sphenopalatine foramen with extension to the upper medial pterygoid plate [118]. Nasopharyngeal angio-fibromas are unencapsulated, lobulated, firm, grey to tan tumours. Abnormal blood vessels of different sizes and irregular architecture in arbitrary arrangement are embedded in a myofibroblastic stroma. The proportions of both components can vary considerably (Fig. 6.3). The vascular component can be divided into small sinusoidal vessels and large muscular vessels with irregular and incomplete smooth muscle layers with abrupt transitions from a muscular coat to an endothelial cell lining only. Irrespective of their architecture, all vessels are lined with a continuous layer of single regular endo-thelial cells. The stromal component varies in amount and cellularity. The majority of stromal fibroblasts are plump and stellate, others assume an elongated spindled configuration. Mitoses are inconspicuous. The majority of stromal cells react with vimentin only, while a subpopulation is characterised by co-expression of vimen-tin and smooth muscle actin.

Despite the body of literature, there is still uncertainty about the aetiology of nasopharyngeal angiofibromas. They have been called haemangioma and vascular ham-artoma arising from ectopic vascular tissue of the inferior turbinate. Other theories have included overgrowth of paraganglionic tissue, hyperplasia in response to allergic stimulus, fibromatosis, teratoma arising from the occipital plate, but also an androgen-dependent neoplastic process due to an imbalance of the pituitary-andro-genital system [9]. A concomitant presentation of naso-pharyngeal angiofibromas and the familial adenoma-tous polyposis syndrome has been reported in 4 out of 825 patients at the Johns Hopkins' Registry for familial colonic polyposis [47, 62]. A mutation in the APC gene, however, was not demonstrated in 9 patients with na-sopharyngeal angiofibroma, and a comparative genom-ic hybridisation study describes a normal chromosome 5 in 3 patients with nasopharyngeal angiofibroma [70, 170]. The same study reports gains on chromosome 8 at the site of the genes for TGF-fi inducible early growth response and LYN (v-yes-1 Yamaguchi sarcoma viral-related oncogene homologue), and on chromosome 6, on which the gene for the vascular endothelial growth factor is located [170]. The additional complex gains on the X chromosome and losses on the Y chromosome may explain the exclusive occurrence in male patients. The interpretation of nasopharyngeal angiofibromas as a vascular malformation has proved to be the most consistent theory over the past few decades. A recent publication proposes that nasopharyngeal angiofibromas arise from an embryological vascular remnant of the first pharyn-geal arch artery, which normally regresses to a vascular plexus, giving rise to the maxillary artery [75, 153, 171]. Incomplete involution leaves behind vascular remnants in the lateral nasal wall in the area of the sphenopala-tine foramen from where nasopharyngeal angiofibro-

mas originate. This theory explains the abnormal vascular structures and the complex anatomical extensions of nasopharyngeal angiofibromas. The growth stimulation during puberty and the restriction to males remain unexplained by this theory, however. Treatment of na-sopharyngeal angiofibromas is surgical after embolisa-tion, although radiation therapy and hormonal therapy have been used extensively in the past [15, 37]. Nasopha-ryngeal angiofibromas have no malignant potential, except for radiation-related malignant transformation.

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