Secondary oral syphilis presenting as a tumor-like lesion on the lower lip.

This study presents a case of atypical manifestation of secondary syphilis. Diagnosis was initiated prompted by the patient's complaint of a lower lip lesion, present for three months, resembling a malignant neoplasm. The lesion, a 3 cm (diameter) ulcerated nodule, arising from conjunctive tissue, raised concern. However, further physical examination revealed additional clinical features, including cervical micropolyadenopathy and erythematous skin lesions, prompting a reevaluation of the diagnosis, most likely secondary syphilis. These findings led to a serological investigation, which, ultimately, confirmed the diagnosis of syphilis. The case underscores the importance of recognizing syphilis as a formidable imitator, posing challenges in establishing differential diagnoses of mucocutaneous diseases.