Syphilitic orchitis is a rare manifestation of gumma in tertiary syphilis, microscopically typically characterized by multiple discrete granulomas with central necrosis and peripheral fibrosis. We report a case of syphilitic orchitis mimicking a testicular tumor with atypical histological features.
A 33-year-old clinically occult HIV-infected man had a testicular tumor. A radical orchiectomy was performed, and a histological examination showed an acute and chronic interstitial inflammatory lesion as well as spindle cell proliferation, without typical gumma formation, necessitating the differential diagnosis having to be made from a panel of etiological factors. Syphilitic orchitis was confirmed by both an immunohistochemical study and PCR testing for the Treponema pallidum DNA polymerase I gene using paraffin-embedded tissues. However, serology tests, including both the Venereal Disease Research Laboratory (VDRL) test and Treponema pallidum partical agglutination (TTPA), demonstrated false-negative results.