Hematoxylin-eosin–stained sections revealed irregular epidermal hyperplasia with a vertical column of parakeratotic cells, the so-called cornoid lamella. Beneath the cornoid lamella, the granular layer was decreased, and there were many dyskeratotic and vacuolated cells. There was a diffuse lymphohistiocytic infiltrate in the papillary dermis. The epidermis on either side of the cornoid lamella was orthokeratotic, with a thickened granular cell layer. These findings were consistent with porokeratosis. The patient was treated with topical fluorouracil, with some improvement.