Mixed histiocytic disorders: Nature versus nurture?

Histiocytic diseases arise from MAPK mutations in myeloid progenitors. Depending on whether the progenitor follows a dendritic cell or macrophage/monocyte lineage the final histology results in Langerhans cell histiocytosis, Rosai-Dorfman disease or Erdheim-Chester disease. Commentary on: Friedman et al. Mixed histiocytic neoplasms: A multicentre series revealing diverse somatic mutations and responses to targeted therapy. Br J Haematol 2024;205:127-137.

Selected Case From the Arkadi M. Rywlin International Pathology Slide Seminar: Involvement of Skin and Soft Tissue by Erdheim-Chester Disease.

Erdheim-Chester disease is a rare form of non-Langerhans cell histiocytosis that preferentially involves long bones but can affect a variety of other organs. Initial presentation with extraskeletal involvement is not unusual and is most commonly observed in the central nervous system, heart, retroperitoneum, lungs, and skin. Initial presentation of the disease as a subcutaneous soft tissue mass is exceedingly rare and may pose difficulties for diagnosis. We describe a case of Erdheim-Chester disease that initially presented as a cutaneous and subcutaneous soft tissue mass in the right posterior shoulder of a 52-year-old man.

Erdheim-Chester disease of brain parenchyma without any systemic involvement: A case report and review of literature.

Erdheim-Chester disease is a non-Langerhans cell histiocytosis syndrome characterised by histiocytic infiltration of different organs and systems in the body. Erdheim-Chester disease with isolated central nervous system (CNS) involvement causes diagnostic difficulties due to the absence of systemic findings and may result in misdiagnosis and inaccurate treatment choices. The case discussed in this report exemplifies how challenging it is to diagnose Erdheim-Chester disease with isolated CNS involvement. This case, which presented with progressive pyramidocerebellar syndrome, was clinically and radiologically resistant to all immunosuppressive and immunomodulatory treatments administered. The presence of false negative results in repeated histopathological investigations and the absence of evidence for systemic disease hindered the diagnosis and treatment work-up. In this study, we reviewed and discussed the prominent features of the presented case in light of the relevant literature.

CD68-Negative Histiocytoses with Cardiac Involvement, Associated with COVID-19.

Histiocytoses are rare diseases characterised by infiltration of affected organs by myeloid cells with a monocyte or dendritic cell phenotype. Symptoms can range from self-resolving localised forms to multisystemic lesions requiring specific treatment. To demonstrate extremely rare cases of CD68-negative cardiac histiocytosis with expression of SARS-CoV-2 antigen in infiltrate cells. We demonstrated a case of Erdheim-Chester disease in a 67-year-old man with pericardial involvement and positive dynamics with vemurafenib treatment, an autopsy case of xanthogranulomatous myopericarditis in a 63-year-old man, surgical material of xanthogranulomatous constrictive pericarditis in a 57-year-old man, and an autopsy case of xanthogranulomatosis in a 1-month-old girl. In all cases, xanthogranuloma cells expressed CD163, many of them spike protein SARS-CoV-2, while CD68 expression was detected only in single cells. In this article, we demonstrated four cases of extremely rare CD68-negative cardiac xanthogranulomatosis in three adults and one child with expression of the spike protein SARS-CoV-2 in M2 macrophages. This potential indirect association between COVID-19 and the development of histiocytosis in these patients warrants further investigation. To substantiate this hypothesis, more extensive research is needed.

[Erdheim-Chester disease initially discovered at extraskeletal locations: a clinicopathological analysis of four cases].

