Langerhans cell histiocytosis in adults is associated with a high prevalence of hematologic and solid malignancies

Pulmonary Langerhans Cell Histiocytosis Post-Hodgkin Lymphoma Completely Resolved With Vinblastine in a Heavy Smoker: Coincidence or Causation?

The association among Langerhans cell histiocytosis, hematolymphoid malignancies, and heavy smoking has been addressed in medical literature to identify a possible potential link. Such occurrence can pose diagnostic challenges, as well as important clinical implications for disease progression and treatment approaches. We present pulmonary Langerhans cell histiocytosis instance in a 35-year-old male patient, with a 34-pack-year smoking history and nodular sclerosing Hodgkin lymphoma stage IIB who developed multiple bilateral lung nodules. The patient completed 6 cycles of doxorubicin (Adriamycin), bleomycin, vinblastine, and dacarbazine chemotherapy and radiotherapy 2 years earlier. CT chest scans revealed numerous micronodules scattered randomly throughout the upper and lower left lung lobes. Subsequent wedge resection exhibited cellular proliferation with grooved nuclei, eosinophilic cytoplasm, and surrounding inflammatory components. Immunohistochemical staining showed positive staining for S100 and CD1a confirming a diagnosis of pulmonary Langerhans cell histiocytosis. The patient responded to a 6-week treatment with vinblastine and prednisolone. A subsequent CT scan of the lungs revealed complete resolution after 3 years. This report underscores the importance of identifying pulmonary Langerhans cell histiocytosis in heavy smokers with Hodgkin lymphoma presenting with multiple nodular pulmonary lesions. For patients with Hodgkin lymphoma and a possible genetic predisposition, smoking may contribute to the overt development of pulmonary Langerhans cell histiocytosis. Therefore, smoking cessation and careful follow-up examinations are required. Further research is recommended to elucidate the underlying mechanisms of this intriguing association.

Cutaneous Manifestations of Myeloid Neoplasms Exhibit Broad and Divergent Morphologic and Immunophenotypic Features but Share Ancestral Clonal Mutations With Bone Marrow

In this study, we performed a comprehensive molecular analysis of paired skin and peripheral blood/bone marrow (BM) samples from 17 patients with cutaneous myeloid or cutaneous histiocytic-dendritic neoplasms. The cutaneous manifestations included 10 patients with cutaneous acute myeloid leukemia (c-AML), 2 patients with full or partial Langerhans cell differentiation, 2 patients with blastic plasmacytoid dendritic cell neoplasms (BPDCN), 1 patient with both Langerhans cell differentiation and BPDCN, and 2 patients with full or partial indeterminate dendritic cell differentiation. Seven of the 10 c-AML patients (70%) exhibited concurrent or subsequent marrow involvement by acute myeloid leukemia, with all 7 cases (100%) demonstrating shared clonal mutations in both the skin and BM. However, clonal relatedness was documented in one additional case that never had any BM involvement. Nevertheless, NPM1 mutations were identified in 7 of the 10 (70%) of these c-AML cases while one had KMT2A rearrangement and one showed inv(16). All 3 patients (100%) with Langerhans cell neoplasms, 2 patients with BPDCN (100%), and one of the 2 patients (50%) with other cutaneous dendritic cell neoplasms also demonstrated shared mutations between the skin and concurrent or subsequent myeloid neoplasms. Both BM and c-AML shared identical founding drivers, with a predominance of NPM1, DNMT3A, and translocations associated with monocytic differentiation, with common cutaneous-only mutations involving genes in the signal transduction and epigenetic pathways. Cutaneous histiocytic-dendritic neoplasms shared founding drivers in ASXL1, TET2, and/or SRSF2. However, in the Langerhans cell histiocytosis or histiocytic sarcoma cases, there exist recurrent secondary RAS pathway hits, whereas cutaneous BPDCN cases exhibit copy number or structural variants. These results enrich and broaden our understanding of clonally related cutaneous manifestations of myeloid neoplasms and further illuminate the highly diverse spectrum of morphologic and immunophenotypic features they exhibit.

