Background: Inverted papilloma is a benign sinunasal tumor, characterized by aggressive nature and tendency to recur. This tumor also has a significant malignant potential (10%). In spite of extensive research in the past the origin of inverted papilloma is not known.
Methods: A retrospective analysis of the clinical data of 28 patients suffering from inverted papilloma of the nose and paranasal sinuses with regard to symptoms, clinical examination, computed tomography findings, and operative management was performed. Furthermore, immunohistochemical examinations of the cytokeratin profile of 12 specimens were carried out.
Results: The most presenting symptoms were unilateral nasal obstruction (17.61%) and rhinorrhea (7.25%). Polyposis was seen endoscopically in 19 cases (68%), so that in many patients in inverted papilloma became suspicious in the CT scan. The surgical therapy was dictated by the extent of the tumor, so that the tumor was treated by lateral rhinotomy (n = 17), midfacial degloving (n = 5), endonasal endoscopic surgery (n = 5), and craniofacial resection due to an infiltration of the frontal skull base (n = 1). An immunohistochemical analysis of the cytokeratin profile revealed for the first time that the inverted papilloma, when compared to the normal surface epithelium of the nasal cavity and the paranasal sinuses, exhibits increased expression of cytokeratin 5, typical for basal cells, and cytokeratin 13, typical for squamous epithelial cells.
Conclusions: Based on our results we recommend that the endonasal approach is reliable for processes restricted to the middle nasal meatus and the anterior and middle ethmoid cells. Inverted papilloma of the frontal sinus, retrobulbar and supraorbital ethmoid cells, and laterocaudal parts of the maxillary sinus should be resected via lateral rhinotomy or midfacial degloving. The findings of immunohistochemical examinations suggest that inverted papilloma is derived from a cytokeratin 5-immunoreactive cell of the basal layer of the mucosa.