Case 133. Syphilis, primary (45 y-o M)
Biopsy from a painless penile ulcer
Key words : Treponema pallidum, primary syphilis, hard chancre
sexually transmitted infection
A deep but painless ulcer (hard chancre) is formed in the prepuce (gross findings).   Reactive squamous epithelial thickening with downward elongation is noted, in association with marked lymphoplasmacytic infiltration (HE, low power).
In the dermis, plasma cell infiltration predominates, and endothelial cells are swollen (HE, high power).   Highly coiled spiral microbes are identified among the squamous epithelium (Warthin-Starry's silver). This silver method is technically difficult, and the reproducibility is not satisfactory.
Highly coiled spiral microbes are easily demonstrated by immunostaining using a specific antiserum against Treponema pallidum. The spirochetae are localized in the intercellular space.