Long-term outcomes among adults with Langerhans cell histiocytosis

Advances in the treatment of Langerhans cell histiocytosis (LCH) have resulted in a growing survivor population. There is a lack of data on long-term outcomes among adults with LCH. We conducted a retrospective record review of 219 adults (aged ≥18 years) with LCH. Most common presentation was multisystem (34.2%), followed by single-system pulmonary (32%), unifocal (28.3%), and single-system multifocal (5.5%) LCH. Risk organ involvement (the liver, spleen, or bone marrow) was seen in 8.7% of cases, and 40 of 88 (45.5%) tested cases were BRAFV600E. At a median follow-up of 74 months, 5-year progression-free survival (PFS) was 58.3% and estimated median PFS was 83 months. Median overall survival (OS) was not reached; 5- and 10-year OS rates were 88.7% and 74.5%, respectively. Risk organ involvement was associated with worse PFS (hazard ratio [HR], 4.5) and OS (HR, 10.8). BRAFV600E was not associated with risk organ involvement or survival. When compared with matched unaffected US population, individuals with LCH had a significantly higher risk of overall mortality (standardized mortality ratio [SMR], 2.66), specifically among those aged <55 years at diagnosis (SMR, 5.94) and those with multisystem disease (SMR, 4.12). Second cancers occurred in 16.4% cases, including diverse hematologic and solid organ malignancies. LCH-associated deaths constituted 36.1% of deaths and occurred within 5 years of diagnosis. After 5 years, non-LCH causes of death, including second cancers, chronic obstructive pulmonary disease, and cardiovascular diseases, predominated. Our study highlights, to our knowledge, for the first time, that adults with LCH experience early and late mortality from non-LCH causes and the need for development of targeted survivorship programs to improve outcomes.

BRAF V600E is associated with higher incidence of second cancers in adults with Langerhans cell histiocytosis

In this retrospective study, BRAF mutation status did not correlate with disease extent or (event-free) survival in 156 adults with Langerhans cell histiocytosis. BRAFV600E was associated with an increased incidence of second malignancies, often comprising hematological cancers, which may be clonally related.

Adult-onset Langerhans cell histiocytosis of bone: A case series highlighting a rare entity

Langerhans cell histiocytosis (LCH) is a neoplastic disorder derived from LCH precursor cells that can manifest as a single-system disease or a multisystem disorder. While extensively studied in children, LCH has received less attention in adult patients. We aimed to investigate the pathology and clinical course of LCH in adults presenting with a bone lesion. Cases of osseous LCH diagnosed in patients ≥18 in our center were analyzed. Histologic slides were reviewed, and clinical data were collated. Molecular analysis for BRAF mutation was performed in a subset. Twelve osseous LCH cases with classic morphology and CD1a+/S100+ immunophenotype were identified. Tumors occurred in six females and five males with a median age of 34 years (range: 18-77 years) and involved the craniofacial bones (4), pelvis (3), spine (2), appendicular skeleton (2), and rib (1). Radiographically, tumors appeared as ill-defined lytic lesions, often accompanied by cortical erosion and soft tissue extension, with pain being the most common presentation. On staging work-up with available data, two patients had multifocal bone lesions, two had multi-system disease, and four had solitary lesions. Two patients had prior or concurrent neoplasms, and 63 % of patients (5 out of 8) had a history of smoking. BRAF mutational analysis performed in six cases revealed a BRAFV600E mutation in one, negative result in one, and failed in four archived specimens. Our study highlights the importance of performing staging in patients with adult-onset LCH presenting as a bone lesion, as the clinical extent of the disease can vary widely among individuals.

Clinical and prognostic features of Langerhans cell histiocytosis in adults

Langerhans cell histiocytosis (LCH) is a rare disease characterized by clonal expansion of CD1a+ CD207+ myeloid dendritic cells. The features of LCH are mainly described in children and remain poorly defined in adults; therefore, we conducted a nationwide survey to collect clinical data from 148 adult patients with LCH. The median age at diagnosis was 46.5 (range: 20-87) years with male predominance (60.8%). Among the 86 patients with detailed treatment information, 40 (46.5%) had single system LCH, whereas 46 (53.5%) had multisystem LCH. Moreover, 19 patients (22.1%) had an additional malignancy. BRAF V600E in plasma cell-free DNA was associated with a low overall survival (OS) rate and the risk of the pituitary gland and central nervous system involvement. At a median follow-up of 55 months from diagnosis, six patients (7.0%) had died, and the four patients with LCH-related death did not respond to initial chemotherapy. The OS probability at 5 years post-diagnosis was 90.6% (95% confidence interval: 79.8-95.8). Multivariate analysis showed that patients aged ≥60 years at diagnosis had a relatively poor prognosis. The probability of event-free survival at 5 years was 52.1% (95% confidence interval: 36.6-65.5), with 57 patients requiring chemotherapy. In this study, we first revealed the high rate of relapse after chemotherapy and mortality of poor responders in adults as well as children. Therefore, prospective therapeutic studies of adults with LCH using targeted therapies are needed to improve outcomes in adults with LCH.

