Ameloblastic fibrosarcoma of the jaws--report of three cases. Clinico-pathologic, histoenzymological and ultrastructural study.

The ameloblastic fibrosarcoma is a rare variety of neoplasm. Three new cases reported here occurred within preexistent benign odontogenic tumors (ameloblastic fibroma or fibro-odontoma). These large, osteolytic tumors, spreading to adjacent soft parts, recurred after surgical treatment in two cases. One of them had a lethal course, with pleuro-pulmonary, mediastinal lymph node and hepatic metastases. Histologically, these sarcomas show a malignant mesenchymal component and few benign ameloblastic islands, which often disappear after one or several recurrences. Histoenzymologically, a high level of alkaline phosphatase and ATPase activities is always present, a feature not present in common fibrosarcomas. The ultrastructural study demonstrates, in analogy with odontogenic myxomas, clear cells provided with numerous microfilaments, secretory cells and also some fibroblasts and myofibroblast-like cells. In addition to these pleomorphic cells, a great number of peculiar granular cells with numerous lysosomal bodies were also found. The histogenesis of these tumors in unknown. Perhaps the epithelial component, being unable to assume its functions of organization, may initiate the malignant transformation of its odontogenic mesenchyme.