Objective: To investigate the clinicopathological features of Erdheim-Chester disease (ECD) initially diagnosed at extraskeletal locations. Methods: Clinical and pathological data of four cases of ECD diagnosed initially in extraskeletal locations were collected at Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, from January 2013 to June 2023. BRAF V600E gene was detected by reverse transcription polymerase chain reaction (RT-PCR). Pertinent literatures were reviewed. Results: Four ECD patients included two males and two females ranging in ages from 2 years 11 months to 69 years. The lesions located in the lung (two cases), central nervous system (one case), and the testicle (one case) were collected in the study. One patient had occasional fever at night, one had nausea and vomiting, and two were asymptomatic. Radiologically, the two pulmonary ECD showed diffuse ground-glass nodules in both lungs, and the lesions in central nervous system and testicle both showed solid masses. Microscopically, there were infiltration of foamy histiocyte-like cells and multinucleated giant cells in a fibrotic background, accompanied by varying amounts of lymphocytes and plasma cells. The infiltration of tumor cells in pulmonary ECD was mainly seen in the subpleural area, interlobular septa, and perivascular and peribronchiolar areas. The fibrosis was more pronounced in the pleura and interlobular septa, and less pronounced in the alveolar septa. Immunohistochemical staining showed that all tumor cells expressed CD68, CD163 and Fô€ƒ¼a; one case showed S-100 expression; three cases were positive for BRAF V600E; all were negative for CD1α and Langerin. RT-PCR in all four cases showed BRAF V600E gene mutation. Conclusions: Extraskeletal ECD is often rare and occult, and could be easily misdiagnosed, requiring biopsy confirmation. The radiologic findings of pulmonary ECD is significantly different from other types of ECD, and the histopathological features of pronounced infiltration in the subpleura area, interlobular septa, perivascular and peribronchiolar areas can be helpful in the differential diagnosis from other pulmonary diseases. Detection of BRAF V600E gene mutation by RT-PCR and its expression by immunohistochemical staining are also helpful in the diagnosis.

Oncogene-induced maladaptive activation of trained immunity in the pathogenesis and treatment of Erdheim-Chester disease.

Trained immunity (TI) is a proinflammatory program induced in monocyte/macrophages upon sensing of specific pathogens and is characterized by immunometabolic and epigenetic changes that enhance cytokine production. Maladaptive activation of TI (ie, in the absence of infection) may result in detrimental inflammation and development of disease; however, the exact role and extent of inappropriate activation of TI in the pathogenesis of human diseases is undetermined. In this study, we uncovered the oncogene-induced, maladaptive induction of TI in the pathogenesis of a human inflammatory myeloid neoplasm (Erdheim-Chester disease, [ECD]), characterized by the BRAFV600E oncogenic mutation in monocyte/macrophages and excess cytokine production. Mechanistically, myeloid cells expressing BRAFV600E exhibit all molecular features of TI: activation of the AKT/mammalian target of rapamycin signaling axis; increased glycolysis, glutaminolysis, and cholesterol synthesis; epigenetic changes on promoters of genes encoding cytokines; and enhanced cytokine production leading to hyperinflammatory responses. In patients with ECD, effective therapeutic strategies combat this maladaptive TI phenotype; in addition, pharmacologic inhibition of immunometabolic changes underlying TI (ie, glycolysis) effectively dampens cytokine production by myeloid cells. This study revealed the deleterious potential of inappropriate activation of TI in the pathogenesis of human inflammatory myeloid neoplasms and the opportunity for inhibition of TI in conditions characterized by maladaptive myeloid-driven inflammation.

PU.1 is a useful nuclear marker to distinguish between histiocytosis and histiocyte-rich tumours.

AIMS: The aim was to test the expression of PU.1 on different types of histiocytoses and to test the utility of PU.1 in confirming or excluding a histiocytic origin in tumour samples with suspicion of histiocytosis. METHODS AND RESULTS: We analysed 66 biopsies of nonmalignant histiocytoses represented by Langerhans-cell histiocytosis (n = 13), Erdheim-Chester disease (ECD) (n = 19), Rosai-Dorfman disease (RDD) (n = 14), mixed ECD-RDD (n = 3), ALK-positive histiocytosis (n = 6), and juvenile xanthogranuloma (n = 11). All cases were positive for PU.1 in reactive and neoplastic histiocytes. In addition, 39 cases of tumours with high-grade cytological atypia were referred to our center as suspicion of malignant histiocytosis/histiocytic sarcoma and only 18 were confirmed. Indeed, more than half of these tumours (21/39) were either undifferentiated malignant tumours with a stroma rich in histiocytes, diffuse large B-cell lymphoma, or high-grade dedifferentiated liposarcoma. PU.1 was useful to distinguish between the negativity of large atypical nuclei and the positivity of stromal reactive histiocytes. CONCLUSION: PU.1 is expressed by all types of histiocytosis. It distinguishes histiocytosis from histiocyte-rich tumours with an easy interpretation due to its sharp nuclear staining. Its negativity in lesional/tumour cells in histiocyte-like lesions is useful to eliminate a histiocytosis.

Erdheim-Chester disease: diffusion-weighted imaging and dynamic contrast-enhanced MRI provide useful information.