A Case of a Coexisting Carcinosarcoma Ex Pleomorphic Adenoma With Langerhans Cell Histiocytosis in the Parotid Gland

Carcinosarcoma ex pleomorphic adenoma is a rare malignant neoplasm, with most cases reported in the parotid gland. We herein report a case of a 75-year-old male referred to our hospital with a long-standing right parotid lesion that was treated in an outside hospital by a superficial parotidectomy. The patient reported a painful, rapidly enlarging mass following the excision. Histopathological examination showed the proliferation of malignant epithelial and mesenchymal elements with a solid sheet of Langerhans cells admixed with eosinophils. The Langerhans cells were reactive to CD1a and BRAF; hence, a diagnosis of carcinosarcoma ex pleomorphic adenoma with Langerhans cell histiocytosis was given. Complete clinical and radiographic workup showed no other organ involvement. The patient underwent total parotidectomy with adjuvant chemoradiation; however, the tumor progressed and showed lung metastasis. We herein report the first case of a concurrent Langerhans cell histiocytosis with associated carcinosarcoma ex pleomorphic adenoma.

Spectrum of second primary malignancies and cause-specific mortality in pediatric and adult langerhans cell histiocytosis

With the advent of targeted therapeutics in Langerhans cell histiocytosis (LCH), there is a growing survivor population that might be at risk for late mortality from non-LCH causes, including second primary malignancies (SPMs). We undertook a large study using the Surveillance, Epidemiology, and End Results (SEER) database to evaluate the patterns of SPMs and cause-specific mortality among individuals with LCH (2000-2016) from the US. We found an increased risk of SPMs in the cohort (standardized incidence ratio [SIR] 2.07). The pediatric group was at a high risk of developing Hodgkin lymphoma (SIR 60.93) and non-Hodgkin lymphoma (SIR 60.88). People with adult-onset LCH were found to have a high risk of developing miscellaneous malignant cancers (SIR 11.43), which primarily included myelodysplastic syndrome. Adults were also at a high risk of developing carcinoma in-situ of vulva at 2-11 months [SIR 62.72] and B-ALL at 60-119 months [SIR 66.29] after LCH diagnosis. Additionally, 5% and 1% of the patients developed prior or concomitant malignancies with LCH, respectively. The 5 yr overall survival (OS) was 96.6% for pediatric and 88.5% for adult LCH cohorts. Most common cause of death was infections in pediatric and SPMs in adult LCH. Our study highlights that despite advances in treatments, people with LCH have an increased mortality risk from non-LCH causes when compared with the general population, including a high risk of SPMs.

Langerhans Cell Histiocytosis in Children: Literature Review

Relevant information on Langerhans cell histiocytosis development and course in children is presented. The current concepts of disease pathogenesis, principles of its severity evaluation, patients stratification into risk groups, as well as of clinical course features are described. Modern approaches to the disease treatment via targeted therapy are summarized and analyzed. 

Incidental Langerhans cell histiocytosis associated with metastatic neuroendocrine tumor in the adult liver

This is an unusual adult case of a metastatic well-differentiated neuroendocrine tumor with incidentally discovered subtle involvement of Langerhans cell histiocytosis (LCH), a clonal proliferation of Langerhans cells. It is important to recognize that LCH can often co-exist with other malignancies (solid > hematologic).

Incidental Gastric Langerhans Cell Histiocytosis and Synchronous Adenocarcinoma of the Colon: An Interesting Case Report and Literature Review

BACKGROUND/AIM

Langerhans cell histiocytosis (LCH) is an uncommon disorder characterized by an abnormal monoclonal proliferation of pathologic Langerhans cells. The clinical presentation of LCH is very unpredictable, ranging from single-system limited disease to severe multi-organ disease with a high mortality rate. LCH usually affects children and very rarely adults. The most common body parts affected by LCH are the bones, skin, lungs, pituitary glands, and lymph nodes. Gastrointestinal tract involvement by LCH is exceptionally rare, and only a few cases have been reported.

