[Benign fibrous histiocytoma of the distal femoral metaphysis. Differential diagnosis between neoplasm and growth disorder with identical morphology].

The typical radiologic finding of a "non-ossifying fibroma" of the distal femoral metaphysis was seen in a 17-year-old female patient with pain in the distal femur. The rapid development of this lesion was confirmed on the basis of earlier radiographs performed to clarify other complaints. Since the lesion had developed in no more than 34 months, with pronounced scintigraphic and MRI signal intensity, particularly in the late phase, and pain had prompted the patient to seek examination, the cause was assumed to be a neoplasia rather than a growth disorder. Histopathological examination revealed a proliferative fibrohistiocytic lesion which was histologically different from a malignant fibrous histiocytoma. The finding indicates that in the differential diagnosis between non-ossifying fibroma and benign fibrous histiocytoma in cases with identical localization, pain and the intensity of the scintigraphic signal may well be the key to further action: since benign fibrous histiocytomas may be regarded as genuine neoplasias, the question of malignancy should also be clarified beyond doubt.