This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Skin
A young long-distance lorry driver presents to the clinician with a painless penile ulcer 9 days after sexual intercourse with a professional sex worker. What is the likely diagnosis? 
Select and explain. 
A. Herpes Genitalis, B. Chancre, C. Chancroid, D. Traumatic ulcer
B: Chancre
Answer: B: Chancre 
Explanation: Chancre is a sign of primary syphilis which occurs within 2-3 weeks of initial inoculation. The lesion is characteristically painless. It is initially a dull red macule which becomes papular and fuher erodes to become an indurated ulcer called chancre. These lesions resolves spontaneously within 2 months if not treated. Herpes, Chancroid and Traumatic ulcer are painful lesions. Ref: Davidson's Principles and Practice of Medicine, By Sir Stanley Davidson, Christopher Haslett, 2002, Page 97.