A chancre is a painless genital ulcer most commonly formed during the primary stage of syphilis. This infectious lesion forms around 21 days after the initial exposure to Treponema pallidum, the gram-negative spirochaete bacterium causing syphilis, but can range from 10 to 90 days. Without treatment it may persist for two to six weeks before healing. Chancres transmit syphilis through direct physical contact. These ulcers usually form on or around the anus, mouth, penis and vulva.