“Malignant conversion of perianal warts may occur in some cases, as well as from nail warts or from plantar warts. Papillomas in the mouth , and in the larynx may become cancer. HPV is associated with development of skin cancer in HIV infected people”.
“There may be some enhanced risk of skin warts exposed to U.V. light developing into invasive squamous cell carcinoma (very rare).”
there are about 100 types of papilloma viruses, and they tend to be quite specific - the skin types are not the nasty ones implicated in cancer. From my reading, skin warts are quite harmless except in very rare cases