Immunohistochemical demonstration and semi-quantitation of vascular endothelial growth factor in recurrent versus non-recurrent nasal polyps

OBJECTIVE: The expression of some growth factors in nasal polyps has been examined, although investigations addressing the reason for recurrence in some patients are lacking. Vascular endothelial growth factor (VEGF) is expressed by inflammatory cells, as well as by endothelial and epithelial cells of nasal polyps. To determine whether VEGF may play a role in the recurrence of nasal polyps, we aimed to compare VEGF expression in recurrent versus non-recurrent polyps. In addition, expression in polyps from asthmatic patients was compared with that in polyps from non-asthmatics. MATERIAL AND METHODS: A total of 30 patients with newly diagnosed nasal polyposis were included. Polypectomy was performed at enrolment in the long-term follow-up study. Fifteen patients had only 1 polypectomy (non-recurrence group; median observation period 81 months) and 15 had a median of 6.4 polypectomies (multiple recurrence group; median observation period 108 months). Five of 10 patients with asthma belonged to the non-recurrence group and 5 to the recurrence group. The polyp obtained at the initial polypectomy was examined for expression of VEGF by immunohistochemistry, using a polyclonal antibody. A blinded semi-quantitation and comparison of the intensity of immunolabelling were performed in recurrent versus non-recurrent polyps, as well as in asthmatics versus non-asthmatics. RESULTS: VEGF expression was seen as varying staining of the polyp surface and gland epithelium, as well as of the vessel endothelium and some stromal mono- and polymorphonuclear leukocytes. Semi-quantitation of the staining intensity showed no significant differences between recurrent and non-recurrent polyps, or between asthmatics and non-asthmatics. CONCLUSION: Our findings indicate that the level of immunohistochemical expression of VEGF in recurrent and nonrecurrent nasal polyposis is equivalent. Thus, the level of VEGF expression cannot predict a subsequent recurrence. The expression of VEGF is not upregulated in patients with asthma. Further studies are needed to determine the role of VEGF in nasal polyposis, with special reference to different stages of polyp formation, vascularization and growth.