Langerhans cell histiocytosis is a neoplastic disorder caused by proliferation of mutated Langerhans cells. Lungs are involved as an isolated organ (IPLCH) or as a part of multisystem disease (MS-LCH). The high resolution computed tomography(HRCT) plays crucial role in diagnosis. The aim of this study was the evaluation of HRCT findings in PLCH patients, and correlation of them with disease extension.
Material: 129 patients (94 with IPLCH and 35 with MS-PLCH) hospitalized between 2007-2021 with histologically confirmed disease were analysed. 
Results: Cysts (89%), nodules (73%), interface sign (32%), emphysema (31%), reticular lesions (22%), cavitary nodules (21%), hilar and mediastinal lymphadenopathy (16%), ground glass opacities (11%), dilatation of the pulmonary artery trunk (9%), bronchiectasis (7%) and honeycomb lesions (1%) were visualized on chest CT. Involvement of the supra-diaphragmatic parts of the lungs was observed in 26% of patients.
Negative correlation was found between the severity of cysts and nodules (R=-0.319; p=0.0002). Also, significant correlation appeared between the presence of the interface sign and the average severity of cysts (17 ± 3.9 vs. 9.5 ± 6.4; p=0.00). Male PLCH patients compared to females were characterized by a higher prevalence of emphysema (44% vs.19%; p= 0.002) and cysts (13.3 ± 6.4 vs. 10.6 ± 6.7; p=0.022). In multivariable analysis factors such as high intensity of cigarette smoking and low severity of cysts with a probability of 79.5%, classified patient as IPLCH.
Conclusion:The high intensity of cigarette smoking and low severity of cysts lesions can be a predictor of isolated PLCH.