Langerhans Cell Histiocytosis Research Articles

Clinicopathologic Features of Gastrointestinal Tract Langerhans Cell Histiocytosis

Gastrointestinal (GI) tract involvement by Langerhans cell histiocytosis (LCH) is rare and its clinicopathologic characteristics have only been described in case reports and small series. We reviewed hematoxylin and eosin and CD1a, S100, and Langerin immunohistochemical–stained slides from 47 patients with well-documented demographic and clinical findings. Our cases included 8 children and 39 adults, with a mean follow-up of 63 months. All pediatric patients had concurrent multisystem LCH, presented with GI symptoms, and showed nonpolypoid lesions. Seven (88%) showed multifocal GI disease, including 5 with multiple GI organ involvement. All sampled lesions from children exhibited infiltrative growth. More than half had died of the disease or manifested persistent LCH at last follow-up. Twenty-five of 39 (64%) adults had LCH involving only the GI tract (single system), with the remaining 14 (36%) exhibiting multisystem disease. Adult single-system GI LCH was typically encountered incidentally on screening/surveillance endoscopy (72%). Most exhibited isolated colorectal involvement (88%) as a solitary polyp (92%), with a well-demarcated/noninfiltrative growth pattern (70%), and excellent prognosis (100%). In comparison, adult patients with multisystem LCH more frequently presented with GI symptoms (92%, P < .001), noncolorectal GI site involvement (50%, P = .02), multifocal GI lesions (43%, P = .005), nonpolypoid lesions (71%, P < .001), infiltrative histologic growth pattern (78%, P = .04), and persistent disease (57%, P < .001). Adult patients with multisystem LCH appear to exhibit similar clinicopathologic features to those of pediatric patients. These results demonstrated that adults with single-system LCH involving the GI tract have an excellent prognosis, whereas multisystem LCH occurring at any age carries an unfavorable prognosis. High-risk features of GI LCH include pediatric age, GI symptomatology, noncolorectal GI involvement, multifocal GI disease, nonpolypoid lesions, and infiltrative growth pattern.

Double Trouble: Co-occurrence of Langerhans Cell Histiocytosis and Rosai Dorfman Disease in a Toddler

The coexistence of Rosai-Dorfman disease (RDD) with Langerhans cell histiocytosis (LCH) is very rare, as to date only a handful of cases have been reported. Though both the entities come under the spectrum of histiocytic disorders, the patient outcomes are very different for each one of them. RDD is a benign disorder with often a self-limiting course; whereas LCH has a more aggressive outcome. The pathobiology of this rare co-occurrence is still unknown and the topic of several theories. Case presentation: We report a case of a 2-year-old female patient who presented with fever, pallor, lymphadenopathy and neck pain. X-ray radiograph and Computed Tomography (CT) scan chest showed multiple lytic lesions on vertebra. The biopsy finding of lymph node and bone marrow were consistent with a combined RDD-LCH disease. Conclusion: Combined RDD-LCH presentation is very rare and it’s pathophysiology is still elusive and a topic of numerous conjectures.

Clinical Characteristics and Outcomes in Patients With Localized Gastric Langerhans Cell Histiocytosis: A Case Series

Objectives: Localized gastric Langerhans cell histiocytosis (LCH) characterized by abnormal proliferation of Langerhans cells in the stomach without systemic involvement, is rare; therefore, the clinical characteristics and outcomes of LCH remain unclear. We investigated the clinical characteristics and outcomes in patients diagnosed with localized gastric LCH and have also discussed treatment strategies for this rare disease.Methods: The study included seven patients diagnosed with localized gastric LCH at our hospital between September 1997 and December 2023. We retrospectively reviewed medical records and analyzed the clinicopathological characteristics and patient outcomes.Results: Endoscopically, localized gastric LCH appeared as a small erosion in the distal part of the stomach. Positron emission tomography-computed tomography revealed normal findings in 100.0% (4/4) of patients during pre-treatment workup. Immunohistochemical analysis using S-100 and CD1a showed immunopositive cells in all tested patients. Of the six patients who underwent follow-up, two (33.3%) showed metachronous recurrence at a location distinct from the initial site. However, all patients eventually showed spontaneous regression of the disease, and no gastric LCH-induced mortality was observed during follow-up.Conclusions: Careful and regular surveillance may be sufficient for patients with localized gastric LCH without systemic involvement.

