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PURPOSE Ophthalmic histiocytic lesions comprise a heterogeneous rare group of disorders that are characterized by an abnormal proliferation of histiocytes and may affect all age groups of both sexes. The aim of this study was to highlight the basic demographic, clinical, and histopathological characteristics of this rare group of diseases in ophthalmic practice, which has not been previously studied in this area. Only individual cases have been previously reported. METHODS This was a retrospective study of all biopsied ocular and periocular histiocytic lesions from two centers, King Khaled Eye Specialist Hospital (KKESH) and King Abdulaziz University Hospital (KAUH) in Riyadh, Saudi Arabia, from January 1993 to December 2018. The histopathological diagnosis was confirmed, and the cases were re-classified by reviewing all histopathological slides. The corresponding demographic and clinical data were analyzed. A relevant literature review was also carried out for comparison of our collected analyzed data to published data and to draw our own conclusions. RESULTS A total of 34 ocular/periocular histiocytic lesions in 28 patients who were mostly Saudis (92.9%) were included. The male-to-female ratio was 4:3. The median age at presentation was 6.4 years (range: 2.8-35 years). Twenty-two patients had unilateral involvement, and six patients had bilateral lesions. In patients with Langerhans cell histiocytosis (LCH; L group), the most common presenting findings were eyelid swelling (75%), periocular tenderness (37.5%), proptosis/globe displacement (37.5%) eyelid erythema (25%), and orbital pain (12.5%). In patients with Rosai Dorfman disease (RDD; R group), proptosis/globe displacement occurred in all patients and 80% had decreased vision. Patients in the C group (Cutaneous non-LCH histiocytoses) had variable clinical features because of the different locations of the histiocytic lesions, with the majority involving the eyelids (66.7%). Diagnosis was accurately reached clinically in 38.8%, 33.7%, and 46.7% of patients in the L, C, and R groups, respectively. Overall, the clinical diagnosis was in concordance with the histopathologic diagnosis in 14 out of 34 lesions (41.2%). CONCLUSIONS Histiocytic disease is more likely to be overlooked clinically owing to its rarity. In the C group, juvenile xanthogranuloma (JXG) was the most commonly encountered histiocytic lesion and had a tendency to present at a later age with extremely rare intraocular involvement in contrast to previously published reports. The median age at presentation was higher in group R. All patients in group L had strictly unilateral disease, while RDD (group R) was most commonly bilateral. Future research on genetic aspects, management, and prognosis is necessary.

Adult-onset histiocytoses (AOH), primarily Rosai-Dorfman disease (RDD), Erdheim-Chester Disease (ECD), and adult Langerhans cell histiocytosis (ALCH), are a group of related histiocytic neoplastic disorders featuring multisystemic manifestations. The disorders are largely incurable, and are essentially chronic neoplastic diseases with a variable prognosis. Prompt diagnosis and treatment is important to prevent debilitating and even life-threatening complications. Survivorship issues abound in AOH, due to their multisystemic manifestations and the sometimes recalcitrant chronic inflammation, which can lead to other debilitating complications such as fatigue, weakness, and pain. Because these disorders are rare, few healthcare professionals are proficient in their management; therefore the aim of these guidelines is to offer guidance on how to manage patients, and how to create survivorship care plans through the efforts of an interdisciplinary team.

Aims Histiocytoses are a heterogeneous group of localized or disseminated diseases. Clinical presentation and patients' outcome vary greatly, ranging from mild to life-threatening disorders. Rare cases of systemic or localized histiocytosis harboring ALK rearrangement have been reported. Methods Two cases of CNS histiocytosis were thoroughly investigated by implementing multiple molecular tests, i.e. FISH, RT-qPCR, NGS analysis. Results In a 10-month old girl (patient #1), MRI showed two left hemispheric lesions and a right fronto-mesial lesion histologically consisting of a moderately cellular infiltrative proliferation, composed by CD68(PGM1)+/CD163+ spindle cells. ALK 5'/3'-imbalance and a KIF5B(exon 24)-ALK(exon 20) fusion were documented by RT-qPCR and NGS analysis, respectively. A subsequent CT scan showed multiple hepatic and pulmonary lesions. The patient was started on chemotherapy (vinblastine) associated to an ALK-inhibitor (Alectinib) with remarkable response. In a 11-year-old girl (patient #2), MRI showed a right frontal 1.5 cm lesion. Neuropathological examination revealed a histiocytic proliferation composed by medium sized CD68(PGM1)+/HLA-DR+ cells, showing moderate ALK1 positivity. ALK rearrangement and a KIF5B(exon 24)-ALK(exon 20) fusion were demonstrated also in this case. Subsequent CT, 18F-FDG-PET and MRI scans showed the presence of a single right femoral lesion, proved to be a fibrous cortical defect. Conclusions In ALK-histiocytoses, CNS involvement may occur as part of a systemic disease or, rarely, as its only primary disease localization, which could remain otherwise asymptomatic. The diagnosis often relies on neuropathological examination of brain biopsy, which may pose a diagnostic challenge due to the variable histopathological features. An integrated histological and molecular approach in such cases is recommended.

