The   diagnosis   of   HPV   warts   is   usually   clinical.   It   can   be confirmed by whitening of the mucosa when acetic acid is applied. This can be done with and without magnification, including colposcopy and anoscopy. Cytologic examination is used for mucosal evaluation. 42 Perianal, anal and penile intraepithelial neoplasia classically present as a velvety erythematous plaque or as a hyperpigmented well-defined plaque. A biopsy is helpful in establishing a diagnosis, particularly in verrucal lesions unresponsive to therapy or when warts have unusual features, such as hyperpigmentation, ulceration or excessive bleeding.[56]