CASE REPORT

We present the case of a 50-year-old woman who was referred to our clinic by her primary care physician for an upper endoscopy and colonoscopy and was diagnosed with H. pylori-related gastritis and a synchronous gastric LCH and primary colonic adenocarcinoma. We describe the histologic characteristics and clinical implications of the LCH diagnosis. A review of the published literature revealed that LCH presenting as a gastric solitary lesion is rare.

CONCLUSION

This case highlights the importance of recognizing this rare condition to ensure proper patient follow-up.

Molecular and oral manifestations of langerhans cell histiocytosis preceding acute myeloid leukemia

Background

Langerhans cell histiocytosis (LCH) is a heterogeneous neoplastic disorder that is rarely seen in patients aged 60 years and older. It is reported that elderly patients with LCH have a higher chance of having malignancies. In the oral cavity, patients with LCH can present with mucosal ulcers and extensive osteolysis, making it difficult for clinicians to make a proper diagnosis.

Case presentation

We reported an 82-year-old Chinese woman with oral symptoms as the first presentation of LCH, and eventually developed acute myeloid leukemia (AML). She suffered diffuse ulcers involving the entire gingival mucosa and the left half hard palate, and had lost several teeth. Genomic DNA sequencing of the cells from LCH revealed multiple mutations in TET2, BRAF, SRSF2, NRAS, MAP2K4 and so on. The patient declined the BRAF^V600E inhibitor (Vemurafenib). Although a dramatic improvement of the oral ulcers was achieved after symptomatic treatment, the patient developed acute myeloid leukemia (AML) and died.

Conclusions

This report presented the diagnostic difficulties of LCH with oral manifestations and highlighted the importance of radiological assessments and laboratory tests. Moreover, many of the mutations detected in our LCH patient are frequently seen in AML, suggesting that AML and LCH cells in this patient share the same origin.

Langerhans cell histiocytosis and associated malignancies: A retrospective analysis of 270 patients

PURPOSE

The frequency of Langerhans cell histiocytosis (LCH) and associated malignancies (AM) is greater than statistically expected. Here, we analyze LCH-AM co-occurrence in both children and adults.

METHODS

Between 1991 and 2015, data were collected by regular questionnaires to members of the Histiocyte Society and searches in PubMed and Abstract Books. Patients were grouped by age at LCH diagnosis (≤ and >18 years), and types and timing of AM occurrence were plotted with respect to the LCH diagnosis. For the statistical analysis, only the first AM were considered.

RESULTS

A total of 285 LCH-AM in 270 patients were identified, 116 (43%) ≤ 18 years, and 154 (57%) >18 years. In childhood LCH-AM pairs, leukemias and myeloproliferative disorders (n = 58; 50.0%) prevailed over solid tumors (n = 43; 37.1%) and lymphoma (n = 15; 12.9%). In adults, solid tumors were reported in 61 patients (39.6%), lymphoma, and leukemias and myeloproliferative disorders in 56 (36.4%) and 37 (24.0%) patients, respectively. In most children, AM followed LCH (n = 69, 59.5%), whereas in adults, LCH and AM occurred concurrently in 69 patients (44.8%). In children, T-lineage acute lymphoblastic leukemia (ALL) and promyelocytic acute myeloid leukemia (AML) and retinoblastoma were over-represented and thyroid carcinoma in adults.

CONCLUSIONS

The largest collection of data on LCH-AM to date clearly indicates inherent relationships between specific types of AM and LCH, which may be due to therapy effects, clonal evolution, and germ-line predisposition, respectively. Prospective thorough genetic analysis is warranted and will hopefully shed light on the association of LCH and second neoplasms.