朗格汉斯细胞组织细胞增生症合并噬血细胞综合征1例

朗格汉斯细胞组织细胞增生症合并噬血细胞综合征1例

Concurrent enhancer of Zeste homolog 2 (EZH2) over-expression with BRAFV600E mutation predicts a poor outcome in patients with Langerhans cell histiocytosis (LCH): A pilot study.

e18536 Background: Prior studies demonstrated upregulated EZH2 protein expression and p-ERK1/2 cascade signaling in histiocytic and dendritic cell neoplasms. BRAFV600E is the most common driver mutation reported in LCH patients (34-64%). In melanoma studies, a signaling pathway with BRAFV600E activating mutation resulted in upregulation of EZH2. The frequency of EZH2 co-expression with BRAFV600E is unknown in LCH. Given the limited durable responses after discontinuation of treatment with BRAF inhibitors in histiocytic disorders, we investigated the prognostic role of EZH2 overexpression and BRAFV600E mutation in LCH. Methods: We analyzed a cohort of 27 consecutive patients (pts) diagnosed with LCH at Moffitt Cancer Center and Tampa General Hospital between 2010-2022. Immunohistochemical (IHC) staining using antibodies against EZH2 (D2C9 clone, Cell Signaling) and BRAFV600E (VE1 clone, Ventana medical systems) were performed. Expression was assessed by an IHC score of stain intensity (0, 1+, 2+ and 3+) multiplied by percent positive cells (H score). H score ≥ 30 was considered as positive. Pyrosequencing was performed to detect BRAFV600E mutations and correlated with VE1 staining results. A positive outcome from either IHC or PCR was deemed indicative of mutation positivity, given the robust presence of mutation representation in melanoma studies through IHC. Results: Entire cohort were grouped for pts who had both EZH2 overexpression and BRAFV600E mutation (EZH2/BRAFV600E) versus those who did not. Out of 27 pts, 25.9% (n=7) had both EZH2/BRAFV600E. EZH2/BRAFV600E group differed from control group by age ( p=0.046). BRAFV600E mutation was identified in 37.03% (10) pts, and 40.7% (11) showed expression of VE1 by IHC study. Discrepancies between PCR and IHC study were observed in 4 pts and potentially attributable to the restricted availability of tissue samples. 63% and 48.1% of pts were positive for EZH2 and BRAFV600E respectively. 6 pts were observed, 8 underwent surgery with or without radiation, 12 received induction chemotherapy, and only 1 received a BRAF inhibitor. After 18.6 months of median follow up, 92.6% pts were alive. Overall response rate (ORR) to the 1st line therapy was 55.6%. In univariate analysis of OS, H score and BRAFV600E mutation trended towards worse OS but were not statistically significant owing to small sample size. However, BRAFV600E mutation and EZH2 over expression demonstrated a poor overall survival (OS) ( p=0.012). Conclusions: Our study indicates that concurrent presence of BRAFV600E mutation and EZH2 overexpression correlates with poor OS in LCH pts. We hypothesize that in a subset of LCH pts combination therapy targeting both EZH2 and BRAFV600E may improve ORR or overcome resistance to BRAF inhibitor monotherapy. However, the results of our pilot study need to be validated on a larger sample set.

