Chondroma, which arises from medullary canal, is called enchondroma and if it develops from bone surface, it is referred to as periosteal or juxtacortical chondroma. Multiple endochondromatosis (Ollier disease) involve large and small tubular and flat bones and are found in epiphysis, metaphysis and shaft.
Juxtacortical chondroma are small lesions of less than 3cm in size and well-defined saucer shaped defect with underlying sclerotic cortex.
Considering the radiologic and histopathologic features, the location and the age of the patient, this lesion was most consistent with the diagnosis of a juxtacortical chondroma (periosteal chondroma).
Juxtacortical chondroma of the leftproximal medial metaphyseal tibia
In this young, female patient with left-knee pain associated with a cartilaginous lesion of benign appearance, the relatively rare juxtacortical location, with associated cortical break, raises concern for a low-grade cartilaginous malignancy, such as a juxtacortical chondrosarcoma as opposed to the benign juxtacortical chondroma.
A juxtacortical chondroma may extend into the soft tissues without infiltration.
Clinically, presentation of a juxtacortical chondroma may be with a firm, nonmobile, slowly growing, palpable mass that may have pain that increases with lesion size.
Radiographically, a juxtacortical chondroma usually appears as a small, cortically based, radiolucent oval/oblong bony defect, longer than wide with little or no calcification.
A juxtacortical chondroma must be differentiated from a juxtacortical (or periosteal) chondrosarcoma, particularly as a juxtacortical chondroma often demonstrates high cellularity, binucleated cells, hyperchromatism and a myxoid appearance.