Juvenile nasopharyngeal angiofibroma
Juvenile nasopharyngeal angiofibroma (JNA) is a histologically benign , but locally invasive neoplasm occurring almost exclusively in adolescent males. These tumors are highly aggressive and are associated with significant morbidity and mortality due to its tendency to bleed.
This relatively rare tumor occurs in the second decade. Almost exclusively adolescent males are affected. The reported rate of incidence varies from 1/6000 (Harma 1959) to 1/50,000 (Hondousa etal 1954). The exact nature of the tumor and its etiology is not well known. Various theories have been propounded to explain the etiopathogenesis of JNA.
Ringertz theory: This theory was proposed by Ringertz in 1938. He believed that JNA always arose from the periosteum of the skull base. Som & Neffson (1940): believed that inequalities in the growth of bones forming the skull base resulted in hypertrophy of the underlying periosteum in response to hormonal influence. Bensch & Ewing (1941): thought that the tumor probably arose from embryoninc fibro cartilage between the basi occiput and basi sphenoid. Brunner (1942): Suggested an origin from conjoined pharyngobasilar and buccopharyngeal fascia. Marten et al (1948): Proposed a hormonal theory suggesting that these tumors resulted from deficiency of androgens or over activity of estrogens and that the hormonal stimulation is responsible for angiomatous components seen in JNA tissue. Sternberg (1954): Proposed that JNA could be a type of haemangioma like a cutaneous haemangioma seen in children which regresses with age. Osborn (1959): Considered two alternatives to explain the etiology of JNA. They proposed that the swelling could be due to either a hamartoma or residual fetal erectile tissue which were subject to hormonal influences. Girgis & Fahmy (1973): Observed cell nests of undifferentiated epitheloid cells or "Zell ballen" at the growing edge of angiofibromas. This appearance was more or less similar to that of paraganglioma. They considered JNA to be a paraganglionoma. The most accepted theory is that JNAs originate from sex steroid–stimulated hamartomatous tissue located in the turbinate cartilage. The proposed hormonal influence may explain why (rarely) some JNAs involute after puberty.
The proposed origin of the JNA is located along the posterior-lateral wall in the roof of the nasopharynx, usually in the region of the superior margin of the sphenopalatine foramen and the posterior aspect of the middle turbinate. Fetal histology confirms large areas of endothelial tissue in this region. Rather than invading surrounding tissue, this tumor displaces and distorts, relying on pressure necrosis to destroy and push through its bony confines. Intracranial extension is noted in 10-20% of cases.JNA are seldom seen in children below the age of 8. The rate of growth of tumor and period of maximum development coincides with rate of erectile tissue of penis, both increasing in size during the period of sexual development.
Grossly, angiofibromas appear as firm slightly spongy lobulated swelling with presence of nodules. The nodularity increases with age. Their color varies from pink to white. The part which is seen in the nasopharynx and which is covered by mucous membrane is invariably pink, where as those parts which have escaped to adjacent extra pharyngeal areas are often white or grey. On section the tumor is reticulated, whorled or spongy in appearence lacking a true capsule. The edges of the tumor are however, sharply demarcated and easily distinguishable from the surrounding tissues. Hence to reduce bleeding during surgical excision of the tumor the mass should be peeled off from its attachments and the mass should not be broken into. Microscopic appearance:
Microscopically the picture is of vascular spaces of varying shapes and sizes within a stroma of fibrous tissue. The relative proportions of the vascular and the stromal components change with the age of the swelling. In earlier lesions the vascular component stands out as an all pervasive feature, whereas in the more long standing tumors collagen predominates. It could also be seen that, as one strays away from the heart of the tumor the fibrous tissue element overshadows vascular element. The tumor is covered by squamous epithelium. In some cases pseudostratified columnar epithelium is seen side by side with the metaplastic squamous epithelium.Cellular infiltration is a common feature, particularly in the superficial parts of the tumor, underneath the epithelium. the infiltrates include, plasma cells, lymphocytes, polymorphs and eosinophils in varying proportions.
The structure of the tumor is made up of fibrous tissue elements and vascular channels. The fibrous tissue element is made up of cells which are spindle shaped, oval or round cells. In between these cells, the bundles of collagen fibres are seen running in different directions.The vascular channels of the tumor may be divided into 2 main types. One type which is seen in all cases is made up of spaces lined with one layer of endothelium and is free of any muscular coating. In the other type the vascular channels are made up of arteries with thick muscular coating.Mucous glands may be seen in the superficial parts of the tumor underneath the epithelial covering. In some patients nerve bundles could also be seen. In long standing tumors, there is a tendency towards gradual compression of the sinusoids so that the lining endothelial cells are pushed against each other like cords, where in others intravascular thrombosis occur.