18 F-FDG PET/CT in follow-up evaluation in pediatric patients with Langerhans histiocytosis.

PURPOSE: We evaluated the impact of 18 F-FDG PET/CT in identifying sites of active disease and to assess therapeutic follow up in a group of pediatric patients with Langerhans cell histiocytosis (LCH).

METHOD: During 2007-2013, 13 18 F-FDG PET/CT studies were performed for follow-up in 7 patients with a diagnosis of LCH (4 female, 3 male; 1-12 years-old). PET findings were analyzed and correlated with the CT and MRI. Findings were also follow-up by these techniques.

RESULTS: PET was negative in 4 patients (all diagnosed with bone lesions and one with pituitary involvement also). CT findings showed residual morphological bone lesions in all patients, and hypophysis MRI study showed no abnormal signal. PET remained negative at 10, 14, 25 and 28 months, and no new lesions on CT and MRI were detected. PET was positive in 3 patients (one with cervical lymphadenopathy and 2 with bone lesions, one also with pituitary involvement not identified by PET). CT findings showed pathological cervical lymphadenopathy (n=1), bone lesions (n=2) and also a pituitary MRI lesion (n=1). In a patient with cervical lymphadenopathy histology demonstrated LCH involvement. In the other 2 patients, PET remained positive with an increase of 18 F-FDG bone uptake at 17 and 19 months.

CONCLUSION: In our preliminar study, 18 F-FDG PET is a useful imaging procedure, along with other diagnostic tools, for identification of active lesions.