Inverted papilloma is a rare benign sinonasal tumour, characterized by a potentially invasive nature. The lateral nasal wall represents the most common site of origin, whereas paranasal sinuses are quite frequently found to be involved by extension. In contrast, primary sinus inverted papillomas have rarely been reported. The present study describes an extremely rare case of inverted papilloma, isolated to the left sphenoid sinus, that was treated by a transnasal endoscopic procedure. The therapeutic approach chosen is discussed and the results of a two-year follow-up are also presented.

Inverted papilloma is the most common benign tumour of the nose and paranasal sinuses, and usually arises in the lateral wall of the nasal cavity and the middle meatus. The diagnosis is suggested on computed tomography (CT) when there is a mass continuous from the middle meatus into the adjacent maxillary antrum, through an expanded maxillary ostium. The mass may contain areas of high density or calcification, and there may be sclerosis of the wall of the affected sinus. The main advantage of magnetic resonance imaging (MRI) is in defining the extent of the tumour, and in differentiating it from adjacent inflammatory tissue, but there are no certain signal intensity or enhancement characteristics to help differentiate inverted papilloma from sinus malignancy. In the differential diagnosis, antro – choanal polyp, malignant sinus tumours and chronic rhinosinusitis and fungal disease need to be excluded. The combination of bone deformity and sclerosis with the typical antro – meatal mass suggests a slow – growing tumour such as inverted papilloma.

Surgery offers the optimum modality of treatment for inverted papilloma although a considerable range of operative approaches have been described. The results are presented in a cohort of 37 cases treated by both endoscopic and combined endoscopic and external approaches with a recurrence rate of eight and 21 per cent respectively. This series is compared with those in the literature and demonstrates that it is extent of disease which primarily determines the choice of surgical approach, with previous treatment, individual patient factors and surgical expertise as secondary determinants.

The results of a retrospective study of 22 patients with inverted papillomas resected by the endoscopic approach are presented with a follow-up of 33 to 96 months. Twenty-one patients had unilateral disease and one patient had bilateral involvement. None of the patients had orbital or cranial extension. One patient had synchronous carcinoma in situ. Eight patients had undergone previous surgical procedures. Following endoscopic surgery, six patients had residual disease requiring further revisions. Three of these six patients eventually required excision via limited external approaches. No patient required lateral rhinotomy or mid-facial degloving procedures. No complication occurredin any of the patients. The advantages of endoscopic surgery include precise determination of tumour extent, preservation of normal mucosa and bony structures and avoidance of external scars. Close endoscopic follow-up is mandatory to ensure early recognition and treatment of recurrent disease. Although the endoscopic approach is gaining popularity for the treatment of inverted papilloma, indiscriminate application may result in a high recurrence rate. The endoscopic approach should be performed by experienced surgeons and restricted to carefully selected patients with nasal, ethmoidal and limited maxillary disease. More extensive disease should be managed by radical external approaches or by combining endoscopic with limited external approaches.