Background Histiocytic and dendritic cell neoplasms are a diverse group of tumors arising from monocytic or dendritic cell lineage. Whereas the genomic features for Langerhans cell histiocytosis and Erdheim‐Chester disease have been well described, other less common and often aggressive tumors in this broad category remain poorly characterized, and comparison studies across the World Health Organization diagnostic categories are lacking. Methods Tumor samples from a total of 102 patient cases within four major subtypes of malignant histiocytic and dendritic cell neoplasms, including 44 follicular dendritic cell sarcomas (FDCSs), 41 histiocytic sarcomas (HSs), 7 interdigitating dendritic cell sarcomas (IDCSs), and 10 Langerhans cell sarcomas (LCSs), underwent hybridization capture with analysis of up to 406 cancer‐related genes. Results Among the entire cohort of 102 patients, CDKN2A mutations were most frequent across subtypes and made up 32% of cases, followed by TP53 mutations (22%). Mitogen‐activated protein kinase (MAPK) pathway mutations were present and enriched among the malignant histiocytosis (M) group (HS, IDCS, and LCS) but absent in FDCS (72% vs. 0%; p, Histiocytic and dendritic cell neoplasms are a diverse group of tumors arising from the monocytic or dendritic cell lineage. This article presents the molecular characteristics of the four major subtypes of malignant histiocytic and dendritic cell neoplasms, focusing on genomic alterations that could represent therapeutic targets.

Histiocytoses are heterogeneous hematopoietic diseases characterized by the accumulation of CD68(+) cells with various admixed inflammatory infiltrates. The identification of the pivotal role of the mitogen-activated protein kinase (MAPK) pathway has opened new avenues of research and therapeutic approaches. We review the neurologic manifestations of 3 histiocytic disorders with frequent involvement of the brain and spine: Langerhans cell histiocytosis (LCH), Erdheim-Chester disease (ECD), and Rosai-Dorfman-Destombes disease (RDD). Central nervous system (CNS) manifestations occur in 10%-25% of LCH cases, with both tumorous or neurodegenerative forms. These subtypes differ by clinical and radiological presentation, pathogenesis, and prognosis. Tumorous or degenerative neurologic involvement occurs in 30%-40% of ECD patients and affects the hypothalamic-pituitary axis, meninges, and brain parenchyma. RDD lesions are typically tumorous with meningeal or parenchymal masses with strong contrast enhancement. Unlike LCH and ECD, neurodegenerative lesions or syndromes have not been described with RDD. Familiarity with principles of evaluation and treatment both shared among and distinct to each of these 3 diseases is critical for effective management. Refractory or disabling neurohistiocytic involvement should prompt the consideration for use of targeted kinase inhibitor therapies.

The non-Langerhans cell histiocytoses (N-LCH) represent a group of rare diseases with different clinical presentations and imaging features to classical LCH. While there is a long list of entities, only few present with musculoskeletal soft tissue and osseous manifestations alongside the more commonly reported systemic findings. Erdheim-Chester disease (ECD) is typically seen in adults as bilateral and symmetrical long bone osteosclerosis. Rosai-Dorfman disease (RDD) is more commonly seen in children and young adults with bone involvement usually being a manifestation of extra-nodal disease. Primary osseous RDD is very rare, with both displaying rather non-specific imaging features of an expansile lucent lesion with or without an extra-osseous component. Juvenile xanthogranuloma (JXG) is a benign disorder typically seen in very young children. The most common imaging manifestation is a dermal or sub-dermal soft tissue mass. This article reviews the musculoskeletal imaging appearances of the commoner N-LCH.