Phase II study in children and adults under 40 years with newly diagnosed Langerhans cell histiocytosis: protocol for an LCH-19-MSMFB clinical trial in Japan

IntroductionAlthough the prognosis of Langerhans cell histiocytosis (LCH) is excellent, the high recurrence rate and permanent consequences, such as central diabetes insipidus and LCH-associated neurodegenerative diseases, remain to be resolved....

Hematologic malignancies in Li-Fraumeni syndrome.

10613 Background: Li-Fraumeni Syndrome (LFS) is a hereditary cancer predisposition syndrome caused by mutations in the tumor suppressor gene TP53. Since its discovery, a growing list of cancers have been described in association with LFS, predominantly solid tumors. However, hematologic malignancies (HMs) cumulatively account for 4-10% of cancer diagnoses in LFS. In this study, we present the largest series of HMs in families with LFS with detailed clinical courses. Methods: This was a two-center retrospective observational cohort study conducted at the University of Utah and the University of Wisconsin-Madison with IRB approval. Cancer genetics clinic registries were reviewed to identify all families with LFS who also had a confirmed diagnosis of a HM. To meet criteria for LFS, the patient had to have a confirmed germline pathologic or likely pathologic TP53 variant. Patients with a TP53 variant of unknown significance (VUS) were also included if they met classical LFS testing criteria. Data was gathered by manual chart review of both the families’ histories and electronic health records. Results: Among the 121 families identified with LFS, 35 (29%) families had one or more HM. Of these, 17 individuals from 16 families (13%) had confirmed germline TP53 mutations. The most frequent HMs found were acute lymphoblastic leukemia (ALL) (n=6), non-Hodgkin lymphoma (NHL) (n=5), myelodysplastic syndromes (MDS) (n=3), and chronic lymphocytic leukemia (CLL) (n=2). Acute myeloid leukemia (AML), Langerhans cell histiocytosis (LCH), and chronic myeloid leukemia (CML) were each diagnosed once. Most cases were identified in adulthood (n=12, 71%). Of the 19 total HMs, the minority (n=5, 26%) were diagnosed post-cytotoxic therapy and only six (35%) individuals had received a diagnosis of LFS prior to HM diagnosis. The MDS/AML cohort (n=4) all exhibited bi-allelic inactivation of TP53. Two of these four patients achieved long term survival after matched-unrelated donor (MUD) hematopoietic stem cell transplant (HSCT). All three patients who underwent MUD donor HSCT had immune-mediated adverse events. Conclusions: In this study we found a significantly higher incidence of HMs in LFS than previously described, with a predominance of lymphoid over myeloid malignancies. The majority of patients had excellent outcomes after standard of care therapy pointing towards more favorable outcomes for patients with LFS and HMs than previously reported. We also report several unusual immune-mediated adverse events in our patients indicating possible immunogenicity of some TP53 variants. Most patients did not have prior exposure to cytotoxic treatments and were diagnosed with the HM prior to their LFS diagnosis. We also show that 38% of individuals with an HM have multiple family members with an HM, consistent with a familial HM pattern. This underscores the importance of detailed family and personal histories in HM patients found to carry a somatic TP53 variant.

Real-world experience with targeted therapy in patients with histiocytic neoplasms in the Netherlands and in Belgium