This is, to our knowledge, the first case report with in-depth analysis of bone marrow and bone lesions with diffusion-weighted imaging and dynamic contrast-enhanced MRI in Erdheim-Chester disease to date. We present a case of a 70-year-old woman who was referred for an X-ray of the pelvis, right femur and right knee after complaints of migratory arthralgia in hip and knee five months after an initial hip and knee trauma. Bone lesions on X-ray were identified. This case report highlights the strength and complementary use of modern multimodality multiparametric imaging techniques in the clinical radiological manifestations of Erdheim-Chester disease, in the differential diagnosis and in treatment response assessment, which is classically performed using 18FDG PET-CT. Erdheim-Chester disease is a rare form of non-Langerhans' cell histiocytosis, mainly affecting individuals in their fifth-seventh decade of life and without sex predominance. Apart from the typical bilateral symmetric lesions in long bone diaphyseal and metaphyseal regions and classically sparing the epiphyses, this multisystemic disease causes significant morbidity by infiltrating critical organs (the central nervous system, cardiovascular system, retroperitoneum, lungs and skin). With non-traumatic bone pain being the most common complaint, Erdheim-Chester disease is diagnosed most often in an incidental setting on imaging. The imaging workup classically consists of a multimodality approach using conventional radiography, CT, MRI, bone scintigraphy and 18FDG PET-CT. This case report extends this evaluation with diffusion-weighted imaging and dynamic contrast-enhanced imaging techniques.

Ophthalmologic Findings in Pediatric Erdheim-Chester Disease: A Literature Review With a Novel Case Report.

PURPOSE: The authors aim to describe the ophthalmologic manifestations of pediatric Erdheim-Chester disease (ECD). METHODS: The authors describe a novel case of ECD presenting as isolated bilateral proptosis in a child and provide a comprehensive review of the documented pediatric cases to observe overall trends and ophthalmic manifestations of disease. Twenty pediatric cases were identified in the literature. RESULTS: The mean age at presentation was 9.6 years (1.8-17 years) with a mean time of symptom presentation to diagnosis of 1.6 years (0-6 years). Nine patients (45%) had ophthalmic involvement at diagnosis, 4 who presented with ophthalmic complaints: 3 with observable proptosis and 1 with diplopia. Other ophthalmic abnormalities included eyelid findings of a maculopapular rash with central atrophy on the eyelids and bilateral xanthelasmas, neuro-ophthalmologic findings of a right hemifacial palsy accompanied by bilateral optic atrophy and diplopia, and imaging findings of orbital bone and enhancing chiasmal lesions. No intraocular involvement was described, and visual acuity was not reported in most cases. CONCLUSIONS: Ophthalmic involvement occurs in almost half of documented pediatric cases. Typically presenting with other symptoms, the case highlights that isolated exophthalmos may be the only clinical sign, and ECD should be included in the differential diagnosis of bilateral exophthalmos in children. Ophthalmologists may be the first to evaluate these patients, and a high index of suspicion and an understanding of the varied clinical, radiographic, pathologic, and molecular findings are critical for prompt diagnosis and treatment of this unusual disease.

Mimics of Erdheim-Chester disease.

Erdheim-Chester disease (ECD) is a rare histiocytic neoplasm with frequent multiorgan involvement. An accurate diagnosis of ECD requires the correlation of clinical features, histopathologic and radiologic findings. We describe a case series of patients with a referral diagnosis of ECD, whereby the diagnosis was changed to non-histiocytic diseases after comprehensive review at a tertiary care center. This accurate revision of the referral diagnosis of ECD enabled initiation of proper disease-directed therapy in a timely manner for these patients and avoided unnecessary exposure to systemic cytotoxic chemotherapy or targeted agents. Our study highlights the value of a multidisciplinary team of histiocytosis experts in confirming the diagnosis of ECD and also brings attention to other conditions to consider that can mimic ECD, including osteopoikilosis, tenosynovial giant cell tumour, IgG4-related disease, fibrous dysplasia and chronic recurrent multifocal osteomyelitis.

Erdheim-Chester disease: Cytomorphologic clues for a rare histiocytic neoplasm including a distinct tigroid background pattern on smears.