Histiocytoses are a rare group of proliferative disorders with very similar clinical and histological pictures. We present a case report of two variants seen in an eight-month-old female and five-month-old male in a tertiary hospital in southern Nigeria. They both presented with painless neck swellings and fever, leucocytosis, neutrophilia and lymphopenia. Initial histologic examinations of the cervical lymph nodes biopsy posed a diagnostic conundrum. However, Immuno-histochemical analysis done on both sample showed CD1a, positive S100 in keeping with Langerhans cell histiocytosis in the former. While, that of the latter showed strongly positive CD68, positive S-100 in 30% cells in keeping with Sinus histiocytosis with massive lymphadenopathy (SLMH) in the latter. Clinicians should have a high index of suspicion for histiocytosis in children presenting with generalised lymphadenopathy. Also, apart from the routine histology, immunohistochemistry analysis is recommended for all cases

Introduction. — The recently identified role of a BRAF somatic mutation in the pathophysiologyof Langerhans cell histiocytosis (LCH) offers new therapeutic options. Herein we describe thecase of a 10-month-old infant with refractory high-risk LCH successfully treated with vemu-rafenib.Observation. — The patient first presented with cutaneous LCH at the age of 2 months. Thedisease remained undiagnosed until she was 6 months old, when it rapidly evolved to a multisys-temic high-risk and life-threatening disease, refractory to 2 lines of chemotherapy. BRAFV600Emutation was found at skin biopsy, and targeted therapy with vemurafenib was started whenshe was 10 months old. The treatment induced a fast and sustained response, but rapid relapseoccurred after treatment discontinuation, leading to resumption of treatment, once moreresulting in a sustained response.Conclusion. — Our case highlights the first-line role of dermatologists in establishing the diag-nosis of LCH, especially in children, in whom the eruption may be difficult to identify, leading todelayed diagnosis. Targeted therapy with vemurafenib has recently been described in children in this indication and our results support its efficacy, highlighting the need for prolonged treat-ment and raising the question of maintenance therapy, as well as the necessity for large-scaleand long-term studies., info:eu-repo/semantics/published

Juvenile xanthogranulomas (JXGs) are rare, benign lesions that belong to the large group of non-Langerhans cell histiocytoses. JXG presents with 1 or more erythematous or yellowish nodules that are usually located on the head or neck. Most JXG lesions are congenital or appear during the first year of life. Extracutaneous involvement is rare, but the literature traditionally suggests investigating the possibility of ocular compromise. JXG is mainly a clinical diagnosis, but a skin biopsy may sometimes be needed for confirmation. JXGs on the skin are self-limiting and usually do not require treatment. This review describes the clinical and therapeutic aspects of JXG, emphasizing available evidence and the diagnosis of extracutaneous involvement.

Histiocytoses are one of the ultimate diagnostic challenges that every physician face at least once in his/her life. Giving their protean manifestation and differentiated therapeutic needs, histiocytosis requires extensive characterization and multidisciplinary management. Mixed histiocytosis is an emerging group of syndromes defined by the overlap of Langerhans cell histiocytosis and another histiocytic disorder of different type. Despite rare, it may account for up to a fifth of systemic histiocytosis patients in some series. In this work, we comprehensively review for the first time the clinical, radiological, histopathological and molecular features of mixed histiocytosis in children and adults. Moreover, we propose a clinical classification in three groups that differentiate patients with systemic involvement and worse overall survival to other groups with more localized manifestations and indolent behavior, wanting to ease their recognition and treatment. Interestingly we also found that mixed histiocytosis harbor BRAFV600E mutations with a higher frequency comparing to all other histiocytoses, and may therefore benefit of specific inhibitory drugs.

Histiocytoses are a diverse group of rare, clinically heterogeneous disorders characterised by tissue infiltration of histiocytes, which may result in organ dysfunction and failure. Over 100 different subtypes of histiocytoses have been recognised, including rare cases of ALK-positive histiocytosis. We report a case of histiocytosis in a neonate who presented with refractory thrombocytopenia, anaemia, and intermittent neutropenia. Histiocytes were present in both peripheral blood smears and bone marrow; ALK positivity was demonstrated by immunohistochemistry. Given the scarce reports of this condition, the variable organ involvement, and the different approaches to management in the cases described, we seek to expand the literature by providing a report of our patient whose condition improved without chemotherapy. The presence of histiocytes in peripheral blood smears of patients with this condition has not previously been reported, and it underscores the importance of routine careful evaluation of blood smears.

Background: Histiocytoses are unique disorders; their clinical presentations vary from self-healing lesions to life-threatening disseminated disease. Objectives: We aimed to evaluate the different ...

