, myocardial biopsy results indicated Erdheim-Chester disease. Electrocardiography showed sick sinus syndrome and slowest heart rate of 20 beats/min. The patient underwent permanent pacemaker implantation and had initial treatment with interferon. There were no remarkable changes in right atrial lesion during 9-month follow-up period. Erdheim-Chester disease was a rare entity with a dismal prognosis, especially when there were cardiac and neurological involvement. The present case report aimed to described and analyzed radiological findings of multiple organs involvement of Erdheim-Chester disease with multimodal imaging retrospectively, and being familiar with the imaging features of Erdheim-Chester disease might help prompt and correct diagnosis of this disease in the future.

Endoscopic Transsphenoidal Resection of Suprasellar Histiocytosis in a Patient with Erdheim-Chester Disease: A Case Report

Erdheim–Chester disease (ECD) is a rare systemic disease characterized by non-Langerhans histiocytosis. Pituitary involvement, often manifesting as diabetes insipidus, is the most common central nervous system (CNS) lesion. However, significant mass formation compressing the optic apparatus is rarely reported. We present a case of ECD-related suprasellar mass treated with an endoscopic transnasal approach, with emphasis on the surgical strategy and the intraoperative findings. The mass was fibrous, significantly hard, and strongly adhered to the optic nerves, causing visual impairment. A subtotal resection was performed with preserving the adhesion between the mass and the optic nerves, and her visual symptoms improved remarkably after surgery. We highlight the surgical procedure of ECD-related suprasellar mass, from an endoscopic point of view. Due to strong adhesion of the mass to the surrounding optic apparatus and perforators, complete resection may be harmful; judicious mass reduction with preserving such adhesion would contribute to better visual outcomes.

ALK-positive histiocytosis: a new clinicopathologic spectrum highlighting neurologic involvement and responses to ALK inhibition

ALK-positive histiocytosis is a rare subtype of histiocytic neoplasm first described in 2008 in 3 infants with multisystemic disease involving the liver and hematopoietic system. This entity has subsequently been documented in case reports and series to occupy a wider clinicopathologic spectrum with recurrent KIF5B-ALK fusions. The full clinicopathologic and molecular spectra of ALK-positive histiocytosis remain, however, poorly characterized. Here, we describe the largest study of ALK-positive histiocytosis to date, with detailed clinicopathologic data of 39 cases, including 37 cases with confirmed ALK rearrangements. The clinical spectrum comprised distinct clinical phenotypic groups: infants with multisystemic disease with liver and hematopoietic involvement, as originally described (Group 1A: 6/39), other patients with multisystemic disease (Group 1B: 10/39), and patients with single-system disease (Group 2: 23/39). Nineteen patients of the entire cohort (49%) had neurologic involvement (7 and 12 from Groups 1B and 2, respectively). Histology included classic xanthogranuloma features in almost one-third of cases, whereas the majority displayed a more densely cellular, monomorphic appearance without lipidized histiocytes but sometimes more spindled or epithelioid morphology. Neoplastic histiocytes were positive for macrophage markers and often conferred strong expression of phosphorylated extracellular signal-regulated kinase, confirming MAPK pathway activation. KIF5B-ALK fusions were detected in 27 patients, whereas CLTC-ALK, TPM3-ALK, TFG-ALK, EML4-ALK, and DCTN1-ALK fusions were identified in single cases. Robust and durable responses were observed in 11/11 patients treated with ALK inhibition, 10 with neurologic involvement. This study presents the existing clinicopathologic and molecular landscape of ALK-positive histiocytosis and provides guidance for the clinical management of this emerging histiocytic entity.

A long-term survival case of Erdheim-Chester disease on maintenance hemodialysis

Erdheim-Chester disease, a rare non-Langerhans histiocytosis, involves multiple organs, including kidney. Renal dysfunction sometimes occurs, and is attributed to ureteral obstruction and renal artery stenosis by histiocytic infiltration. However, to our knowledge, case reports of end-stage renal disease requiring renal replacement therapy due to Erdheim-Chester disease are very few. Here, we report a 69-year-old woman who was diagnosed with Erdheim-Chester disease 10 years ago. She had multiple organ involvement, such as bone, skin, heart, pituitary gland, kidney, and retroperitoneum. She had been treated with interferon-alpha, but discontinued after 2 years due to depression and repeated infection. She did not desire treatment with other drugs, so we continued supportive care. Her renal function gradually deteriorated, and hemodialysis was initiated 4 years ago. Subsequently, she is still doing well without any major symptoms. This report describes an unusual case of Erdheim-Chester disease requiring maintenance hemodialysis that longer prognosis than expected was obtained regardless of multiple organ involvement and no specific treatment after interferon-alpha cessation.

