PET/CT scans are effective to stage disease and to evaluate response to therapy in LCH. Examples of 18-fluoro-deoxyglucose–PET scans with CT identifying response to therapy. (A) A patient with multifocal bone disease with interval improvement of pelvic lesion and decreased PET avidity. (B) A patient with multifocal lymph node disease (cervical, axillary, inguinal) who initially failed to respond to cytarabine therapy, then had significant response to 2 cycles of clofarabine.