We present the cytomorphologic features of Erdheim-Chester disease (ECD) from 7 patients who have a confirmed diagnosis of ECD, including correlation with the histology on the needle core biopsies. ECD is a rare multi-organ neoplastic histiocytic disorder. The most common locations of involvement are long bones, retroperitoneum, and vasculature. Cytologic preparations often show scant cellularity. Even when neoplastic histiocytes are present on smears, they may be readily overlooked as they are not typically monomorphic, and instead exhibit a variety of morphologies from epithelioid to spindled, with multinucleated giant cells variably present. To our knowledge, ours is the first description of a distinct reticular or tigroid background on smears that is variably present due to rupture of the foamy neoplastic cells. Typically, smears from a targeted mass lesion from any site showing scant polymorphous histiocytes would be regarded as non-diagnostic. A diagnosis of ECD in all cases was based on the needle core biopsy with corresponding immunohistochemical (IHC) stains and BRAF mutational analysis, except for one case in which molecular analysis was not able to be performed. We present these cases to alert practicing cytopathologists to the pitfalls related to the highly variable location, smear cellularity, and cytomorphology of ECD, which should prompt the request of dedicated tissue cores at the time of rapid on-site evaluation and trigger careful clinical-radiologic correlation, as well as consultation with hematopathology colleagues.

[Pelvic mass in 70 years old patient: Difficult diagnosis of Erdheim-Chester disease]. / Masse pelvienne chez un patient de 70 ans : diagnostic difficile de maladie d'Erdheim-Chester.

Erdheim-Chester disease (EC) is a rare disease that is included in Group L in the 2016 revised classification of Langheransian histiocytoses. This disease may be clinically asymptomatic or manifest as a multi-systemic and life-threatening condition. All organs can be affected but typically there is bone involvement, retroperitoneal fibrosis, pituitary involvement, involvement of large vessels, lung, pleura or central nervous system. We are reporting a 70-year-old patient who, as of 2014, had a pelvic mass with retroperitoneal fibrosis and large vessel vasculitis without a definite diagnosis. Histological and molecular examination of the surgical specimen of the pelvic mass with the discovery of the BRAF V600E mutation provided new elements for the definitive diagnosis of Erdheim-Chester disease. We will describe the clinical, histological and molecular features to be known in EC disease.

[Characterization of Endocrine Glands Involved in Erdheim-Chester Disease].

Objective To investigate the clinical and imaging characteristics of endocrine glands involved in Erdheim-Chester disease (ECD).Methods A retrospective analysis was performed on 48 ECD cases pathologically diagnosed from January 2014 to October 2020 in Peking Union Medical College Hospital,including 22 cases of endocrine gland involvement.The clinical,imaging,and pathological characteristics were summarized. Results Pituitary was involved in 17 cases (17/48,35.4%),adrenal gland in 8 cases (8/48,16.7%),and both pituitary and adrenal gland in 3 cases (3/48,6.25%).The most common symptom in patients with pituitary involvement was central diabetes insipidus (13/17,76.5%),and the T1-weighted imaging showed posterior pituitary hypersignal disappearance,pituitary stalk thickening,and abnormally enhanced pituitary nodules.The most common symptom in patients with adrenal gland involvement was adrenal function reduction (3/8,37.5%),and the CT scanning showed diffuse thickening of adrenal glands.BRAF V600E mutation was positive in 13 (13/22,59.1%) cases with ECD involving endocrine glands.Conclusion Pituitary and adrenal glands are the most common sites of ECD involving endocrine glands.A definite diagnosis can be achieved by combining clinical,imaging,and pathological characteristics for timely treatment.

Pulmonary manifestations of Erdheim-Chester disease: clinical characteristics, outcomes and comparison with Langerhans cell histiocytosis.

Erdheim-Chester disease (ECD) is a rare form of non-Langerhans cell histiocytosis that typically affects many organs, including the lung and pleura. However, there are few studies concerning pulmonary involvement in ECD patients, as well as the difference of pulmonary involvement between ECD and Langerhans cell histiocytosis (LCH). We performed a retrospective study of 54 ECD patients, and compared the pulmonary manifestations with those of adult LCH patients in our centre. The median age of diagnosis of the 54 ECD patients was 48 years (range 9-66 years). Chest computed tomography (CT) scans revealed lung involvement in 49 (91%) patients and pleural involvement in 34 (63%). Thirty-three (61%) patients had interstitial lung disease (ILD) with varying degrees of interlobular septal thickening, micronodules, and ground-glass opacities. ECD and LCH patients with pulmonary involvement showed significant differences in smoking status (P < 0·001), respiratory symptoms (P = 0·001) such as cough and pneumothorax (P < 0·001), and radiological findings, including cysts (P < 0·001), opacities (P < 0·001), and pleural thickening (P < 0·001). With a median follow-up duration of 24 months (range, 1-84 months), the estimated three-year overall survival (OS) of this entire ECD cohort was 90·2%. Patients with ILD tended to have worse progression-free survival (PFS) than those with no ILD (P = 0·29).

