Role of 18 F-FDG PET/CT in the diagnosis and management of patients with Langerhans cell histiocytosis.

Background: Langerhans cell histiocytosis (LCH) is an inflammatory myeloid neoplasm that can involve multisystem organs. Positron emission tomography/computed tomography (PET/CT) has been widely used in tumor staging and efficacy evaluation. However, at present, there are few ¹⁸ F-fluorodeoxyglucose (FDG) PET/CT studies on LCH. This study aimed to explore the possible role of ¹⁸ F-FDG PET/CT in the diagnosis and management of patients with LCH.
Methods: ¹⁸ F-FDG PET/CT images of 22 Chinese patients diagnosed with LCH on biopsy or surgery histopathology between January 2011 and December 2020 were retrospectively analyzed. The incidence of LCH in each system was assessed by a PET/CT scan. The imaging characteristics were analyzed semiquantitatively and qualitatively. The discrepancies between PET/CT and conventional imaging modalities were recorded. Evaluations of curative effect according to RECIST1.1 and PERCIST1.0 were compared using Fisher's exact chi-squared test, and P values <0.05 were considered significant.
Results: Eight (36.4%) of the 22 patients presented with single system involvement (4 isolated site involvement, 4 multiple site involvement), and 14 (63.6%) presented with multiple system involvement. Twenty-one (95.5%) patients had hypermetabolic lesions. Musculoskeletal, lymphatic, respiratory, liver, skin-soft tissue and thyroid involvement were seen in 14 (63.6%), 13 (59.1%), 5 (22.7%), 4 (18.2%), 5 (22.7%) and 1 (4.5%) patient, respectively. Cranial and facial bones were the most common sites of musculoskeletal involvement. Ten patients underwent PET/CT follow-up, and there was no significant difference in curative effect evaluations according to RECIST1.1 and PERCIST1.0. However, among the complete remission cases assessed by RECIST1.1, three were partial metabolic responses assessed by PERCIST1.0, while among the partial response cases assessed by RECIST1.1, one was metabolic progressive disease assessed by PERCIST1.0.
Conclusions: ¹⁸ F-FDG PET/CT is an imaging modality option for the diagnosis and assessment of the curative effect of LCH.
Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-21-823/coif). The authors have no conflicts of interest to declare.
(2022 Quantitative Imaging in Medicine and Surgery. All rights reserved.)