Electron microscopic findings in four cases of nasopharyngeal fibroma.

Light and electron microscopic investigations of four cases of juvenile nasopharyngeal fibroma revealed characteristic structures; a fibrous stroma, an inclination to hyalinisation and formation of scar like tissue, a lacunar thin walled vascular component, large numbers of mast cells and of fibroblasts. The tumor fibroblasts contained different nuclear bodies and particles. There existed five different types of more or less complex spherical bodies. The previously described nuclear electron dense particles with an electron lucent halo could be divided into four groups measuring 60, 90, 150, and 300 nm in diameter. In addition to the previously described ultrastructural properties of the tumors, the nuclei of the tumor fibroblasts were found to contain virus like particles. These particles were less electron dense, measuring 40 to 55 nm in diameter and arranged in groups throughout the nucleoplasm; they were different from chromatin condensations and from perichromatin granules. The structure and the size of the smallest particles was not comparable with the other nuclear inclusions.