Ultrastructure of nasopharyngeal angiofibromas

Nasopharyngeal angiofibromas from one female and seven male adolescents were studied by light and electron microscopy. Mast cells comprised a conspicuous, uniform component of all the tumors. Electron microscopic study disclosed the variation in structure of mast cells. The granules tended to be grouped into compact, circular bodies composed of punctate, filamentous or amorphous material or of stratified lamellae which, on transverse section were of a scroll‐like configuration. Many granules were not within cells but scattered individually throughout the stroma. Others appeared to have been phagocytized by macrophages. Variation in the thickness of vessel walls was due to variation in the number of layers of smooth muscle cells. In addition, numerous smooth muscle cells were present in the stroma, independent of vessels. The angiofibroma from a female was indistinguishable, in histology and ultrastructure, from the tumors occurring in males. It is concluded that mast cells and smooth muscle cells constitute integral cellular components of nasopharyngeal angiofibromas and that the angiofibromas in females, though rare, do indeed occur and are identical in their ultrastructure to the typical tumor in males.