Abstract
1. Histochemical staining and correlated biochemical estimations of five hydrolytic enzymes were done on eighteen benign and twenty malignant fibroblastic lesions of bone and soft tissue.
2. Alkaline phosphatase activity was moderate in a fibroma and very high in fibrous dysplasia. In a typical fibrosarcoma the fibroblasts showed no enzyme activity and estimations were low. Exceptions indicated an osteogenic potential in the tumour.
3. ß-glucuronidase, leucine aminopeptidase, and to a less extent non-specific esterase, were more active in malignant than in benign lesions, and the highest activities were found in sarcomata arising in Paget's disease of bone.
4. Acid phosphatase showed no correlation with malignancy and was generally unremarkable except for high activity in osteoclasts, but was raised in two sarcomata that occurred after irradiation of giant-cell tumours.
5. A non-osteogenic fibroma and a fibrous cortical defect, though poorly represented in this series, are not uncommon; they sometimes lead to pathological fracture, but sarcoma is very rare in such lesions. They tend to show more alkaline phosphatase than fibrosarcoma but not the very high activity of fibrous dysplasia, which is related to its osteogenic potential.
6. Fibrous dysplasia most often presents in the five to fifteen age group but seldom leads to malignancy, though this may occur, usually as osteosarcoma, which has a similar high content of alkaline phosphatase. Fibrosarcoma is typically negative or very weak in this enzyme: the exceptional cases with high activity were tumours which were in part osteosarcoma. Generally the demonstration of high alkaline phosphatase activity in a fibroblastic lesion of bone, in the absence of trauma or inflammation, suggests the diagnosis of fibrous dysplasia.
