Plane Warts (Verruca Plana)
Plane warts show acanthosis and orthokeratosis in a basket weave pattern. There is no parakeratosis or papillomatosis. The cells in upper layers of stratum spinosum show koilocytosis and keratohyalin granules as wells as eosinophilic clusters of tonofilaments. The lesions undergoing regression exhibit apoptosis, keratinization, parakeratosis, and a superficial perivascular chronic inflammatory infiltrate.