The ulcers of Behcet's are painful and recurrent, and part of a systemic syndrome, unlike the classic single, painless chancre of primary syphilis.
The ulcer of chancroid is distinguished by being painful and soft, with a ragged, undermined border and purulent base, the opposite of a syphilitic chancre.
Genital ulcers from EBV are rare, painful, and diagnosed by exclusion, lacking the classic induration of a chancre.
This is a recurrent lesion in the exact same spot triggered by a drug, not an infectious ulcer.
Herpes is distinguished by its initial grouped vesicles that evolve into multiple, painful, shallow ulcers, unlike the typically single, painless, indurated ulcer of syphilis.
The primary ulcer of LGV is small, painless, and transient, often going unnoticed before the development of painful inguinal lymphadenopathy (buboes).
A cancerous ulcer would be chronic and persistent, with firm, indurated borders, and would not resolve spontaneously or respond to penicillin like a chancre.
