Author: Assoc Prof Patrick Emanuel, Dermatopathologist, Auckland, New Zealand, 2013.
Verruca plana (plane warts) are typically associated with human papillomavirus (HPV) types 2, 3, and 10. HPV 5 may be seen in human immunodeficiency virus (HIV)-positive patients.
Sections show orthokeratosis, mild papillomatosis, and mild acanthosis (figure 1). There is usually no or minimal parakeratosis. The dermis is normal. The upper epidermis shows hypergranulosis and numerous koilocytes (figures 2, 3). Regressing lesions may show a lymphocytic response and keratinocyte apoptosis.
Special investigations are generally not required.
Verruca vulgaris – Typically shows marked papillomatosis with parakeratotic foci. Distinction can be difficult in involuting verruca vulgaris.
Squamous cell carcinoma in situ – Full thickness keratinocytic atypia should be carefully ruled out at high power examination.
Epidermodysplasia verruciformis – This condition typically shows verruca plana-like changes. Characteristic blue-grey cytoplasmic changes are seen.
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