AbstractHistiocytic disorders are rare hematologic neoplasms characterized by a notable dependence on mitogen-activated protein kinase signaling. Targeted therapy is an emerging treatment option, yet the number of reported patients remains limited. Here, we describe 40 patients with histiocytic neoplasms who were treated with targeted therapy in 7 tertiary referral hospitals from the Netherlands and Belgium. The cohort comprised of 6 (15%) children and 34 (85%) adults with diverse histiocytoses, including Langerhans cell histiocytosis (LCH; n = 12), Erdheim–Chester disease (n = 14), central nervous system xanthogranuloma (n = 2), Rosai–Dorfman disease (n = 3), histiocytic sarcoma (n = 2), ALK–positive histiocytosis (n = 1), and mixed/unclassifiable histiocytosis (n = 6). Five patients were included in a clinical trial; 35 (88%) received BRAF/MEK inhibitors outside of trials. Among these 35 patients with available follow-up data, median time on targeted treatment was 1.9 years (range, 0.04-5.8 years). Complete or partial responses were observed in 25 of 27 (93%) patients treated for multisystemic and/or solid lesions and 2 of 8 (25%) patients treated for neurodegenerative LCH. Responses were generally durable, although 10 patients lost response after dose reduction or therapy interruption. Responses were recaptured in 9 of 10 cases. Two patients developed new or progressive neurodegenerative lesions: 1 during and 1 after vemurafenib therapy. At last follow-up, 8 adults had stopped targeted therapy because of toxicity. This study corroborates the favorable outcomes of BRAF/MEK inhibition in patients with histiocytosis described previously. However, it also highlights limitations and calls for prospective studies.

Thoracic Frozen Section Pitfalls: Lung Adenocarcinoma Versus Selected Mimics.

Intraoperative (frozen section) analysis of lung lesions (nodules, masses, ground-glass opacities) can occasionally be diagnostically challenging. To describe selected pitfalls in thoracic frozen sections with a focus on the differential diagnosis between adenocarcinoma and its mimics, and to provide tips to prevent misinterpretation. Peer-reviewed literature and the author's experience. A common challenge in thoracic frozen sections is the differential diagnosis between lung adenocarcinoma and its mimics. Diagnostic difficulties arise because mimics of adenocarcinoma often entrap reactive lung epithelium that can appear atypical on frozen section slides. Entities that can be misinterpreted as adenocarcinoma include ciliated muconodular papillary tumor/bronchiolar adenoma, hamartoma, inflammatory myofibroblastic tumor, and pulmonary Langerhans cell histiocytosis. Knowledge of the key clinical, radiologic, and histologic features of these entities can help prevent overdiagnosis of adenocarcinoma. Pathologic findings that facilitate the distinction between adenocarcinoma and its mimics at frozen section include the appearance and contour of the lesion at low magnification, growth patterns, cilia, stromal features, shape of the epithelial cells (cuboidal versus columnar), nuclear features of malignancy (crowding, hyperchromasia, irregular contours), and abruptness of the junction between the lesion and adjacent uninvolved lung. Knowledge of the clinical context, imaging findings, and the surgical consequence of the intraoperative diagnosis can also prevent diagnostic errors. Finally, since adenocarcinomas of the lung are often relatively bland and lack the stromal desmoplasia seen in adenocarcinomas of other organs, familiarity with the morphologic spectrum of lung adenocarcinomas at frozen section analysis is important.

Long-term outcome and prognosis of mixed histiocytosis (Erdheim-Chester disease and Langerhans Cell Histiocytosis)

