Introduction: Syphilis is a sexually transmitted disease identified as a global health problem. Its gastric, esophageal and/or intestinal involvement occurs in around 1% of cases. The descriptions of endoscopic lesions and histopathological biopsies are similar to other more prevalent diseases, such as mucosal infiltrative tumors, lymphomas related to Helicobacter pylori infection, Crohn's disease and adenocarcinomas. Objective: To report the case of an adult male patient with imaging tests mimicking gastric neoplasia, which were, in fact, lesions suspected of syphilis, its resolution and management. Case report: A 39-year-old man sought care because of severe epigastric pain related to the postprandial period and prolonged fasting, without improvement with medication. He reported weight loss and episodes of dark-colored vomiting. On physical examination, pain on deep palpation in the epigastric region without palpable masses and peristalsis was present. An endoscopy was performed, the report of which indicated endoscopic gastritis with marked flat erosions in the antrum, with eroded, bloody, intensely friable mucosa. Also, a biopsy of the mucosa was performed, with a histopathological report resulting in a large plasma cell infiltrate, with VDRL/FTA-Abs being ordered because of the prevalence of differential diagnoses. The patient was diagnosed with syphilis and was treated with benzathine penicillin 2,400,000 IU IM in three doses, one every seven days, for a total of 7,200,000 IU. He returned in six months for reevaluation. Conclusion: Although this is a rare occurrence of the disease, one should always be aware of possible differential diagnoses to avoid unnecessary surgical interventions and procedures.