ContextRosai-Dorfman disease is an uncommon histiocytic disorder most frequently presenting as bilateral cervical lymphadenopathy in children and young adults. Extranodal disease occurs in a significant proportion of patients. It has been recently classified as part of the ‘R group’ of histiocytoses by the Histiocyte Society in 2016. Cutaneous Rosai-Dorfman disease is regarded as a separate disease entity that falls into the ‘C group’ of histiocytoses according to this classification system. The pathogenesis was previously poorly understood; however, recent evidence demonstrating clonality in a subset of cases raises the possibility of a neoplastic process. A possible association with IgG4-related disease remains controversial.ObjectivesTo provide a comprehensive review of Rosai-Dorfman disease, including nodal, extranodal and cutaneous forms, with a particular emphasis on new insights into the possible clonal nature of the disease; to discuss the recently revised classification of the histiocytoses by the Histiocyte Society; and to summarise the findings from the literature regarding the controversial association with IgG4-related disease.Data sourcesThis review is based on published peer-reviewed English literature.ConclusionsClassic Rosai-Dorfman disease, which may be sporadic or familial, is considered a separate entity from cutaneous disease, which is reflected in the revised classification of histiocytoses. An increase in IgG4-positive plasma cells may be seen in Rosai-Dorfman disease. This finding in isolation is of limited significance and should be interpreted with caution. Studies investigating the molecular profile of the disease show that in at least a subset of cases the disease is a clonal process. The classification of Rosai-Dorfman disease is therefore likely to change as our understanding of the aetiopathogenesis evolves.

Reticulohistiocytoses (RH) are rare and clinically heterogeneous histiocytic disorders of dermatological interest. Three clinical entities with superimposable histopathological features are currently considered, namely solitary reticulohistiocytoma, diffuse/generalized reticulohistiocytosis and multicentric reticulohistiocytosis. Although in the last decade, RH studies have only minimally progressed, histiocytosis research has advanced considerably: the prognostic and therapeutic importance of the clinical subclassification of histiocytosis patients as well as of the detection of genetic alterations in the genes of the ERK pathway has been highlighted. According to these insights, we previously reported the presence of molecular alteration RH and described a subset of patients with disseminated multisystem involvement lacking arthritis. In the present review, we aim to update and revise the knowledge regarding RH. We first reviewed their histopathological, immunophenotypical and ultrastructural features, discussed their histopathological differential diagnosis with other conditions characterized by infiltrates made of oncocytic or epithelioid cells (with special regard to Destombes-Rosai-Dorfman disease) and finally summarized the molecular landscape of RH. We therefore tried to adjust the clinical subclassification of Langerhans cell histiocytosis to the clinical phenotypes of RH, outlining five clinically different groups of patients. Finally, we reconsidered the clinical workflow to the evaluation of RH patients, in light of the 5 different clinical groups and discussed the different therapeutic approaches and the possible role of target inhibitors.

Erdheim-Chester disease (ECD) is characterized by the infiltration of tissues by foamy CD68+CD1a− histiocytes, with 1500 known cases since 1930. Mutations activating the MAPK pathway are found in more than 80% of patients with ECD, mainly the BRAFV600E activating mutation in 57% to 70% of cases, followed by MAP2K1 in close to 20%. The discovery of BRAF mutations and of other MAP kinase pathway alterations, as well as the co-occurrence of ECD with LCH in 15% of patients with ECD, led to the 2016 revision of the classification of histiocytoses in which LCH and ECD belong to the “L” group. Both conditions are considered inflammatory myeloid neoplasms. Ten percent of ECD cases are associated with myeloproliferative neoplasms and/or myelodysplastic syndromes. Some of the most striking signs of ECD are the long bone involvement (80%-95%), as well as the hairy kidney appearance on computed tomography scan (63%), the coated aorta (40%), and the right atrium pseudo-tumoral infiltration (36%). Central nervous system involvement is a strong prognostic factor and independent predictor of death. Interferon-α seems to be the best initial treatment of ECD. Since 2012, more than 200 patients worldwide with multisystem or refractory ECD have benefitted from highly effective therapy with BRAF and MEK inhibitors. Targeted therapies have an overall, robust, and reproducible efficacy in ECD, with no acquired resistance to date, but their use may be best reserved for the most severe manifestations of the disease, as they may be associated with serious adverse effects and as-yet-unknown long-term consequences.

The non-Langerhans cell histiocytoses (non-LCH) are rare and benign histiocytic disorders. We present a 61-year-old female with progressive skin-colored nodules on the face and extremities. The skin biopsy showed dermal infiltration of foamy histiocytes. Further imaging study showed erosive arthritis and lymphadenopathy. The microscopical feature of anterior mediastinal lymph node was similar to that in the skin. Thus, the diagnosis is non-LCH with joints and lymph nodes involvement. This patient presented both the clinical manifestations of multicentric reticulohistiocytosis (MRH) and histologic findings of xanthoma disseminatum (XD), indicating the plausible association and the shared disease spectrum of MRH and XD.

