Nasopharyngeal angiofibroma: an immunohistochemical study of 32 cases.

Thirty-two cases of nasopharyngeal angiofibroma, including 2 recurrences, all of which had been excised from males between 7 and 25 years, were subjected to systematic immunohistochemical study. Most of the tumour vessels, which lacked elastic laminae, were characterized by vascular walls of irregular thickness and variable muscle content. In places endothelial cells were only separated from the stroma by a single attenuated layer of contractile cells, whereas elsewhere the same vessel walls showed pad-like thickenings of their muscle coat. All cells of the vessel walls showed immunoreactivity for vimentin and smooth muscle actin, whereas desmin-positive cells were present only in small numbers in some vessels, generally those with thicker muscle coats. The stromal cells were decorated by vimentin antibodies only; however, in some more fibrotic hyaline areas the stromal cells displayed also reactivity for smooth muscle actin. In most cases S-100 protein-staining disclosed many nerves, and this accentuated their parital distortion by tumour tissue. Our findings provide an extended insight to the morphology of angiofibromas at this site, particularly highlighting the irregularity of their vascular walls, which, taken together with the lack of elastic laminae and elastic stromal fibres, can be held responsible for the typical pronounced tendency for haemorrhage in these lesions.