If infected with syphilis, a hard chancre can usually appear 2-3 weeks after infection. The chancre is highly contagious and can last for 3-4 weeks or longer in untreated cases, and usually resolves after 1-2 weeks in treated patients. The chancre appears as small red spots on the external genitalia, mostly on the penis, glans, prepuce and tether in men, and on the labia, perineum and uterine opening in women. The erythema becomes necrotic and can form a round or oval painless ulcer of 1-2 cm in diameter, which is usually painless and therefore difficult to detect. After the chancre subsides, a dark red scar or discoloration of the skin may remain. 1-2 weeks after the appearance of the chancre, enlarged lymph nodes may be seen in the groin and near the affected area.