Characteristic histopathologic and radiographic findings of ECD. (A) PET and (B) ^99mTc imaging demonstrating symmetric diametaphyseal radiotracer uptake in the long bones of the legs (arrows) commonly seen in ECD patients. R indicates the patient's right side. (C) CT and (D) MRI scans revealing sclerotic lesions of the metaphyses of femur and tibia (arrows). (E) Hematoxylin-eosin–stained biopsy section of ECD lesion revealing lipid-laden histiocytes characteristic of ECD. (F) IHC stain for CD68 revealing positivity of histiocytes.