Background: Histiocytoses are rare diseases affecting mainly children and can occur in any organ of the body. They are divided into Langerhans type and non-Langerhans type. Langerhans cell histiocytosis (LCH) mainly affects skin, bones, and lymph nodes but can also affect the hematopoietic system. Bone lesions can be critical when they involve skull base, orbit, or vertebrae and can cause permanent neurological sequelae or death. Histopathological diagnosis and molecular markers are the mainstay for accurate diagnosis. Sixty percent of LCH cases show mutation in the BRAF oncogene. They are treated with multimodality treatment which includes surgery, chemotherapy, and BRAF inhibitor therapy. Owing to the rarity of the disease and paucity of cases, the understanding and standardization of treatment is still evolving. Case Report: A 14-year-old boy presented with backache, and his imaging showed erosion of first sacral vertebral body with soft tissue component impinging and compressing the spinal canal. Histopathology and molecular diagnosis showed LCH which was positive for BRAF gene mutation. Adequate canal decompression and near-total removal of the disease load with fixation of weight-bearing axis resulted in symptomatic relief and good outcome. Systemic chemotherapy was given for the small residual disease due to fear of recurrence and impending neurological complications. He responded well to first-line therapy with vinblastine and prednisolone with complete resolution of disease on a follow-up scan. Conclusion: Accurate diagnosis with molecular markers is essential for a good outcome of LCH. Treatment of lesions at critical locations like skull base, orbit, or vertebral axis needs to be tailored to prevent permanent neurological deficits. Newer therapies in the form of BRAF inhibitors are on the way, but the efficacy and benefit need to be tested.

Introduction. Non-Langerhans cell histiocytoses (non-LCH) are a group of rare diseases with varied clinical manifestations and overlapping features seen among the subtypes. Here, we present a case of Rosai-Dorfman disease with features of necrobiotic xanthogranuloma. Case. A 45-year-old female presented with a 10-year history of an enlarging neck mass with normal overlying skin accompanied by dysphagia and multiple asymptomatic pink to yellowish-brown papules, nodules, and plaques on the face, trunk and extremities. Biopsies of a skin nodule and plaque revealed granulomatous dermal infiltrates (lymphocytes, foamy histiocytes, and Touton giant cells), emperipolesis and areas of necrosis. CD1A and Fite-Faraco staining showed negative results while CD68 and S100 positively stained the tissues of interest. Histopathology of the neck mass paralleled these findings in addition to being negative for lymphoid markers. Patient had monoclonal gammopathy and thyromegaly with enlarged cervical lymph nodes on further tests and imaging. Intralesional and systemic steroids were given which led to flattening of skin lesions and improvement in dysphagia, respectively. Conclusion. Diagnosis and classification of a particular type of non-LCH may be difficult due to similarities across its subtypes. Hence, it is our belief that these diseases may occur on a spectrum. Treatment involves a multidisciplinary approach for the best possible care.

The histiocytoses are a rare, heterogeneous group of disorders defined by proliferation of histiocytes in numerous organs, including the skin, bone marrow, liver, bone, and/or other organs [1]. Classification systems have evolved over time, and there are now five groups, defined by cell of origin, molecular mutations, and clinical behavior [1]. Langerhans cell histiocytosis (LCH) is the most common disorder in this category, is confirmed with histologic expression of CD1a and CD207, and most commonly affects bone and skin. Non-LCH disorders, of which there are many, and of which may include overlapping pathologic or clinical features, include Erdheim-Chester disease, juvenile xanthogranuloma, Rosai-Dorfman syndrome, malignant histiocytoses, and hemophagocytic lymphohistiocytosis (HLH), among others [1]. Molecular features are increasingly recognized in the histiocytoses: BRAF mutations and MAPK pathway alterations are the most commonly identified mutations in this group of disorders [2]. However, the significant variability in presentation, histology, molecular findings, and clinical behavior make these disorders challenging for the clinician.

Histiocytoses are a group of rare disorders characterized by a proliferation of monocytes/macrophages and dendritic cells. We present a case of a 3-year-old girl with a diffuse papular eruption without systemic symptoms demonstrating a proliferation of strongly CD1a+ histiocytes, but negative for S-100 and langerin on histopathology. Systemic work-up including bone marrow biopsy was unremarkable, and the patient received a diagnosis of CD1a+ S- 100-indeterminate cell histiocytosis.