Erdheim-Chester disease (ECD) is a rare histiocytosis that may overlap with Langerhans Cell Histiocytosis (LCH). This "mixed" entity is poorly characterized. We here investigated the clinical phenotype, outcome, and prognostic factors of a large cohort of patients with mixed ECD-LCH. This retrospective study was performed at two referral centers in France and Italy (Pitié-Salpêtrière Hospital, Paris; Meyer Children's Hospital, Florence). We included children and adults with ECD diagnosed in 2000-2022 who had biopsy-proven LCH, available data on clinical presentation, treatment and outcome, and a minimum follow-up of one year. Outcomes included differences in clinical presentation and survival between mixed ECD-LCH and isolated ECD; we also investigated response to treatments and predictors of survival in the mixed cohort. Survival was analyzed using the Kaplan-Maier method and differences in survival with the long-rank test. Cox regression models were used to evaluate the potential impact of age and gender on survival and to identify predictors of non-response and survival. Out of a cohort of 502 ECD patients, 69 (14%) had mixed ECD-LCH. Compared to isolated ECD, mixed ECD-LCH occurred more frequently in females (51 vs. 26%, p<0.001) and in patients with multisystem disease (≥4 sites). Mixed ECD-LCH more frequently involved long bones (91 vs. 79%, p=0.014), central nervous system (51vs. 34%, p=0.007), facial/orbit (52 vs. 38%, p=0.031), lungs (43 vs. 28%, p=0.009), hypothalamic/pituitary axis (51 vs. 26%, p<0.001), skin (61 vs. 29%, p<0.001), and lymph nodes (15 vs. 7%, p=0.028); the BRAFV600E mutation was also more frequent in mixed ECD-LCH (81 vs. 59%, p<0.001). Targeted treatments (BRAF and/or MEK inhibitors) induced response more frequently than conventional therapies (interferon-α, chemotherapy), either as first-line (77 vs. 29%, p<0.001) or as any line (75 vs. 24%, p<0.001). After a median follow-up of 71 months, 24patients (35%) died. Survival probability was comparable between ECD alone and mixed ECD-LCH (log-rank p=0.948). At multivariable analysis, age at diagnosis (HR 1.052, 95% CI 1.008-1.096), associated hematologic conditions (HR 3.030, 95% CI 1.040-8.827), and treatment failure (HR 9.736, 95% CI 2.919-32.481) were associated with an increased risk of death, while lytic bone lesions with a lower risk (HR 0.116, 95% CI 0.031-0.432). Mixed ECD-LCH is a multisystem disease driven by the BRAFV600E mutation and targeted treatments are effective. Age at diagnosis, bone lesion patterns, associated hematologic conditions, and treatment failure are the main predictors of death in mixed ECD-LCH. None.

Ocular findings in patients with histiocytosis and association with clinical and molecular features

Background/aimsOcular manifestations of histiocytosis and their genetic underpinnings are poorly characterised. This study characterises ocular sites of histiocytosis, notate genetic alterations and correlates to histiocytosis clinical features including subtype and...

Upfront Low-Dose Cytarabine with Prednisolone for Langerhans Cell Histiocytosis with Liver Dysfunction: A Ray of Hope

AbstractThe management of Langerhans cell histiocytosis (LCH) with accompanying liver dysfunction poses significant challenges, and this prompted the development of a modified low-dose cytarabine and prednisolone regimen. In this prospective observational study on children with LCH and liver dysfunction, four patients underwent induction and maintenance chemotherapy. The induction phase included 5 days of 100 mg/m2 cytarabine and 4 weeks of 40 mg/m2 daily prednisolone, with subsequent tapering. Maintenance included a regimen of 5 days of 100 mg/m2 cytarabine, along with oral prednisolone, repeated every 3 weeks. Complete disease resolution occurred after varying chemotherapy cycles. Three patients had liver transplants, and the chemotherapy resumed for 52 weeks after the transplant. In one child, chemotherapy was continued after reaching remission. In conclusion, a modified, less toxic low-dose cytarabine-based chemotherapy effectively managed LCH with liver dysfunction, with liver transplantation as a postremission treatment option.

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.

Mixed histiocytic disorders: Nature versus nurture?

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

Genetic Landscape and Its Prognostic Impact in Children With Langerhans Cell Histiocytosis.

