The nature of the eosinophilic and laminated masses in the adenomatoid odontogenic tumor: a histochemical and ultrastructural study.

The eosinophilic and laminated masses in AOT were investigated with the light and electron microscope in two cases. The results showed that the eosinophilic amorphous masses were heterogenous and consisted mainly of three types of fibrils. These were: thin collagen, electron dense fibrils probably resulting from degradation of collagen and masses of amyloid filaments with or without collagen fibers in normal and degraded forms. In addition some of the eosinophilic deposits resulted from changes surrounding blood vessels which led to deposition of either collagen or fine filaments arranged into layers around these vessels. In all these areas there was a peripheral layer of fine filaments perpendicular to the epithelial basal lamina, similar to that found in early dentin formation. This layer may be responsible for the reticulin staining found in this tumor. On the other hand the great majority of the laminated masses represented calcified amyloid with or without areas of calcified degraded collagen which were indistinguishable from amyloid. The results suggest that the various fibrils forming the eosinophilic masses in AOT are probably related and may be the result of changes in blood vessels. They also revealed that calcification involves mainly amyloid.