International audience; Langerhans cell histiocytosis (LCH) is characterized by inflammatory lesions containing abundant CD1a+ CD207+ histiocytes that lead to the destruction of affected tissues. This disease has a remarkable pleiotropic clinical presentation and most commonly affects young children. Although the current mortality rate is very low for childhood LCH patients (

Tumours derived from histiocytes/macrophages and from dendritic cells are extremely rare. They mainly occur in lymphoid tissues, where they account for less than 1% of tumours, but they can be also found in extranodal sites. These neoplasms represent a heterogeneous group of diseases with a variable clinical behavior even within the same tumour entity, ranging from localized and indolent forms to systemic aggressive processes. Diagnosis is based on histological and immunophenotypic features, but overlaps occur across diseases with different biological nature and clinical course, thus correlation with clinical and radiological features is sometimes necessary for final diagnosis. The driver mutations identified during the last few years contributed to a better understanding of the pathogenesis of some of these tumours and in some of them turned out to be useful for diagnosis and treatment.

An extremely rare case of sinus histiocytosis of the non-Langerhans cell histiocytoses type is described in 55-year-old patient with isolated localization of cutanious lesion on the right cheek without involvement of nodular structures. Main skin lesion was an erythematous-cyanotic node with multiple milia-like lesions on the top of it. Histologically revealed feature was a large number of plasma cells, besides phenomenon of emperipolesis was described, which was first falsely perceived by pathologists as phagocytosis. In immu-nohistochemistry assay the changes were characterized by proliferation of large polygonal histiocytes with accumulation of pentalamellar markers in its cytoplasm (protein S-100, CD68).

Necrobiotic xanthogranuloma is a rare chronic condition, belonging to the group C non-Langerhans cell histiocytoses, which is relevant due to the possibility of extracutaneous involvement and association with systemic diseases, particularly hematologic malignancies. The case reported here was only diagnosed after nine years of evolution and was associated with plasma cell dyscrasia. After treatment with cyclophosphamide, dexamethasone, and thalidomide, there was a reduction of cutaneous lesions and serum levels of monoclonal protein.

ObjectivePeritoneal or mesenteric tumours may correspond to several tumour types or tumour-like conditions, some of them being represented by histiocytosis. This rare condition often poses diagnostic difficulties that can lead to important time delay in targeted therapies. Our aim was to describe main features of histiocytoses with mesenteric localisation that can improve the diagnostic process.DesignWe performed a retrospective study on 22 patients, whose peritoneal/mesenteric biopsies were infiltrated by histiocytes.ResultsAbdominal pain was the revealing symptom in 10 cases, and 19 patients underwent surgical biopsies. The diagnosis of histiocytosis was proposed by initial pathologists in 41% of patients. The other initial diagnoses were inflammation (n=7), sclerosing mesenteritis (n=4) and liposarcoma (n=1). The CD163/CD68+CD1a- histiocytes infiltrated subserosa and/or deeper adipose tissues in 16 and 14 cases, respectively. A BRAFV600E mutation was detected within the biopsies in 11 cases, and two others were MAP2K1 mutated. The final diagnosis was histiocytosis in 18 patients, 15 of whom had Erdheim-Chester disease. The median diagnostic delay of histiocytosis was 9 months. Patients treated with BRAF or MEK inhibitors showed a partial response or a stable disease. One patient died soon after surgery, and five died by the progression of the disease.ConclusionDiagnosis of masses arising in the mesentery should be carefully explored as one of the possibilities in histiocytosis. This diagnosis is frequently missed on mesenteric biopsies. Molecular biology for detecting the mutations in BRAF or in genes of the MAP kinase pathway is a critical diagnostic tool.

BackgroundThe long-term outcomes of adult pulmonary Langerhans cell histiocytosis (PLCH), particularly survival, are largely unknown. Two earlier retrospective studies reported a high rate of mortality, which contrasts with our clinical experience.MethodsTo address this issue, all patients with newly diagnosed PLCH referred to the French national reference centre for histiocytoses between 2004 and 2018 were eligible for inclusion. The primary outcome was survival, which was defined as the time from inclusion to lung transplantation or death from any cause. Secondary outcomes included the cumulative incidences of chronic respiratory failure (CRF), pulmonary hypertension (PH), malignant diseases and extrapulmonary involvement in initially isolated PLCH. Survival was estimated using the Kaplan–Meier method.Results206 patients (mean age 39±13 years, 60% female, 95% current smokers) were prospectively followed for a median duration of 5.1 years (IQR 3.2–7.6 years). Of these, 12 patients (6%) died. The estimated rate of survival at 10 years was 93% (95% CI 89–97%). The cumulative incidences of CRF and/or PH were ConclusionThe long-term prognosis of PLCH is significantly more favourable than has previously been reported. Patients must be closely monitored after diagnosis to detect severe complications early.

