Fibrous cortical defect. Cortical fibroma.

The fibrous cortical defect is a common benign bone tumour. In some locations, particularly the neck of femur, it can be regarded as a normal variant. In that location, it is usually below 1cm. The lesion has the usual narrow endosteal zone of transition between normal and abnormal bone. The tumour is well marginated. It elevates the cortex a little and thins it. The lesion is well defined. No treatment is required and the lesion usually resolves, in that these lesions are very rarely seen in adults. A healed fibrous cortical defect can be dense and is occasionally seen in adults as a coarse calcific eccentric density in the bone. It can usually be distinguished from the calcification in an enchondroma by the scalloped thinning of the cortex from the underlying cartilage tumour.