Skull Base Inverted Papilloma: A Comprehensive Review

Table 1

Comparing IP to other Schneiderian papilloma.

Papilloma	Fungiform	Inverted	Oncocytic Schneiderian
Former name/synonyms	Septal	Ringertz	Cylindrical, columnar
Prevalence %	50	47	3–5
Origin	Nasal septum	Lateral nasal wall and paranasal sinuses	Lateral nasal wall and paranasal sinuses
Epithelium; pattern of growth	Everted, exophytic	Infolded, endophytic
Microscopy	Thick squamous epithelium and, less frequently, respiratory epithelium arranged in papillary fronds	Thickened squamous epithelium admixed with mucocytes and intraepithelial mucous cysts	Multilayered epithelium with an eosinophilic cytoplasm among which intraepithelial mucin cysts
Age group	Younger	50~60	30~80
Malignancy	35% have invasive squamous cell carcinoma	Locally aggressive, extending into the sinuses, the orbit, nasopharynx [20], or meninges. Three to 24% (mean 13%) may have an invasive focus of squamous cell carcinoma	14%~19%; Malignant change potential
	25% multifocal		Mixed with typical inverted papilloma