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

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

Case Report: Opposite Effects of BRAF Inhibition on Closely Related Clonal Myeloid Disorders

Langerhans cell histiocytosis (LCH) commonly co-occurs with additional myeloid malignancies. The introduction of targeted therapies, blocking “driver” mutations (e.g., BRAF V600E), enabled long-term remission in patients with LCH. The effect of BRAF inhibition on the course and the prognosis of co-existing clonal hematopoiesis is poorly understood. We report on a 61-year-old patient with systemic BRAF V600E positive LCH and concomitant BRAF wild-type (wt) clonal cytopenia of unknown significance (CCUS) with unfavorable somatic mutations including loss of function (LOF) of NF1. While manifestations of LCH improved after blocking BRAF by dabrafenib treatment, the BRAF wt CCUS progressed to acute myeloid leukemia (AML). The patient eventually underwent successful allogeneic hematopoietic stem cell transplantation (HSCT). We performed an in-depth analyzes of the clonal relationship of CCUS and the tissue affected by LCH by using next-generation sequencing (NGS). The findings suggest activation of the mitogen-activated protein (MAP) kinase pathway in the CCUS clone due to the presence of the RAS deregulating NF1 mutations and wt BRAF, which is reportedly associated with paradoxical activation of CRAF and hence MEK. Patients with LCH should be carefully screened for potential additional clonal hematological diseases. NGS can help predict outcome of the latter in case of BRAF inhibition. Blocking the MAP kinase pathway further downstream (e.g., by using MEK inhibitors) or allogeneic HSCT may be options for patients at risk.

Multifocal, Multisystem Presentation of Adult-Onset Langerhans Cell Histiocytosis on 18F-Fluorodeoxyglucose Positron-Emission Tomography-Computed Tomography: A Rare Case Report

Langerhans cell histiocytosis (LCH), also known as histiocytosis X, is a rare systemic disorder arising from clonal proliferation of immature CD207-positive (langerin) myeloid dendritic cells (histiocytes) in the skin and visceral organs with a tendency to involve single or multiple organ systems with variable clinical course and prognosis. The incidence of LCH is very less in adult and occurs almost exclusively in children. Genital, perianal, and lung lesions are considered to be rare manifestations of adult LCH. We describe a case of 31-year-old, nonsmoker female who presented in February 2020 with itching and burning sensation in perianal and vulvar regions accompanied with multiple nonhealing ulcers and papillomatous lesions. These lesions gradually increased in size with no response to antibiotics and topical steroids. She was advised positron-emission tomography- computed tomography (PET-CT) scan for further evaluation. After PET-CT scan, her provisional diagnosis of multisystem, multifocal Langerhans cell histiocytosis with high-risk organ involvement was made. Both vulvar and perianal lesions were biopsied which was suggestive of Letterer-Siwe variant of LCH. The prognosis of this variant is very poor even with aggressive chemotherapy and 5-year survival rate of only 50%. Hence, it requires careful consideration during diagnosis and management.

Histiocytic Neoplasms, Version 2.2021, NCCN Clinical Practice Guidelines in Oncology

Histiocytic neoplasms are rare hematologic disorders accounting for less than 1% of cancers of the soft tissue and lymph nodes. Clinical presentation and prognosis of these disorders can be highly variable, leading to challenges for diagnosis and optimal management of these patients. Treatment often consists of systemic therapy, and recent studies support use of targeted therapies for patients with these disorders. Observation ("watch and wait") may be sufficient for select patients with mild disease. These NCCN Guidelines for Histiocytic Neoplasms include recommendations for diagnosis and treatment of adults with the most common histiocytic disorders: Langerhans cell histiocytosis, Erdheim-Chester disease, and Rosai-Dorfman disease.

Long-term Outcomes of Adult Pulmonary Langerhans Cell Histiocytosis: A Prospective Cohort

BACKGROUND

The 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.

METHODS

To address this issue, all newly diagnosed PLCH patients 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 extra-pulmonary involvement in initially isolated PLCH. Survival was estimated using the Kaplan-Meier method.

RESULTS

Two hundred six patients (mean age: 39±13 years, 60% females, 95% current smokers) were prospectively followed for a median duration of 5.1 years (interquartile range [IQR], 3.2 to 7.6). Twelve (6%) patients died. The estimated rate of survival at 10 years was 93% (95% confidence interval [CI], 89-97). The cumulative incidences of CRF and/or PH were less than 5% at both 5 and 10 years, and 58% of these patients died. Twenty-seven malignancies were observed in 23 patients. The estimated standardized incidence ratio of lung carcinoma was 17.0 (95% CI, 7.45-38.7) compared to an age- and sex-matched French population. Eight (5.1%) of the 157 patients with isolated PLCH developed extra-pulmonary involvement.

