Definition: Inverted (Schneiderian) papilloma is a locally malignant tumor that occurs in the mucosa of the cavity of the nose and paranasal sinuses. It acts like benign tumors but it can disrupt adjacent bone and it rarely turns malignant.
Incidence:
- 2% of all nasal tumors.
- Male: female is 3:1.
- Age: more common in the 5th – 6th decades.
Pathology:
Although it is histologically benign looking, it behaves in a locally destructive manner. It can erode bone and invade the maxilla and other adjacent structures.
- Arises from the lateral nasal wall.
- It arises from the sinonasal epithelium which has an ectodermal (not endodermal) origin (Schneiderian membrane.)
- In contradistinction to all other papillomata, it shows epithelial inversion into underlying stroma.
- Recurrence is common if wide surgical excision is not performed.
- Associated malignancy is 10%.
- Malignant transformation 5-15% to SCC.
Symptoms:
- Unilateral nasal obstruction (most common presentation).
- Unilateral nasal discharge
- Unilateral epistaxis
- Unilateral epiphora, facial swelling, proptosis etc. indicate tumor extension.
Signs:
- Unilateral firm reddish grey mass. It may be mistaken as nasal polyp or may actually be hidden amongst other nasal polypi.
- Endoscopic examination helps to determine the site of origin and extension.
Investigations:
- C.T./MRI.
- Biopsy.
Differential diagnosis: from other types of nasal polypi.
Treatment:
- Wide local excision (medial maxillectomy) via:
1) Endoscopic approach.
2) Lateral rhinotomy approach.
N.B. Irradiation is contraindicated as the tumor is not radio-responsive and because of the risk of inducing malignant transformation.