Juvenile nasopharyngeal angiofibroma. An ultrastructural study

Four clinically and histologically typical juvenile nasopharyngeal angiofibromas were examined by electron microscopy. An original tumor, first, fifth and sixth recurrence, respectively, were studied. The stromal cells of the early stage tumors (original and first recurrence) contained lobulated nuclei, large intranuclear inclusions, variable amounts of rough endoplasmic reticulum (RER) and thin filaments, hemidesmosomes, focal basal lamina and prominent pinocytotic vesicles. In the later (fifth and sixth recurrence) stage tumors, the nuclei often had serrated margins and smaller inclusions. The cytoplasm contained dilated cisternae of RER and numerous thin filaments with dense bodies. Hemidesmosomes and pinocytosis were diminished; no basal lamina was observed. These observations indicate that the stromal cell of this tumor undergoes some structural modulation between its early and late stages. The nuclear granules appear to diminish in size with time. The cells in both stages possess features common to both fibroblasts and smooth muscle cells. Such a hybridized mesenchymal cell, i.e. “myofibroblast”, has been previously described for other fibroproliferative lesions, although its presence in this tumor is of uncertain significance. Additional electron microscopic studies of fibrous and soft tissue lesions are needed to further characterize the prevalence and perhaps the origin of the myofibroblast.