Appearance and Diagnosis

Clinically, warts are classified according to their location and appearance on the skin. Warts can appear anywhere on the body; only those appearing on the bottom of the foot are referred to as plantar warts. Warts are usually painful when they are on a weight-bearing surface or at a place of increased irritation.

Plantar warts are endophitic in nature, meaning they grow into and not out of the skin. Moreover, being on a weight-bearing surface (i.e., the ball of the foot, bottom of the toes, and/or heel), plantar warts are constantly pushed deeper into the skin just by standing. Likened to icebergs, only a small portion of a wart can be seen above the skin surface; it is impossible to know how deep it goes simply by looking at it. This makes treatment very difficult, as the wart may be deeper than the selected treatment can penetrate.

Warts can appear as small, raised flesh-colored lesions with a cauliflower shaped head, or as flat, callused islands or patches. Plantar warts typically appear as the latter. They may appear alone or in clusters known as "mosaic" warts. Left untreated, a single wart can grow to more than an inch in circumference. Plantar warts can look and feel very similar to simple callus formation (a protective mechanism of the body); thus distinguishing between the two can be quite difficult.

Careful clinical examination can reveal several features that differentiate a wart from a callus. First, warts tend to be more painful when squeezed from side-to-side, whereas a callus will hurt more on direct pressure. Second, the trained eye of your doctor may appreciate a discontinuation of the skin lines indicative of a wart; calluses will often have skin lines (like fingerprints) intact. Last, warts have a very superficial blood supply comprised of tiny capillary networks. These capillaries may appear as minute black specs under bright light, but are best visualized when the doctor trims away (often without pain) the dead skin. Because the blood supply is very superficial, warts will bleed in a pinpoint fashion. Calluses do not have their own blood supply and therefore do not bleed as frequently. It should be noted that the pinpoint bleeding associated with a wart might also appear with mere scratching of the lesion. Since the virus is contained in the blood, scratching to the point of bleeding could transfer the virus to another location (like your scratching finger).

In some instances a doctor may want to biopsy a lesion in order to ensure a diagnosis. In rare instances warts can transform into cancerous lesions, especially in individuals with compromised immune systems. It is always a good idea to have any suspicious or long-standing lesions examined by your physician.