A case of secondary syphilis involving tonsil, pulmonary, and multiple lymph nodes: 18F-FDG PET/CT findings.

A 50-year-old man with general fatigue and weight loss underwent FDG PET/CT scan to detect possible occult malignancy. The images revealed abnormal FDG activity in the tonsils, right lung, and in the cervical, axillary, and inguinal lymph nodes. Lymphoma was initially suspected. However, pathologic examination after cervical lymph node biopsy revealed only reactive hyperplasia. Further examinations including serologic tests led to a diagnosis of secondary syphilis. A follow-up PET/CT scan after a 6-month benzylpenicillin therapy showed significant interval improvement.