Spontaneous regression of langerhans cell histiocytosis in a neonate with multiple bony lesions

Co-existence of BRAF V600E-mutated malignant melanoma and BRAF V600E-mutated Langerhans cell histiocytosis: A case report

Langerhans cell histiocytosis (LCH) is a neoplastic condition of Langerhans cells, and can be associated with other neoplasms, especially BRAF-mutant hematological tumors and papillary thyroid carcinoma. Here we present the first case of co-existing LCH and low cumulative sun damage (low-CSD) melanoma, both of which had a BRAF V600E mutation. A 49-year-old man had a 45 × 43 × 15 mm semi-pedunculated, pigmented tumor in his back but had no other systemic symptoms. Histopathology revealed a 2-mm-sized incidental focus of LCH within a large lesion of low-CSD melanoma. Diffuse immunoexpression of CD1a, langerin/CD207, S100 protein, and BRAF (VE1) was observed in the focus of LCH. Sanger sequencing with microdissection confirmed BRAF V600E mutation in the component of LCH. Interestingly, the advanced melanoma also harbored the same BRAF V600E mutation, although the significance of this tumor combination is still unknown.

Langerhans cell histiocytosis with hemorrhagic uveitis and exudative retinal detachment

Bilateral intraocular involvement in Langerhans cell histiocytosis (LCH) is uncommon. A 15-year-old boy presented with painless decreased vision in right and painful left red eye of 2 weeks duration. Visual acuity was 20/500 and 20/200, respectively. A fixed dilated pupil with exudative retinal detachment was present in the right eye and hemorrhagic iris nodules with hyphema and hypopyon were seen in the left eye. Intraocular pressure was 12 and 31 mmHg, respectively, in each eye. Ocular symptoms were preceded by fever with multiple skin rashes, subcutaneous nodules, and lymph node enlargement. The histopathological examination of skin and lymph node showed histiocytes positive for histiocytic S 100. He was treated with topical steroids and antiglaucoma eye drops along with intravenous vinblastine 6 mg and oral prednisolone (1 mg/kg). Hyphema and hypopyon were resolved, vision improved to 20/320 and 20/80, and intraocular pressure was under control. However, as multisystemic LCH has a poor prognosis, we were unable to save him. Hence, fatal conditions like LCH should also be considered in the differential diagnosis of any hemorrhagic uveitis.

Histiocytoses: emerging neoplasia behind inflammation

Histiocytoses are disorders characterised by inflammation and the accumulation of cells derived from the monocyte and macrophage lineages, which results in tissue damage. Although they are often considered rare disorders with protean clinical manifestations, considerable advances in the understanding of their genetics have led to increased clinical recognition of these conditions, and fuelled further insights into their pathogenesis. In this Review, we describe insights into the cells of origin, molecular pathology, clinical features, and treatment strategies for some of the most common histiocytic disorders, including Langerhans cell histiocytosis, Erdheim-Chester disease, and Rosai-Dorfman disease. With the discovery of recurrent mutations affecting the mitogen-activated protein kinase and mTOR-AKT pathways in some of these histiocytoses, our understanding of these diseases has now evolved from the concept of a primary inflammatory condition to that of a clonal neoplastic disease. This understanding has led to the development of effective mechanism-based therapeutic strategies for patients with histiocytic diseases.

BRAF and MAP2K1 mutations in Langerhans cell histiocytosis: a study of 50 cases

Langerhans cell histiocytosis (LCH) is a proliferation of Langerhans cells, often associated with lymphocytes, eosinophils, macrophages, and giant cells. BRAF mutations, usually V600E, have been reported in 40%-70% of cases, and recently, MAP2K1 mutations have been reported in BRAF-negative cases. We assessed 50 cases of LCH for BRAF mutations and assessed a subset of cases for MAP2K1 mutations. The study group included 28 men and 22 women (median age, 36.5 years; range, 1-78 years). BRAF V600E mutation was detected in 8 (16%) cases including 3 (30%) skin, 2 (11%) bone, 1 (50%) colon, 1 (20%) lung, and 1 (33%) extradural, intracranial mass. MAP2K1 mutations were detected in 6 of 13 (46%) BRAF-negative cases including 2 (100%) lymph node, 2 (50%) bone, 1 (25%) skin, and 1 (100%) orbit. Patients with BRAF mutation were younger than patients with wild-type BRAF (median age, 28 versus 38 years; P = .026). The median age of MAP2K1-mutated patients was 34.5 years, similar to patients without MAP2K1 mutation (41 years; P = .368). In agreement with 2 recent studies, we showed a high frequency of MAP2K1 mutations in BRAF-negative LCH cases. Unlike other studies, the overall frequency of BRAF mutation in this cohort is substantially lower than what has been reported in pediatric patients, perhaps because most patients in this study were adults. Moreover, we showed a high concordance between mutational and immunohistochemical analysis for BRAF mutation. There was no statistically significant association between BRAF or MAP2K1 mutation and anatomic site, unifocal versus multifocal presentation, or clinical outcome.