Multi-System Langerhans Cell Histiocytosis as a Mimic of IgG4-Related Disease: A Case Report and Literature Review

Langerhans cell histiocytosis (LCH) is a rare disease characterized by the clonal accumulation and/or proliferation of specific dendritic cells resembling normal epidermal Langerhans cells (LCs). Clinical manifestations are variable, depending on the affected tissues or organs, however, LCH with elevated serum IgG4 has not been reported. Herein, we reported a 26-year-old Chinese female multi-system LCH (MS-LCH) who first presented with central diabetes insipidus (CDI), accompanied by panhypopituitarism and hepatic dysfunction. Diagnostic investigations were strongly suspicious of IgG4-RD because of elevated serum IgG4 levels during the process. Furtherly, thyroid and lymph node involvement and biopsy led to the diagnosis of MS-LCH; the strongly positive staining of CD1a, S100, CD207 (langerin), and Ki67 was found. Moreover, after systemic treatment with five cycles of chemotherapy, many lesions were greatly improved. Since both LCH and IgG4-RD are orphan diseases that can affect any organ, the differential diagnosis is challenging, especially when LCH is associated with unexplained serum IgG4 elevation. In this article, the case of a young woman suffering from MS-LCH that affected organs including the pituitary, thyroid, lymph node, and liver was summarized, and relevant literature was reviewed to better equip the diagnosis and treatment in its early stages.

Solitary Radiolucent Erdheim-chester Disease: A Case Report and Literature Review

Background:

Erdheim-chester disease (ECD) is a rare non-Langerhans histiocytosis of unknown etiology, which typically presents with bilateral symmetric osteosclerosis and multi-organ involvement. Lesions may be intraosseous or extraosseous and involve the heart, pulmonary system, CNS, and skin in order of decreasing likelihood.

Objective:

The objective of this study is to discuss a case of erdheim-chester disease and conduct a review of the literature.

Case:

We describe a rare case of erdheim-chester in an asymptomatic 37-year-old male who was diagnosed after suffering a right ulnar injury. Subsequent evaluation revealed a solitary radiolucent ulnar lesion without multi-system involvement.

Results & Conclusion:

The case is unique in its solitary distribution, lytic radiographic appearance, and asymptomatic presentation preceding pathologic fracture. This presentation may simulate multiple other bone lesions.

Somatic Mutations in Rheumatologic Diseases: VEXAS Syndrome and Beyond

Discovery of the VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) syndrome demonstrates that somatic mutations in hematologic precursor cells can cause adult-onset, complex inflammatory disease. Unlike germline mutations, somatic mutations occur throughout the lifespan, are restricted to specific tissue types, and may play a causal role in non-heritable rheumatologic diseases, especially conditions that start in later life. Improvements in sequencing technology have enabled researchers and clinicians to detect somatic mutations in various tissue types, especially blood. Understanding the relationships between cell-specific acquired mutations and inflammation is likely to yield key insights into causal factors that underlie many rheumatologic diseases. The objective of this review is to detail how somatic mutations are likely to be relevant to clinicians who care for patients with rheumatologic diseases, with particular focus on the pathogenetic mechanisms of the VEXAS syndrome.

Urologic Manifestations and Hydronephrosis as Initial Presentation of Erdheim-Chester Disease: A Rare Form of Non-Langerhans Histiocytosis

Erdheim-Chester disease (ECD) is a rare non-Langerhans histiocytosis that is classified as a malignancy of myeloid progenitor cells, with only 1,000 confirmed cases in the literature so far. It often manifests as a multi-system disorder with an initial presentation predominantly in the long bones, central nervous system (CNS), and retroperitoneal space, sometimes causing urologic symptoms as a result. ECD often presents indolently and in a spectrum of different ways, making it challenging to identify and treat. We report a case of a 63-year-old female with ECD that first presented with abdominal pain and acute renal injury due to ECD-related retroperitoneal fibrosis. We also explore the literature at large around ECD, its diagnosis, pathophysiology, and advances in treatments.

Cancer gene mutation frequencies for the U.S. population

Mutations play a fundamental role in the development of cancer, and many create targetable vulnerabilities. There are both public health and basic science benefits from the determination of the proportion of all cancer cases within a population that include a mutant form of a gene. Here, we provide the first such estimates by combining genomic and epidemiological data. We estimate KRAS is mutated in only 11% of all cancers, which is less than PIK3CA (13%) and marginally higher than BRAF (8%). TP53 is the most commonly mutated gene (35%), and KMT2C, KMT2D, and ARID1A are among the ten most commonly mutated driver genes, highlighting the role of epigenetic dysregulation in cancer. Analysis of major cancer subclassifications highlighted varying dependencies upon individual cancer drivers. Overall, we find that cancer genetics is less dominated by high-frequency, high-profile cancer driver genes than studies limited to a subset of cancer types have suggested.

