Nasopharyngeal angiofibroma: true neoplasm or vascular malformation?

Nasopharyngeal angiofibromas (NA) are rare tumor-like lesions characterized by architecturally irregular vessels set in a fibrous stroma. The unique morphology, the strong predilection for male adolescents, and the uncertainty about its etiology contributes to significant confusion regarding the classification of NA, which still has not been solved today. Based on immunohistochemical and electron microscopic examinations, we demonstrate in detail the various unusual vascular architectural features of NA. They represent discontinuous vascular basal laminae, focal lack of pericytes, and pronounced irregularity of the smooth muscle layers. In thick smooth muscle layers and pads, the orientation of muscle cells is frequently disturbed, and the individual cells differ in size and shape. Occasionally, the muscle layers disperse peripherally into individual cells, creating the impression of vessel-independent smooth muscle cells within the stroma. The summation of all morphological irregularities demonstrated in this paper allows the conclusion that NA represent vascular malformations.