Activating mutations in the BRAF-MAPK pathway have been reported in histiocytoses, hematological inflammatory neoplasms characterized by multi-organ dissemination of pro-inflammatory myeloid cells. Here, we generate a humanized mouse model of transplantation of human hematopoietic stem and progenitor cells (HSPCs) expressing the activated form of BRAF (BRAFV600E). All mice transplanted with BRAFV600E-expressing HSPCs succumb to bone marrow failure, displaying myeloid-restricted hematopoiesis and multi-organ dissemination of aberrant mononuclear phagocytes. At the basis of this aggressive phenotype, we uncover the engagement of a senescence program, characterized by DNA damage response activation and a senescence-associated secretory phenotype, which affects also non-mutated bystander cells. Mechanistically, we identify TNFα as a key determinant of paracrine senescence and myeloid-restricted hematopoiesis and show that its inhibition dampens inflammation, delays disease onset and rescues hematopoietic defects in bystander cells. Our work establishes that senescence in the human hematopoietic system links oncogene-activation to the systemic inflammation observed in histiocytic neoplasms., BRAF-MAPK activating mutations are reported in histiocytoses—hematological neoplasms with widespread pro-inflammatory myeloid cells. Here, the authors show that an activating mutant BRAF in haematopoietic stem and progenitor cells causes an oncogene-induced senescence response leading to myeloid restricted haematopoiesis, inflammation and histiocytosis.

Progressive nodular histiocytosis (PNH) is a rare condition characterized by progressive eruption of multiple yellowish-brown papules and nodules on the skin and mucous membranes. We present the case of a 37-year-old Caucasian man with gradually increased appearance of nodular lesions on the forehead and right temple. These lesions were initially diagnosed as xanthomas and did not respond to intralesional injections of triamcinolone. Additional biopsy revealed an intense dermal infiltrate of foamy mononuclear epithelioid cells with a minor admixture of plasma cells, lymphocytes, and scattered multinucleated giant cells. On immunohistochemical staining, the lesional cells were positive for CD163 and CD68 and negative for CD1a, thus confirming a mononuclear-macrophage lineage. The clinical presentation and the histological impression lead to the diagnosis of PNH. This condition could be challenging, mimicking microscopically similar lesions of the non-Langerhans cell histiocytosis group. Although uncommon, PNH stands out due to its clinical and microscopic features and should be taken into consideration in the differential diagnosis of cutaneous histiocytoses.

Erdheim-Chester disease (ECD) is a very rare chronic life-threatening systemic disorder with non-specific skin involvement. It was formerly included in the non-Langerhans cell histiocytosis group. However in the recent revised classification of histiocytoses and neoplasms of the macrophage-dendritic cell lineage, ECD is classified in the “Langerhans-related group” due to the showed clonal mutations involving genes of RAS-RAF-MEK-ERK protein kinase pathways detected in more than 80% of the patients similar to Langerhans cell histiocytosis. The heterogenous manifestations of ECD are caused by infiltration of histiocytes on many organs such as skeleton, central nervous system (CNS), cardiovascular system (CVS), lungs, orbit, kidneys, pituitary glands and skin. Although most parts of the cardiovascular system can be affected, pericardium and perivascular parts of the large vessels are most commonly affected. Cardiovascular manifestations are the major cause of mortality in ECD. As there are no specific symptoms of ECD, awareness of its multisystemic involvement and multidisciplinary approach is very important in diagnosis. Although skin findings including xanthelasma-like eyelid lesions and xanthomatous papulonodular lesions are not specific, they may play important role in the early diagnosis of the ECD when co-existing with systemic findings of the disease. Some patients of ECD follow an indolent clinical course and active treatment is necessary for symptomatic disease, CNS involvement or evidence of organ dysfunction. There are many treatment options however all of these, except for IFN-α, have low level of evidence for survival benefit. Vemurafenib is a new therapeutic option targeting the pathogenesis of ECD.

