ADENOMATOID AMELOBLASTOMA An analysis of nine cases by histopathological and electron microscopic study

1. Nine cases of adenomatoid ameloblastoma were reviewed and analyzed from the clinical and pathological points. Moreover, the tumors were studied electron microscopically and histochemically. 2. The adenomatoid ameloblastoma was more common in female and mostly occurred in the second decade of life. The lesion occurred frequently in the incisor-cuspid-premolar regions, and the mandible was more affected than maxilla in our cases. 3. A direct transition between the duct-like lumen and the degenerated stroma was demonstrated histologically. By electron microscope, basal lamina along the lumen was ascertained and fibrillar structure of the connective tissue was found in the lumina. It seems reasonable to assume that the duct-like structure is considered to be not a genuine duct but be formed by degeneration of the stromal tissue. 4. The real nature of the eosinophilic substance in the lumina could not be determined. By electron microscope, it appeared to be amorphous or fibrillar structure. The substance in the parenchyma might be different from that in the lumina in the chemical composition. 5. Most of the calcified substance is thought to be dystrophic calcification. 6. Histogenetically, enamel organ or its cell rests might be the most reason able origin, but definite derivation could not be determined. 7. Histochemically, acid phosphatase activity was found in the spindle cdl areas of the tumor