Langerhans cell histiocytosis (LCH) is a rare myeloid neoplasm that predominantly affects young children. To investigate genetic alterations and their correlation with clinical characteristics and prognosis in pediatric LCH. We performed targeted sequencing to detect mutations in LCH lesions from pediatric patients. A total of 30 genomic alterations in 5 genes of the MAPK pathway were identified in 187 of 223 patients (83.9%). BRAF V600E (B-Raf proto-oncogene, serine/threonine kinase) was the most common mutation (51.6%), followed by MAP2K1 (mitogen-activated protein kinase kinase 1) alterations (17.0%) and other BRAF mutations (13.0%). ARAF (A-Raf proto-oncogene, serine/threonine kinase) and KRAS (KRAS proto-oncogene, GTPase) mutations were relatively rare (2.2% and 0.9%, respectively). Additionally, FNBP1 (formin-binding protein 1)::BRAF fusion and MAP3K10 (mitogen-activated protein kinase kinase 10) mutations A17T and R823C were identified in 1 case each, with possible constitutive activation of ERK1/2 phosphorylation. BRAF V600E was more frequent in patients with risk organ involvement, while MAP2K1 mutation was more prevalent in patients with single-system LCH (P = .001). BRAF V600E was associated with craniofacial bone, skin, liver, spleen, and ear involvement (all P < .05). Patients with other BRAF mutations had a higher proportion of spinal column involvement (P = .006). Univariate analysis showed a significant difference in progression-free survival among the 4 molecular subgroups for patients treated with first-line therapy (P = .02). According to multivariate analysis, risk organ involvement was the strongest independent adverse prognostic factor (hazard ratio, 8.854; P < .001); BRAF or MAP2K1 mutation was not an independent prognostic factor. Most pediatric patients with LCH carry somatic mutations involving the MAPK pathway, correlating with clinical characteristics and outcomes for first-line chemotherapy.

Differential Gene Analysis of Langerhans Cell Histiocytosis and the Significance of MMP1-Targeted Drug Repositioning.

Langerhans cell histiocytosis (LCH) is a rare condition predominantly affecting young children. Activation of the MAPK pathway has offered key new insights into the pathogenesis of LCH; however, the precise mechanisms underlying its occurrence and development are still far from being completely elucidated. There is still a relapse/reactivation rate in patients with multisystem LCH. Therefore, this study aimed to investigate other potential LCH pathophysiologies and prospective therapeutic targets. The gene expression omnibus (GEO) database was used to retrieve gene expression profiles of LCH (GSE16395). Three distinct types of analyses were performed after identifying the common differentially expressed genes (DEGs) in LCH: hub gene identification, functional annotation, module construction, drug repositioning, and expression analysis via immunohistochemistry (IHC). We identified 417 common DEGs and 50 central hub genes. This functional study highlighted the significance of keratinization, skin development, and inflammation. In addition, we predicted new drug candidates (RS2 drugs targeting matrix metalloprotease1, MMP1) that could be used for LCH treatment. Finally, gene-miRNA and gene-TF networks and immune cell infiltration were analyzed for MMP1-related genes. MMP1 expression levels in LCH tissues were validated by IHC. Our study identified the central communal genes and novel drug candidates. These shared pathways and hub genes offer new perspectives on future mechanisms of action and therapeutic targets.

A rare case of multisystemic Langerhans cell histiocytosis in an adult affecting the thyroid gland, skeletal system, and pituitary gland: A case report.

Langerhans cell histiocytosis (LCH) is a rare disorder affecting usually children and rarely adults. The most common site affected is bone. The involvement of the thyroid gland in LCH is extremely rare and it is usually observed in an adult as a multisystemic disease. Adult males presented with anterior neck swelling, and fine needle aspiration cytology (FNAC) diagnosed it as suspicious for malignancy. On frozen sectioning, differential diagnosis was given as non-Hodgkin lymphoma and poorly differentiated malignancy. On immunohistochemistry (IHC), tumor cells were positive for CD1a and S100p. Thus, the final diagnosis offered was LCH-thyroid. The pathogenesis is unclear and believed to be related to immune dysfunction, cytokine mediators, viral infection, smoking, and genetic factors. Due to its rarity, thyroid LCH is often misinterpreted as other common disorders of the thyroid and results in delayed diagnosis. This case highlights the importance of histomorphology and the use of ancillary techniques such as IHC to arrive at a diagnosis in time and hence the treatment.

