Peering beneath the surface: Juxtacortical tumors of bone (part I).

Juxtacortical or surface tumors of bone are neoplasms arising from or just outside the cortex, and are composed of different histologic types. Although the imaging appearances of these lesions have similarities to their intramedullary counterparts, their location alters their radiographic and MR characteristics, creating difficulties in diagnosis. Meanwhile, several non-neoplastic lesions, such as stress reaction/stress fracture and indolent infectious processes, compound the differential diagnosis. Neoplastic juxtacortical lesions of bone have been classified into five categories: cartilaginous, fibrous, lipomatous, osseous, and metastatic tumors. Our goal in part one of this review is to illustrate the characteristic radiographic, CT and MR imaging features of various juxtacortical neoplasms, including pathognomonic imaging findings that can aid in diagnosis, and to develop an appropriate differential diagnosis for surface lesions based on imaging characteristics, lesion location and patient age.