Warts are usually diagnosed based only on their appearance.
In rare cases, more testing is done. If the diagnosis of a skin condition is unclear or if you are at high risk for having skin cancer, your doctor may take a sample of the growth and examine it (a skin biopsy). A biopsy is usually done if a skin growth is darker than the skin surrounding it, appears as an irregular patch on the skin, bleeds, or is large and growing rapidly.
Proper diagnosis of plantar warts is important. Some wart treatments can cause scarring.