A Case Report of Syphilis That Was Difficult to Distinguish From Penile Carcinoma.

A 43-year-old man presented with penile induration and lymphadenopathy. Computed tomography revealed multiple enlarged lymph nodes (LNs). Penile cancer was suspected, and a LN biopsy was performed. Histopathological examination revealed inflammation and fibrosis, with no findings indicating malignancy. Serological examination confirmed syphilis and treatment with amoxicillin was initiated. Thereafter, swelling in the LNs improved quickly. Penile cancer is usually suspected in the presence of penile induration. However, syphilis can also present with similar symptoms. To distinguish between syphilis and penile cancer, the patient's history, results of physical examination, and presence of tumor and infectious markers should be considered.