Sections demonstrate two histologically distinct lesions.
The smaller of the two lesions shows extensive invagination of basement membrane bound nonkeratinizing squamous and pseudostratified ciliated columnar epithelial cells into the underlying stroma. Numerous intraepithelial microcysts containing polymorphonuclear leukocytes are present. Other sections demonstrate a predominantly exophytic or papillary lesion composed of well differentiated, cytologically bland, squamous epithelium with extensive parakeratosis and absent stratum granulosum. The base of the lesion shows rounded or bulbous rete pegs with broad pushing borders. The underlying stroma shows only minimal inflammation and in some areas myxomatous change.