Understanding the frequency of gene mutations in cancer could be important for generating targeted therapeutics. Here, the authors use SEER data and cancer genomics data from TCGA to estimate the gene mutation frequencies in the US cancer population.

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.

The Dual Role of Autophagy in Crizotinib-Treated ALK+ ALCL: From the Lymphoma Cells Drug Resistance to Their Demise

Autophagy has been described as harboring a dual role in cancer development and therapy. Depending on the context, it can exert either pro-survival or pro-death functions. Here, we review what is known about autophagy in crizotinib-treated ALK⁺ ALCL. We first present our main findings on the role and regulation of autophagy in these cells. Then, we provide literature-driven hypotheses that could explain mechanistically the pro-survival properties of autophagy in crizotinib-treated bulk and stem-like ALK⁺ ALCL cells. Finally, we discuss how the potentiation of autophagy, which occurs with combined therapies (ALK and BCL2 or ALK and RAF1 co-inhibition), could convert it from a survival mechanism to a pro-death process.

Single-Cell Profiling Reveals Metabolic Reprogramming as a Resistance Mechanism in BRAF-Mutated Multiple Myeloma

PURPOSE

Although remarkably effective in some patients, precision medicine typically induces only transient responses despite initial absence of resistance-conferring mutations. Using BRAF-mutated myeloma as a model for resistance to precision medicine we investigated if BRAF-mutated cancer cells have the ability to ensure their survival by rapidly adapting to BRAF inhibitor treatment.

EXPERIMENTAL DESIGN

Full-length single-cell RNA (scRNA) sequencing (scRNA-seq) was conducted on 3 patients with BRAF-mutated myeloma and 1 healthy donor. We sequenced 1,495 cells before, after 1 week, and at clinical relapse to BRAF/MEK inhibitor treatment. We developed an in vitro model of dabrafenib resistance using genetically homogeneous single-cell clones from two cell lines with established BRAF mutations (U266, DP6). Transcriptional and epigenetic adaptation in resistant cells were defined by RNA-seq and H3K27ac chromatin immunoprecipitation sequencing (ChIP-seq). Mitochondrial metabolism was characterized by metabolic flux analysis.

RESULTS

Profiling by scRNA-seq revealed rapid cellular state changes in response to BRAF/MEK inhibition in patients with myeloma and cell lines. Transcriptional adaptation preceded detectable outgrowth of genetically discernible drug-resistant clones and was associated with widespread enhancer remodeling. As a dominant vulnerability, dependency on oxidative phosphorylation (OxPhos) was induced. In treated individuals, OxPhos was activated at the time of relapse and showed inverse correlation to MAPK activation. Metabolic flux analysis confirmed OxPhos as a preferential energetic resource of drug-persistent myeloma cells.

CONCLUSIONS

This study demonstrates that cancer cells have the ability to rapidly adapt to precision treatments through transcriptional state changes, epigenetic adaptation, and metabolic rewiring, thus facilitating the development of refractory disease while simultaneously exposing novel vulnerabilities.

Pituitary Imaging Abnormalities and Related Endocrine Disorders in Erdheim-Chester Disease

Simple Summary

Erdheim–Chester disease (ECD) is a rare histiocytic neoplasm that is frequently associated with hypothalamic–pituitary gland involvement leading to endocrine dysfunctions. Frequently, endocrinopathy is permanent and precedes the diagnosis of ECD and may also develop during the course of treatment. However, the exact nature and frequency of hypothalamic–pituitary involvement are unknown. We studied a natural history cohort of 61 subjects with Erdheim–Chester disease and found abnormal pituitary imaging in 47.5% of cases, associated with panhypopituitarism, diabetes insipidus, and a higher median number of pituitary endocrinopathies. These data confirm and significantly extend previous reports of centrally occurring endocrine dysfunction and highlight the need for routine imaging and systematic assessment of hypothalamic–pituitary endocrine function in patients with ECD.

Abstract

Purpose: We examined abnormal pituitary imaging (API) and associated endocrine dysfunction in subjects with ECD. Methods: A cross-sectional descriptive examination of a natural history cohort study diagnosed with ECD was conducted at a clinical research center. Subjects underwent baseline endocrine tests of anterior and posterior pituitary function and dedicated pituitary gland MRI scans. We determined the frequency of various pituitary imaging abnormalities in ECD and assessed its relationships with age, sex, body mass index (BMI), BRAF V600E status, high sensitivity C-reactive protein (hsCRP), erythrocyte sedimentation rate (ESR), pituitary hormone deficits and number, diabetes insipidus (DI), and panhypopituitarism. Results: Our cohort included 61 subjects with ECD [age (SD): 54.3 (10.9) y, 46 males/15 females]. API was present in 47.5% (29/61) of ECD subjects. Loss of the posterior pituitary bright spot (36.1%) followed by thickened pituitary stalk (24.6%), abnormal enhancement (18.0%), and pituitary atrophy (14.8%) were the most common abnormalities. DI and panhypopituitarism were more frequent in subjects with API without differences in age, sex distribution, hsCRP, ESR, and BRAF V600E status compared to normal pituitary imaging. Conclusions: We noted a high burden of API and endocrinopathies in ECD. API was highly associated with the presence of panhypopituitarism and DI. Therefore, a thorough assessment of hypothalamic–pituitary integrity should be considered in subjects with ECD.

