Pb1808: langerhans cell histiocytosis in adolescent patients: a single-center retrospective study

Background: Langerhans cell histiocytosis (LCH) is a myeloid dendritic cell disorder frequently affecting children and adults, however the clinical characteristics and genetic profiles of adolescent LCH remain elusive. Aims: This research focused on the clinical and genetic features of adolescent LCH and aimed to address the knowledge gap. Methods: We performed a single-center retrospective study of 36 adolescent LCH patients aged between 14 and 17 years. Results: At the time of diagnosis, 10 patients were classified as unifocal single system LCH (27.8%), 2 patients had pulmonary single system LCH (5.6%), 5 patients had multifocal single system LCH with bone involvement (13.9%), and 19 patients had multisystem LCH (52.8%). The most prevalent involvement in multisystem patients was pituitary gland (78.9%), followed by the bone (42.1%), lung (42.1%), and lymph nodes (42.1%). Eight (42.1%) patients had risk organ involvement. BRAFN486_P490 was detected in 50% of patients who underwent next generation sequencing. One patient died and thirteen patients relapsed during the follow up. The estimated 5-year OS rate and EFS rate were 94.7% and 59.0%, respectively. Adolescent patients resembled previously reported adult LCH series in organ involvements, prevalent BRAF deletion mutations and clinical outcomes. Summary/Conclusion: As the largest adolescent LCH cohort to date, our study found that the clinical characteristics of adolescent LCH patients may be close to adult LCH.