Putative histogenesis of post nasal angiofibroma.

Abstract

Inspite of the histological resemblance, these tumefactions do not behave like true neoplasms. Harma (1959) believed their histogenesis from angioblasls. Taxy (1977) regards the fihroblasts as the main stroma cell which has resemblences like those of the granulation tissues, and hence appear to be hybrid fihroblasts. Vascular and fibrous element could be produced by any mesodermal "stem cell" (Shenoi. 1989). Therefore both fihroblasts and angioblasts may be inter-convertible.The cavernous element of tumour suggest it to be the hamartoma. The posterior part of nose and turbinates have very vascular and cavernous mucosa. The hamartomas are influenced by endocrine factors and growth hormones. The mesodermal element of this tumour also appear to have androgen receptors (Lee et al, 1980). These endocrine factors could be the initial triggering mechanisms, for their development appear most rapidly at the parapubertal age. The tumour is also influenced by peri-and apocrine factors. The eytogenic growth factors are locally available. The neoangiogenesit is, perhaps, influenced by these factors, which also induce destruction of basement membrane of vessels, migration and mitosis of angioblasts and formation of new blood vessels of capillary and larger sizes. The maturation of tumour appears to he heralded by reduction in endocrine factor tike growth hormone and establishment of sex hormones beyond the puberty. Further it is accelerated by local peri-and apocrine factors contributed by macrophages, lymphocytes etc. Those cases with heavy infiltration, therefore, have more often the signs of maturity like collagenisation, encapsulation, obliteration of vascular elements and necrobiotic phenomenon. These are exceptional tumours estntially observed amongst para-puberal males, having easy bleeding tendency and multidirectional extensions. They destroy the hones of skull and occupy adjoining cavities including cranial extensions in almost 20% cases (Ward et al, 1974). There is high recurrence rate (20 to 50% after initial excision). There are different views regarding their aetiopathogenesis, but none is able to explain all its features. These are considered to be inflammatory or allergic in origin (Willis, 1953), hyperplastic tissue reactions (Harma, 1959), due to androgen deficiency (Martin et al., 1948), vascular malformation (Osborn,1959) and hamartomas (Mishra & Bhatia.1964). Lately, micro-histological and marker techniques and better understanding of oncogenesis, have been available which give more insight in explaining its behaviour. In view of controversies, a retrospective study of more than 300 cases of angiofibromas is carried out to formulate a putative pathogenesis of this tumour and its peculiar behaviour.