CONCLUSIONS

The long-term prognosis of PLCH is significantly more favourable than was previously reported. Patients must be closely monitored after diagnosis to detect severe complications early.

Langerhans cell histiocytosis in adults: a retrospective, single-center case series

Langerhans cell histiocytosis is rare in adults, and most of what we know about its diagnosis and treatment comes from pediatric studies. We report clinical findings and results of treatment in a retrospective series of 63 consecutive adult patients (18-76 years old), treated at our pediatric unit from 1990 to 2020 using the same approach as for children. Patients were classified as having single-system disease (SS-LCH) in 41 cases, which was unifocal in 34 of them and multifocal in 7, or multisystem disease (MS-LCH) in 17 and primary pulmonary (pLCH) in 5. Twenty patients also had diabetes insipidus. A "wait and see" strategy was recommended after biopsy/surgery for patients with unifocal SS-LCH. Systemic treatment was proposed for cases of SS-LCH involving "special sites" or with multifocal disease, and in cases of MS-LCH. EFS and OS for the cohort as a whole were 62.2% and 100%, respectively, at 5 years and 52.5% and 97.6% at 10 years. Three patients died due to the damage caused by the multiple therapies administered. The rate of disease reactivation was high (affecting 40% of cases), with several reactivations over the years despite multiple lines of treatment. Though clinical history of LCH may differ between adults and children, in the absence of specific, tailored protocols, clinical approach to adult cases may draw on pediatric experience. Patients with limited disease have a good prognosis without any need for systemic therapy. Potentially greater toxicity in adults of systemic treatments generally used in pediatric setting should be borne in mind.

Mitogen-activating protein kinase pathway alterations in Langerhans cell histiocytosis

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

Concomitant Langerhans cell histiocytosis of cervical lymph nodes in adult patients with papillary thyroid carcinoma: A report of two cases and review of the literature

Objective

: Langerhans cell histiocytosis (LCH) is an uncommon entity of unknown etiology. It contains a wide range of clinical presentations. The discovery of oncogenic BRAF V600E mutation in LCH has provided additional evidence that LCH is a neoplasm. Papillary thyroid carcinoma is the most common cancer of the thyroid characterized by a high incidence of BRAF V600E mutations. LCH with concomitant PTC is rare, with few cases reported in the literature.

Cases summary

We identified two cases of LCH with concomitant papillary thyroid carcinoma in adult patients. The first was a 49-year-old female with a thyroid nodule diagnosed with papillary thyroid carcinoma. Later, the patient had a left neck mass; Ultrasound-guided lymph node FNA was diagnosed with Langerhans histiocytosis. Subsequently, a chest CT scan revealed signs of Langerhans cell histiocytosis in the lung. The second case refers to a 69-year-old male who presented with a left thyroid nodule diagnosed on FNA cytology as papillary thyroid carcinoma. The patient was found to have multiple bone lytic lesions. Biopsies revealed Langerhans cell histiocytosis. Later, the patient experienced LCH involvement of the bone marrow with associated secondary myelofibrosis.

Conclusions

LCH is rare in adults; the association with papillary thyroid carcinoma is reported and should be considered in the presence of Langerhans cell groups along with PTC, whether in the thyroid gland or cervical lymph nodes. Once LCH has been diagnosed, pulmonary involvement should also be investigated. This will direct treatment plans for patients with pulmonary or systemic disease involvement.

NRAS Mutations May Be Involved in the Pathogenesis of Cutaneous Rosai Dorfman Disease: A Pilot Study

