Objective To investigate the value of ultrasound in the differential diagnosis of craniofacial Langerhans cell histiocytosis (LCH) and bone involvement of lymphoma in children.MethodsTotally 30 patients with craniofacial LCH and 46 patients with lymphoma confirmed by pathology in Beijing Children"s Hospital from January 2016 to December 2022 were consecutively selected.The difference between the two groups of sonographic characteristics (single/multiple lesions, maximum diameter, internalSliquefaction, blood flow and bone damage, osseous hyper echogenicity, adjacent lymph nodes) of bone destruction was compared.Multivariate diagnosis model was established by binary Logistic regression analysis. The self-sampling method (Bootstrap) was used to verify the differentiation within the system, and the calibration curve was drawn to improve the calibration evaluation.Results The difference of “single/multiple lesions” ,“bone damage”, “ osseous hyper echogenicity ”was statistically significant(P=0.019,＜0.001,＜0.001),and the corresponding identification efficiency was expressed by area under the curve (AUC) as 0.637, 0.728, 0.846；The combined diagnosis model could be effectively established by incorporating the above factors, and the AUC of this model could be significantly increased to 0.940, which was better than that of single factor identification (P < 0.0001, < 0.0001, 0.0041).Internal validation results indicated that the diagnostic model has stable differentiation (AUC:0.927) and good calibration.ConclusionsUltrasound can help to distinguish craniofacial bone destruction caused by LCH and lymphoma. The combined diagnostic model can further improve the diagnostic value of ultrasound and has better clinical promotion prospects.