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Total

728 (100%)

452 (62%)

42 (6%)

Although a viral origin of inverted papil-lomas has long been suspected, viral inclusions have never been unequivocally demonstrated by light or electron microscopy. In addition, they are almost invariably negative when stained for human papillomavirus (HPV) by the immunoperoxidase technique. HPV genomes, however, have been demonstrated in inverted papillomas by in situ hybridization or the polymerase chain reaction, particularly HPV 6 and 11, sometimes HPV 16 and 18, and exceptionally, HPV 57. The frequency of finding the virus by these specialized techniques is highly variable, ranging anywhere from 0-100% {127}. In a collective review of 341 inverted papillomas evaluated for the presence of HPV by a variety of sophisticated molecular techniques, 131 (38%) were positive. Whether the virus is a passenger or etiologically related to the papilloma is unclear {1596}. Epstein-Barr virus (EBV) DNA has been identified in 65% of inverted papillomas by polymerase chain reaction (PCR), raising the possibility that this virus might be involved in its pathogenesis {1596}. A subsequent study utilizing in-situ hybridisation found no evidence of EBV in the tumour cells, suggesting that the reported PCR positivity might be related to the presence of EBV-positive lymphocytes in the tissues {842}. There is no known association of inverted papilloma with allergy, inflammation, smoking, noxious environmental agents or occupation {1158}.

Fig. 1.28 Inverted papilloma. A Specimen removed intact. Note the opaque yellow-tan nodular polypoid appearance. B Cut surface of the lesion shown in A. Close inspection shows well-demarcated islands of epithelium which extend endophytically into the stroma.

Fig. 1.27 Inverted papilloma. Coronal CT. The tumour bows the bone. The calcification (white arrowhead) may represent a sclerotic fragment of inferior turbinate.

Fig. 1.28 Inverted papilloma. A Specimen removed intact. Note the opaque yellow-tan nodular polypoid appearance. B Cut surface of the lesion shown in A. Close inspection shows well-demarcated islands of epithelium which extend endophytically into the stroma.

Localization

Inverted papillomas characteristically arise from the lateral nasal wall in the region of the middle turbinate or ethmoid recesses, and often extend secondarily into the sinuses, especially the maxillary and ethmoid and, to a lesser extent, the sphenoid and frontal. Isolated lesions of the paranasal sinuses without nasal involvement however, do occur. Almost none arise primarily on the nasal septum {1297}.

Exceptionally, inverted papillomas may arise in sites other than the sinonasal tract. They have been recorded in the middle ear-mastoid {2757}, pharynx {2499}, nasopharynx {81}, and lacrimal sac {2217}. It has been suggested that ectopic migration of the Schneiderian membrane during embryogenesis could account for these aberrant papillomas in sites contiguous with the sinonasal tract

{1158}. Whether all of these ectopic cases are bona fide inverted papillomas is uncertain.

Although overwhelmingly unilateral, rare cases of bilateral inverted papillomas have been described {211}. Such occurrence, however, should always arouse the suspicion of septal erosion and perforation from unilateral disease.

Clinical features

Signs and symptoms

Nasal obstruction is the most common presenting symptom. Other manifestations include nasal drainage, epistaxis, anosmia, headaches (especially frontal), epiphora, proptosis, and diplopia. Pain, on the other hand, is an uncommon initial complaint, occurring in only about 10% of all cases. When present, it should always arouse suspicion of secondary infection or malignant change.

On physical examination, inverted papil-lomas present as pink, tan, or grey; non-translucent; soft to moderately firm, polypoid growths with a convoluted or wrinkled surface.

Imaging

Findings on imaging vary with the extent of disease. Early on, there may be only a soft tissue density within the nasal cavity and/or paranasal sinuses. Later, with more extensive disease, unilateral opaci-fication and thickening of one or more of the sinuses is common, as are expansion and displacement of adjacent structures. Pressure erosion of bone may also be apparent and must be distinguished from the destructive invasion associated with malignancy, such as de novo carcinoma or carcinoma arising in and/or associated with an inverted papilloma.

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