Background: Purely cutaneous Rosai-Dorfman disease (RDD) is a rare histiocytic proliferative disorder limited to the skin. To date, its pathogenesis remains unclear. Owing to recent findings of specific mutations in the mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) pathway in histiocytic proliferative disorders, it provides a novel perspective on the pathomechanism of cutaneous RDD. We aim to investigate the genomic mutations in MAPK/ERK pathway in cutaneous RDD. Methods: We retrospectively recruited all cases of cutaneous RDD from two hospitals in Taiwan from January 2010 to March 2020 with the clinicopathologic features, immunohistochemistry, and treatment. Mutations of neuroblastoma RAS viral oncogene homolog (NRAS), Kirsten rat sarcoma 2 viral oncogene homolog (KRAS), and v-raf murine sarcoma viral oncogene homolog B1 (BRAF) in MAPK/ERK pathway were investigated by the highly sensitive polymerase chain reaction with Sanger sequencing. Results: Seven patients with cutaneous RDD were recruited with nine biopsy specimens. The median age was 46 years (range: 17–62 years). Four of seven patients (57.1%) received tumor excision, while the other three chose oral and/or topical or intralesional steroids. NRAS mutation was detected in 4 of 7 cases (4/7; 51.7%), and NRAS A146T was the most common mutant point (n = 4/7), followed by NRAS G13S (n = 2/7). There is no KRAS or BRAF mutation detected. Conclusions: We report the NRAS mutation is common in cutaneous RDD, and NRAS A146T was the most frequent mutation in this cohort. Mutations in the NRAS gene can activate the RAS/MAPK signaling and have been reported to be associated with various cancers. It indicates that NRAS mutation in MAPK/ERK pathway may involve the pathogenesis of cutaneous RDD.

Concomitant Langerhans cell histiocytosis of cervical lymph nodes in adult patients with papillary thyroid carcinoma: A report of two cases and review of the literature

Objective

: Langerhans cell histiocytosis (LCH) is an uncommon entity of unknown etiology. It contains a wide range of clinical presentations. The discovery of oncogenic BRAF V600E mutation in LCH has provided additional evidence that LCH is a neoplasm. Papillary thyroid carcinoma is the most common cancer of the thyroid characterized by a high incidence of BRAF V600E mutations. LCH with concomitant PTC is rare, with few cases reported in the literature.

Cases summary

We identified two cases of LCH with concomitant papillary thyroid carcinoma in adult patients. The first was a 49-year-old female with a thyroid nodule diagnosed with papillary thyroid carcinoma. Later, the patient had a left neck mass; Ultrasound-guided lymph node FNA was diagnosed with Langerhans histiocytosis. Subsequently, a chest CT scan revealed signs of Langerhans cell histiocytosis in the lung. The second case refers to a 69-year-old male who presented with a left thyroid nodule diagnosed on FNA cytology as papillary thyroid carcinoma. The patient was found to have multiple bone lytic lesions. Biopsies revealed Langerhans cell histiocytosis. Later, the patient experienced LCH involvement of the bone marrow with associated secondary myelofibrosis.

Conclusions

LCH is rare in adults; the association with papillary thyroid carcinoma is reported and should be considered in the presence of Langerhans cell groups along with PTC, whether in the thyroid gland or cervical lymph nodes. Once LCH has been diagnosed, pulmonary involvement should also be investigated. This will direct treatment plans for patients with pulmonary or systemic disease involvement.

Update on Pulmonary Langerhans Cell Histiocytosis

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

Spectrum of histiocytic neoplasms associated with diverse haematological malignancies bearing the same oncogenic mutation

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.

Cutaneous-group histiocytoses associated with myeloid malignancies: A systematic review of 102 cases

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.

Langerhans cell histiocytosis. Blood. 2020;135:1319-1331. [PMID: 32106306 DOI: 10.1182/blood.2019000934]

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

Regulatory T-cell expansion in oral and maxillofacial Langerhans cell histiocytosis

OBJECTIVE

Langerhans cell histiocytosis (LCH) is a rare myeloid-origin neoplasm characterized by the expansion and dissemination of CD1 a+/CD207+ dendritic cells (LCH cells), but the rarity of its occurrence has long impeded progress in understanding its pathology. We focus on the potentially important role that regulatory T cells (T-reg) play in the oral and maxillofacial LCH tumor microenvironment (TME).

STUDY DESIGN

Nine cases of oral and maxillofacial LCH, diagnosed from 2009 to 2019, were collected retrospectively from the affiliated hospitals of Southern Medical University. Immunohistochemistry was conducted characterizing T cells and T-reg phenotype. Data were evaluated by 1-sample Wilcoxon's test.

RESULTS

Significantly increased frequency and abnormal distributions of T-reg were identified in all the LCH lesion sections. Proliferating T-reg account for a mean average of 11.5% of the total T-cell subsets, with significant difference (Wilcoxon's test; P < .05).