Contains fulltext : 232941.pdf (Publisher’s version ) (Open Access) Histiocytic disorders are a spectrum of rare diseases characterised by the accumulation of macrophage-, dendritic cell-, or monocyte-differentiated cells in various tissues and organs. The discovery of recurrent genetic alterations in many of these histiocytoses has led to their recognition as clonal neoplastic diseases. Moreover, the identification of the same somatic mutation in histiocytic lesions and peripheral blood and/or bone marrow cells from histiocytosis patients has provided evidence for systemic histiocytic neoplasms to originate from haematopoietic stem/progenitor cells (HSPCs). Here, we investigated associations between histiocytic disorders and additional haematological malignancies bearing the same genetic alteration(s) using the nationwide Dutch Pathology Registry. By searching on pathologist-assigned diagnostic terms for the various histiocytic disorders, we identified 4602 patients with a putative histopathological diagnosis of a histiocytic disorder between 1971 and 2019. Histiocytosis-affected tissue samples of 187 patients had been analysed for genetic alterations as part of routine molecular diagnostics, including from nine patients with an additional haematological malignancy. Among these patients, we discovered three cases with different histiocytic neoplasms and additional haematological malignancies bearing identical oncogenic mutations, including one patient with concomitant KRAS p.A59E mutated histiocytic sarcoma and chronic myelomonocytic leukaemia (CMML), one patient with synchronous NRAS p.G12V mutated indeterminate cell histiocytosis and CMML, and one patient with subsequent NRAS p.Q61R mutated Erdheim-Chester disease and acute myeloid leukaemia. These cases support the existence of a common haematopoietic cell-of-origin in at least a proportion of patients with a histiocytic neoplasm and additional haematological malignancy. In addition, they suggest that driver mutations in particular genes (e.g. N/KRAS) may specifically predispose to the development of an additional clonally related haematological malignancy or secondary histiocytic neoplasm. Finally, the putative existence of derailed multipotent HSPCs in these patients emphasises the importance of adequate (bone marrow) staging, molecular analysis and long-term follow-up of all histiocytosis patients.

Background Histiocytoses are haematological disorders of bone marrow origin that share many biological and clinical features with haematological neoplasms. The association between histiocytoses of the cutaneous-group and myeloid malignancies is a poorly investigated topic of high biological and clinical impact. Methods We performed a systematic review of the scientific literature, compliant with PRISMA guidelines, to unravel the clinical and pathological features of this intriguing association. Findings We gathered and analysed 102 patients. Most were children with generalised cutaneous eruptions and displayed risk organ involvement (i.e. bone marrow, spleen, liver). Interestingly, all these features are uncommonly encountered in C-group histiocytosis not associated with haematological neoplasms. Conclusions Our review shows that generalised eruptions and risk organ involvement in cutaneous-group histiocytosis should raise a suspicion for a concomitant myeloid neoplasm both in children and in adults and warrant further investigations. A rapid recognition of this association is required to start a prompt and effective therapeutic management given the aggressive behaviour of the associated myeloid neoplasm in most instances.

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.

Introduction: The long-term outcome of adult pulmonary Langerhans cell histiocytosis (PLCH) is unclear and an association with malignancy is strongly suspected. Aims and Objectives: Our objectives were to determine the overall survival of adult PLCH patients and the incidence of chronic respiratory failure (CRF), pulmonary hypertension (PH), and malignant disorders during follow-up. Methods: All PLCH patients newly diagnosed at adulthood at the French National Reference Centre for Histiocytoses between January 2004 and April 2018 and prospectively registered were included. Results: Two hundred and six patients (39 ± 13 years, 60% females, 95% current smokers) were followed for a median time of 5.1 years; IQR 3.2; 7.6. Twelve patients died during the study. The main cause of death was malignancy (42%, mostly lung cancer). The estimated rates of survival at 5 and 10 years after PLCH diagnosis were 94% (95%CI 90; 98) and 93% (95%CI 89; 97), respectively. The 5 year cumulative incidence of CRF and PH was 6.3% (95%CI 3.4; 10.4) and 5.5% (95%CI 2.8; 9.5), respectively, with no further events after 5 years. Twenty-seven malignancies (11 lung cancer, 41%) were observed in 23 patients, before (n=11), at the time (n=6), or after PLCH diagnosis (n=10, within a median time of 4.1 years; IQR 3.1; 5.0). The incidence of lung cancer was significantly higher than that expected using age- and sex-specific rates from the French population (SIR=16.7, 95%CI 7.3; 38.1). Conclusions: Our findings provide important clues for the management of adult PLCH patients. Further studies are needed to identify risk factors for CRF and clarify the underlying mechanisms of cancer excess in PLCH.