Vemurafenib provides a rapid and robust clinical response in pediatric Langerhans cell histiocytosis with the BRAF V600E mutation but does not eliminate low-level minimal residual disease per ddPCR using cell-free circulating DNA

BACKGROUND

Langerhans cell histiocytosis (LCH) is a disease that arises from myeloid cells that phenotypically resemble Langerhans cells (LC), which is typically driven by the BRAF V600E mutation. High-risk LCH has a poor prognosis.

PROCEDURE

Fifteen children with BRAF V600E + LCH received vemurafenib between March 2016 and February 2020. The median age at LCH onset was 2 months and the median age at the start of vemurafenib treatment was 22 months. The median disease activity score (DAS) at the start of vemurafenib treatment was 12 points.

RESULTS

The median duration of vemurafenib treatment was 29 months. All patients responded to treatment, with median DAS of 4 points at week 4 and 1 point at 6 months. Two patients died: 1 of hepatic failure after NSAID overdose and 1 of neutropenic sepsis. Cessation of vemurafenib resulted in relapse in 5 patients and was only possible for 1 patient. Serial measurements of BRAF V600E using cell-free circulating DNA revealed that 7 patients had persistently high mutant allele levels.

CONCLUSION

Vemurafenib is effective in children with BRAF V600E + LCH. However, treatment with vemurafenib does not eradicate the disease and its long-term toxicity has not been established.

BRAF-Mutated Erdheim-Chester Disease: Profound Response to Vemurafenib Visualized With Serial Multimodality Imaging

Erdheim-Chester disease (ECD) is an extremely rare and aggressive non-Langerhans histiocytic disorder. ECD typically presents with bone pain in middle-aged adults, although some patients present with multisystem disease involving the skeleton, central nervous system, cardiovascular system, lungs, and other disease sites. The etiology of ECD is currently unknown, but it is thought to be a reactive or neoplastic disorder. Recently, mutation of the BRAF gene has been found in >50% of ECD cases, and this gene has become a therapeutic target for patients with ECD. Vemurafenib, a BRAF inhibitor, has been approved by the FDA for treatment of ECD. This report presents an elderly male patient with an aggressive phenotype of ECD and highlights the utility of multimodality imaging in monitoring the clinical course and disease response to treatment with vemurafenib.

Clinical characteristics and outcomes of Langerhans cell histiocytosis at a single institution in Thailand: a 20-year retrospective study

Background

Langerhans cell histiocytosis (LCH) is a rare disease characterized by the various systems involved and clinical manifestations with a wide range of symptoms.

Objectives

To describe clinical characteristics, imaging, treatment, and outcomes of pediatric LCH at Phramongkutklao Hospital, Bangkok, Thailand.

Methods

We conducted a 20-year retrospective review of the medical records of patients diagnosed with LCH from birth to 21 years old from January 1, 1997, to December 31, 2016.

Results

In all, 14 patients with median age of 2.5 years were studied. Six (43%) patients had single-system (SS) LCH. Five patients (63%) with multisystem (MS) LCH (n = 8. 57%) had risk-organ involvement (RO+). All patients had plain X-ray imaging of their skull with 11 (79%) showing abnormal findings. Tc-99m bone imaging and fluorodeoxyglucose F18 (FDG) positron emission tomography (PET)-computed tomography (CT) demonstrated abnormal findings in 8 (89%) and 4 (29%) patients, respectively. The 5-year event-free survival (EFS) for patients with RO+ MS-LCH was less than that for those without risk-organ involvement (RO-) MS-LCH and SS-LCH (20% vs. 100%, P = 0.005). Hematological dysfunction, hypoalbuminemia, and conjugated hyperbilirubinemia may be worse prognostic factors for RO+ MS-LCH.

Conclusion

FDG-PET-CT might have a greater accuracy to detect LCH disease than conventional plain X-ray and Tc-99m bone imaging. RO+ MS-LCH has been encountered with relapse and poor outcomes. Hematopoietic involvement, hypoalbuminemia, and conjugated hyperbilirubinemia may be worse prognostic factors for RO+ MS-LCH.