CONCLUSIONS

T-reg expansion in the localized inflammatory TME leads to a failure of immune regulation by suppressing antitumor response, which can be a latent and significant factor contributing to LCH progression. However, T-reg may also acquire the capability for aiding in initiating T-cell responses under the "cytokine storm" at the beginning of LCH onset. T-reg might contribute to the augmentation of tissue repair by transforming growth factor-β (TGF-β), explaining the self-limiting character of LCH.

Childhood Langerhans cell histiocytosis: a disease with many faces

BACKGROUND

Langerhans cell histiocytosis (LCH) is a group of diseases characterized by the proliferation and accumulation of Langerhans cells. Clinical presentations of LCH vary widely.

DATA SOURCES

A PubMed search was conducted using Clinical Queries with the key term "Langerhans cell histiocytosis". The search strategy included meta-analyses, randomized controlled trials, clinical trials, observational studies, and reviews. This paper is based on, but not limited to, the search results.

RESULTS

Generally, patients with LCH can be divided into two groups based on the extent of involvement at diagnosis, namely, single-system LCH and multisystem LCH. The involvement may be unifocal or multifocal. Patients with isolated bone lesions typically present between 5 and 15 years of age, whereas those with multisystem LCH tend to present before 5 years of age. The clinical spectrum is broad, ranging from an asymptomatic isolated skin or bone lesion to a life-threatening multisystem condition. Clinical manifestations include, among others, "punched out" lytic bone lesion, seborrheic dermatitis-like eruption, erythematous/reddish-brown crusted/scaly papules/maculopapules/plaques/patches, and eczematous lesions, diabetes insipidus, hepatosplenomegaly, cytopenias, lymphadenopathy, and an acute fulminant disseminated multisystem condition presenting with fever, skin rash, anemia, thrombocytopenia, lymphadenopathy, and hepatosplenomegaly. The diagnosis is clinicopathologic, based on typical clinical findings and histologic/immunohistochemical examination of a biopsy of lesional tissue. Positive CD1a, S100, and/or CD207 (Langerin) immunohistochemical staining of lesional cells is required for a definitive diagnosis. Watchful waiting is recommended for patients with skin-only LCH. Patients with symptomatic or refractory skin-only LCH may be treated with topical tacrolimus/corticosteroids, topical nitrogen mustard, oral methotrexate, or oral hydroxyurea. The current recommended first-line therapy for patients with multisystem LCH is 12 months therapy with prednisone and vinblastine. Mercaptopurine is added for patients with risk organ involvements.

CONCLUSIONS

Because of the broad spectrum of clinical manifestations and the extreme diversity of disease, LCH remains a diagnostic dilemma. Morphological identification of LCH cells and positive immunochemical staining with CD1a, S100, and/or CD207 (Langerin) of lesional cells are necessary for a definitive diagnosis.

Langerhans cell histiocytosis in adults is associated with a high prevalence of hematologic and solid malignancies

Background

Langerhans cell histiocytosis (LCH) is a rare disorder of histiocyte proliferation. Previous case studies suggest a higher prevalence of hematologic and solid malignancies among LCH patients, possibly due to treatment with tumorigenic agents such as etoposide. We report the first large, single‐institution experience of adult LCH patients with additional malignancies to study the characteristics of these patients.

Methods

We identified 132 consecutive patients >18 years of age with histologically confirmed LCH at our center between 1990 and 2015. Demographics and detailed oncologic history were recorded to identify patients with additional malignancies.

Results

Of 132 adult LCH patients, 42 (32%) patients had an additional malignancy. There were 53 malignancies among the 42 patients, with 31 (58%) preceding LCH diagnosis, 11 concurrent (≤3 months; 21%) with LCH diagnosis, and 11 (21%) after. Median age was 54 years (range 28‐89) with a median follow‐up of 3.7 years (0.1‐22.2) for this cohort. OS at 3 years was 98% in patients with LCH alone and 82% among patients with additional malignancies, with 30 (71%) alive at last follow‐up. Solid tumors, lymphomas, and other hematologic malignancies were observed as follows: 39 (74%), 9 (17%), and 5 (9%).

Conclusion

Our cohort of adult LCH patients demonstrates an unusually high number of additional malignancies. Our study includes predominantly malignancies diagnosed preceding or concurrent with LCH, suggesting a cause of malignancy independent of LCH treatment. Further exploration of the biology of this rare disease may elucidate the mechanism of frequent additional malignancies.