Langerhans cell histiocytosis: a diagnostic dilemma

Langerhans cell histiocytosis (LCH) is a rare clonal neoplastic disorder of unknown aetiology which can present with a diverse range of clinical presentations. It encompasses a diverse number of idiopathic conditions which can involve multiple body systems and is characterized by bone marrow-derived Langerhans cell proliferation. The disease can affect multiple body systems and lesions can be solitary or widespread. We present a case of a multifocal eosinophilic granuloma (LCH) in a young adult female with clinical signs and symptoms similar to aggressive periodontitis.

CLINICAL RELEVANCE

Langerhans cell histiocytosis is a rare disease which can have a similar clinical presentation to aggressive periodontitis.

IL-17A receptor expression differs between subclasses of Langerhans cell histiocytosis, which might settle the IL-17A controversy

Langerhans cell histiocytosis (LCH) is a lymphoproliferative disorder consisting of abnormal Langerhans cell-like cells and other lymphoid cells. LCH presents as either a multisystem LCH (LCH-MS) or a single-system LCH (LCH-SS). Currently, neither the pathogeneses nor the factors that define these disease subclasses have been elucidated. The interleukin (IL)-17A autocrine LCH model and IL-17A-targeted therapies have been proposed and have engendered much controversy. Those authors showed high serum IL-17A levels in LCH and argued that serum IL-17A-dependent fusion activities in vitro, rather than serum IL-17A levels, correlated with LCH severity (i.e. the IL-17A paradox). In contrast, others could not confirm the IL-17A autocrine model. So began the controversy on IL-17A, which still continues. We approached the IL-17A controversy and the IL-17A paradox from a new perspective in considering the expression levels of IL-17A receptor (IL-17RA). We detected higher levels of IL-17RA protein expression in LCH-MS (n = 10) as compared to LCH-SS (n = 9) (P = 0.041) by immunofluorescence. We reconfirmed these data by re-analyzing GSE16395 mRNA data. We found that serum levels of IL-17A were higher in LCH (n = 38) as compared to controls (n = 20) (P = 0.005) with no significant difference between LCH subclasses. We propose an IL-17A endocrine model and stress that changes in IL-17RA expression levels are important for defining LCH subclasses. We hypothesize that these IL-17RA data could clarify the IL-17A controversy and the IL-17A paradox. As a potential treatment of LCH-MS, we indicate the possibility of an IL-17RA-targeted therapy.

Recent advances in the understanding of Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is a proliferative disease of cells that share phenotypic characteristics with the primary antigen presenting cells of the epidermis. Its clinical manifestations are highly variable, extending from very benign forms to a disseminated, aggressive disease that causes significant mortality. Although many of the fundamental pathogenetic features of LCH have been enigmatic, recent advances have led to a much clearer understanding of the disease. In particular, careful molecular analyses of mouse models and human LCH samples suggest that LCH's cell of origin may not be the epidermal LC itself but a myeloid-derived precursor. Advanced genomic technologies have revealed the presence of activating, somatic BRAF mutations in the majority of patient specimens. Together, these observations have produced a new picture of LCH as a myeloid neoplasm. These advances are likely to have profound implications for the use of targeted therapeutics in LCH.

Recurrent BRAF mutations in Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) has a broad spectrum of clinical behaviors; some cases are self-limited, whereas others involve multiple organs and cause significant mortality. Although Langerhans cells in LCH are clonal, their benign morphology and their lack (to date) of reported recurrent genomic abnormalities have suggested that LCH may not be a neoplasm. Here, using 2 orthogonal technologies for detecting cancer-associated mutations in formalin-fixed, paraffin-embedded material, we identified the oncogenic BRAF V600E mutation in 35 of 61 archived specimens (57%). TP53 and MET mutations were also observed in one sample each. BRAF V600E tended to appear in younger patients but was not associated with disease site or stage. Langerhans cells stained for phospho-mitogen-activated protein kinase kinase (phospho-MEK) and phospho-extracellular signal-regulated kinase (phospho-ERK) regardless of mutation status. High prevalence, recurrent BRAF mutations in LCH indicate that it is a neoplastic disease that may respond to RAF pathway inhibitors.