Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. Risks of malignancy in inverted papilloma of the nose and paranasal sinuses Christian von Buchwald a and Patrick J. Bradley b Purpose of review The majority of inverted nasal papilloma are benign and treatment is by complete local surgical removal. There is an associated real, but small risk of malignancy, which may coexist at the time of presentation or develop at a later time. This article reviews some of the recent publications addressing the association of inverted papilloma with malignancy. Recent findings Neither the etiology of inverted papilloma nor the factors responsible for malignant transformation are fully elucidated to date. Inverted papilloma is associated with squamous cell carcinoma in approximately 10% of the cases. Malignancy may occur synchronously or metachronously. Summary Based on the literature, the rates of synchronous and metachronous carcinoma are 7.1 and 3.6%, respectively, although rates may be exaggerated due to a referral bias to tertiary centres. A thorough removal of all diseased mucosa is curative and a meticulous histological examination of the entire specimen is necessary. The working risk is approximately 10%. Recurrent disease and metachronous carcinoma can develop after a prolonged period of time. As most recurrences are due to incomplete resection, it is mandatory to perform a close follow-up, with biopsies performed when indicated. Life-long follow-up is recommended. Keywords inverted papilloma, nasal cavity malignancy, sinonasal papilloma, squamous cell carcinoma, treatment Curr Opin Otolaryngol Head Neck Surg 15:95–98. ß 2007 Lippincott Williams & Wilkins. a Department of Otolaryngology, Head and Neck Surgery, Rigshospitalet and Faculty of Health Sciences, University of Copenhagen, Denmark and b Department ORL-HNS, University Hospitals Nottingham, Queens Medical Centre Campus, Nottingham, UK Correspondence to Christian von Buchwald, MD, Department of Otorhinolaryngology, Head and Neck Surgery, Rigshospitalet, F 2071, University Hospital of Copenhagen, Blegdamsvej 9, 2100 Copenhagen, Denmark Tel: +0045 35452370; e-mail: Buchwald@rh.dk Current Opinion in Otolaryngology & Head and Neck Surgery 2007, 15:95–98 Abbreviations HPV human papilloma virus SCC squamous cell carcinoma ß 2007 Lippincott Williams & Wilkins 1068-9508 Introduction Referring to the World Health Organisation definition of 1991, sinonasal papillomas are benign epithelial neoplasia composed of well-differentiated ciliated columnar or respiratory epithelium with a variable degree of squa- mous differentiation. The papillomas of the sinonasal tract comprise three histological types: (1) inverted papilloma, (2) columnar cell papilloma and (3) exophytic papilloma. Exophytic papilloma originates mainly from the nasal septum, whereas inverted papilloma and colum- nar cell papilloma atypically arise from the lateral nasal wall or from within the maxillary sinus [1]. The term inverted papilloma describes the histological appearance of an endophytic or inverted growth of the epithelium into the stroma respecting the basement membrane that separates and defines the epithelial com- ponent from the underlying connective tissue stroma [2]. There are three characteristic attributes of inverted papil- loma; (1) its tendency to recur, (2) its destructive or bone remodelling capacity and (3) its propensity to be associ- ated with malignancy [1–4]. Histologically, inverted papilloma may be associated with a varying degree of atypia, dysplasia, carcinoma in situ, as well as frank squamous cell carcinoma (SCC) [2]. In a Danish demographical/epidemiological study [2] the incidence of sinonasal papilloma was shown to be approximately eight new cases per million inhabitants per year, representing the most common benign nasal neoplasia and up to 4% of nasal specimens in the patho- logical files. The mean age and gender distribution is typically over 50 years and 3 : 1 (M : F), respectively [3,4]. A staging system has been suggested by Krouse [5], based on tumour location in the nose and paranasal sinuses (Table 1), for reporting of inverted papilloma treated by endoscopic surgery. In cases that involve inverted papilloma beyond the sinuses or nasal cavity the tumour is upgraded to Krouse stage T4. The same stage T4 is achieved in the case of associated malignancy [5]. The latter might induce some contradictions as the lesion represents a totally different histology comprising another treatment modality and clinical course/prognosis. A comparison among the various Krouse stage T4 lesions is therefore troublesome [5]. Instead, it is more logical and recommendable to classify inverted papilloma with SCC together with other cases of SCC of the sinonasal tract. 95