Radiologic findings of adult pelvis and appendicular skeletal Langerhans cell histiocytosis in nine patients.

OBJECTIVE: The purpose of this article was to evaluate the radiologic findings of adult pelvis and appendicular skeletal Langerhans cell histiocytosis (LCH), emphasizing the CT and MR findings. MATERIALS AND METHODS: The images of nine patients with pathologically proven LCH (five men and four women; mean age, 37.11 years) were retrospectively reviewed. Imaging analysis was confined to the long and flat bones. CT scans were performed in five patients and MR imaging was performed in eight. Images were assessed for the following features on CT and MRI: the location and number of lesions; the presence of cortical destruction, endosteal scalloping, and a periosteal reaction on CT or MRI; the margin of soft tissue masses, the presence of bone marrow edema, and a "budding" appearance on MRI; and the presence of sclerotic margins or septations on CT. RESULTS: The involved skeletal sites were the pelvis (seven), femurs (five), humeri (two), tibias (two), fibula (one), clavicle (one), scapula (one), and sternum (one). Endosteal scalloping, a periosteal reaction, and a budding appearance were common on MRI or CT images. Although cortical destruction and the soft tissue lesion formation were rare, soft tissue masses had well-defined margins. CONCLUSIONS: Endosteal scalloping and a budding appearance with a periosteal reaction on CT and MRI may be helpful signs for differentiation of LCH from malignant tumors in adults.