Clinical features and treatment outcomes of liver involvement in paediatric Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is the most common histiocytic disorder in children, and liver involvement in LCH is rare. This retrospective study reported the clinical features and prognosis of patients with hepatic LCH. Liver involvement was defined by histopathological findings, liver dysfunction or abnormalities, or ultrasound imaging. A total of 130 patients (14.5%) with hepatic LCH out of 899 in the LCH population were enrolled. Patients with liver involvement had greater frequencies of skin, lung, hearing system, and haematologic system involvement, and hemophagocytic lymphohistiocytosis (P<0.001, 0.001, 0.002, 0.009, and <0.001, respectively). Overall survival and progression-free survival were lower in LCH patients with liver involvement than in those without liver involvement (P<0.001 and <0.001). In patients with liver involvement, the overall survival (OS) and progression-free survival (PFS) rates were lower in patients with cholangitis than in those without cholangitis (P<0.020 and 0.030). For the treatment response, the response rate of hepatic LCH patients to initial first-line therapy (n=89) was 22.5%. However, there was no significant difference in the response rate or recurrence rate between patients who shifted from first-line treatment to second-line treatment (n=29) or to targeted therapy (n=13) (P=0.453 and 1.000). The response rate of hepatic LCH patients who received initial second-line therapy (n=13) was 38.5%. Two of these patients subsequently experienced bone recurrence. The response rate of hepatic LCH patients who received initial targeted therapy (n=16) was 75.0%. Three patients subsequently experienced recurrence, including 2 in the bone and 1 in the liver and skin. A total of 39.3% of patients who received second-line treatment had severe myelosuppression (grade III-IV), and 50.8% had varying degrees of gastrointestinal events, whereas there was no severe toxicity in patients who received first-line treatment and targeted therapy. Four patients underwent liver transplantation because of liver cirrhosis. The patients’ liver disease improved within a follow-up period of 18-79 months. This study demonstrated that LCH with liver involvement, especially cholangitis, indicates a poor prognosis. Targeted therapy provides a good treatment response and less toxicity. However, it may relapse after withdrawal. Liver transplantation is still a reliable salvage option for patients with end-stage liver disease.

A Report of Pediatric Langerhans Cell Histiocytosis in a Hospital-Based Study

Background: The reports of Iranian Pediatric Langerhans Cell Histiocytosis (LCH) are rare and there is no specific survival rate for those cases. Objectives: This study was designed as a hospital-based project for evaluating the epidemiological data and survival rates of the mentioned patients. Methods: This was a cross-sectional descriptive study that enrolled patients younger than 15 years old with approved LCH malignancy. Data was gathered based on a unique questionnaire and analyzed by SPSS Software version 25. Results: There were 32 cases (male/female ratio = 0.88) who were categorized as high risk (n = 18), moderate (n = 9) and low risk (n = 5), respectively. The mean age of patients was 5.1 years and the common chief complaint in them was bone pain, with the skeleton site of involvement. The 5-years overall and event-free survival rates were 93.3% and 72.9%, respectively. Conclusions: The suggestion is to provide a national registry for pediatric LCH followed by designing future projects around affective genes on the treatment response of the mentioned patients. In that way, we can improve the survival rate of these patients and decrease mortality.

Rare yet Critical Manifestations: A Case of Langerhans Cell Histiocytosis in a Child Presenting with Belt-Like Dorsalgia: Diagnostic and Therapeutic Approach

Langerhans cell histiocytosis (LCH) is a rare disease characterized by abnormal proliferation of Langerhans cells. We present the case of a 9-year-old girl complaining of recent belt-like dorsalgia, whose imaging revealed dorso-lumbar scoliosis and a tumor mass at the posterior arch of T11 with posterior epidural infiltration. Surgical decompression and tumor resection were performed, histopathologically confirming the diagnosis of LCH. This abstract highlight the diagnostic and therapeutic challenges of LCH, emphasizing the importance of a multidisciplinary approach for effective management of this rare disease. Additionally, it underscores the relevance of early intervention and meticulous follow-up to ensure optimal outcomes for patients with LCH.