Challenges in the Histopathologic Diagnosis of Histiocytic Neoplasms.

Histiocytic neoplasms, including Langerhans cell histiocytosis (LCH), Erdheim-Chester disease (ECD), and Rosai-Dorfman disease (RDD), present a diagnostic challenge due to nonspecific fibroinflammatory infiltrates and a diverse clinical presentation. The pathologist can play a key role in classification of these disorders through multidisciplinary collaboration and correlation of pathologic features with clinical and radiologic findings. The histopathologic differential diagnosis is broad, requiring knowledge of the possible diagnoses at each specific anatomic site, and a careful assessment to exclude other inflammatory and neoplastic disorders. An immunohistochemistry panel including CD163, CD1a, langerin, S100, Factor XIIIa, OCT2, and BRAF V600E can provide definitive diagnosis in LCH and RDD, whereas ECD requires classic clinical features as well as confirmation of an activating MAPK pathway mutation by genetic studies.

Intracranial mass lesions and skin discoloration in the armpits as unusual clues to Erdheim-Chester disease: a case report.

BACKGROUND: Erdheim-Chester disease (ECD) is a non-Langerhans histiocytosis that results in multi-organ disease involving the skin, bones, lungs and kidneys. Central nervous system (CNS) involvement occurs in about 50 % of patients, and diabetes insipidus, visual disturbances, and cerebellar ataxia are the most frequent neurological signs. We report a case of Erdheim-Chester disease with central nervous system involvement in the form of enhancing intracranial mass lesions with massive edema. CASE PRESENTATION: The patient presented with vertigo, ataxia, encephalopathy and pyramidal signs. Diagnosis was suggested by xanthomatous skin lesions and a biopsy was compatible with Erdheim-Chester disease demonstrating xanthogranulomas CD68 positive (clone KP1) and CD1a and S100 negative. Testing for BRAF mutation was negative, which precluded treatment with Vemurafenib. Treatment with steroids and interferon resulted in improvement of neurological signs and regression of edema on MRI. CONCLUSIONS: The diagnosis of Erdheim-Chester disease should be considered in intracranial mass lesions. Xanthomatous skin lesions are a clue to the diagnosis.

MAP2K1-driven mixed Langerhans cell histiocytosis, Rosai-Dorfman-Destombes disease and Erdheim-Chester disease, clonally related to acute myeloid leukemia.

Mixed histiocytoses are a rare and recently recognized subset of histiocytic disorders that may involve the skin, characterized by the synchronous or metachronous development of lesions with Langerhans and/or non-Langerhans cell histiocytosis histopathological features. Around 10% of patients diagnosed with histiocytosis may develop a hematological malignancy, often with dramatic prognostic consequences. We hereby describe the exceptional case of a patient developing a MAP2K1-driven mixed histiocytosis with Langerhans cell histiocytosis, Rosai-Dorfman-Destombes disease, and Erdheim-Chester disease features and cutaneous involvement, progressing to a fatal and clonally-related acute myeloid leukemia. We reviewed the literature on similar cases and discussed the histopathological difficulties in their diagnosis and their clinical-pathological features.

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.

Trametinib after disease reactivation under dabrafenib in Erdheim-Chester disease with both BRAF and KRAS mutations.

Major advances have been made in understanding the pathogenesis of Erdheim-Chester disease (ECD) leading to novel treatment strategies. Targeted therapies such as BRAF inhibition have shown a significant impact on disease management, emphasizing the importance of the activated mitogen-associated protein kinase pathway in this disease. However, incomplete responsiveness, potentially limiting adverse effects, and the occurrence of treatment resistance to BRAF inhibition observed in other BRAF-mutant malignancies imply the importance of therapeutic strategies beyond BRAF inhibition. We report a patient with ECD who carried the BRAFV600E mutation and developed treatment resistance under BRAF inhibition despite initial treatment response. Genetic analyses of a newly developing ECD lesion revealed a somatic KRASQ61H mutation without the presence of BRAFV600E Accordingly, the addition of MEK-inhibiting trametinib to BRAF-inhibiting dabrafenib was able to overcome acquired partial treatment resistance. This is the first report of treatment resistance as a result of a secondary MAPK pathway-activating mutation during BRAF inhibition in ECD. This case contributes to the ongoing efforts of simultaneous BRAF/MEK inhibition as a promising strategy in ECD.