A light and electron microscopic study of an atypical calcifying odontogenic tumor containing "amyloid".

Abstract

Abstract. The light and electron microscopic appearances of an atypical calcifying odontogenic mandibular tumor containing “amyloid” arc presented. In a part of the tumor, PAS‐reactive hyalin eosinophilic material which showed green dichroism by polarized light after Congo Red staining, and also hematoxylinophilic mineralized portions were found. By electron microscopy the hyalin material revealed a fibrillar structure. The fibrils had a median diameter of 100 Å. and were short and curved with some apparent outer modularity. They differed morphologically from other unidentified extracellular and intracellular densely packed fibrils of about 85 Å in diameter, from collagen fibers and from a small number of elastic fibers found in the connective tissue. Apparent calcification had occurred in aggregates of the 100 Å fibrils to produce‐ a linear and angulated electron‐dense front. Calcification within epithelial cells of the tumor, and calcification in irregular foci around collagen fibers were also found.Quite different histopathological appearances were noted by light microscopy in different parts of the tumor. An anterior region contained numerous islands with large areas of odontogenic epithelium with peripheral ameloblast‐like cells and also solid sheets of cuboidal epithelial cells resembling in some ways those of the calcifying epithelial odontogenic tumor.The upper or posterior region of the tumor contained marked cavernous hemangiomatous elements separated by a loose and often myxoid stroma. Metaplastic cartilage formation had occurred in one part of it. The third molar tooth was located near the coronoid notch. The tumor, although not precisely classified, appeared to be an atypical ameloblastic fibro‐odontoma.