There are many differences and similarities between the conditions syphilitic chancre and chancroid
Similarities
Both originate as pustules at the site of inoculation, and progress to ulcerated lesions
Both lesions are typically 1–2 cm in diameter
Both lesions are caused by sexually transmissible organisms
Both lesions typically appear on the genitals of infected individuals
Both lesions can present at multiple sites and with multiple lesions
Differences
Chancre is a lesion typical of infection with the bacterium that causes syphilis, Treponema pallidum
Chancroid is a lesion typical of infection with the bacterium Haemophilus ducreyi
Chancres are typically painless, whereas chancroid are typically painful
Chancres are typically non-exudative, whereas chancroid typically have a grey or yellow purulent exudate
Chancres have a hard (indurated) edge, whereas chancroid have a soft edge
Chancres heal spontaneously within three to six weeks, even in the absence of treatment
Chancres can occur in the pharynx as well as on the genitals