The cases of seven patients who had a lytic lesion that was
histologically similar to a metaphyseal fibrous defect (non-ossifying
fibroma) of bone were studied. The patients all were adults and had pain
without a fracture. These features were considered distinctive for the
lesion, which has the same histological appearance as benign fibrous
histiocytoma of soft tissue. The lesion is a benign tumor with fibroblastic
and histiocytic differentiation. This picture may be seen in foci in other
lesions of bone (aneurysmal bone cyst, fibrous dysplasia, and giant-cell
tumor). Ten cases of giant-cell tumor of bone that had a large component of
the same foci were also reviewed. It should be emphasized that these areas
are secondary reactive tissue rather than the true neoplastic tissue of
benign fibrous histiocytoma.