Inverted Papiloma
A benign endophytic proliferation of squamous epithelium caused by infection with a papillomavirus.
Gross Appearance:
•Well demarcated from the adjacent dermis and panniculus adiposus
•Finger-like projections extend into the center of a craterlike invagination
•Keratinous material accumulates in the central portion of the mass
•An association with the overlying epidermis may be seen at the lip of the crater
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Histology:
•Tumor has the histologic appearance described for the papilloma
•However; mass is endophytic, so the papillae extend into the lumen of a crater produced by an
invagination of the epidermis
•May be found in the subungual (nailbed) area, where they must be distinguished from subungual
keratoacanthomas
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