The Silent Mimic: Actinomyces and the Enigmatic Gastric Ulcer

A 63-year-old woman presented with hematemesis, melena, and epigastric pain. Laboratory tests revealed severe anaemia, hypoalbuminemia, and elevated cancer antigen 19-9 (CA 19-9). Gastroscopy revealed oesophageal erosions and a gastric ulcer with a wide, black-coloured base on a polypoid lesion, along with small erosions. Histopathological findings showed filamentous and rod-like bacteria, consistent with Actinomyces, in gastroscopic biopsies. The patient was then treated with high-dose intravenous penicillin G. <b>Conclusion:</b> This case highlights the diagnostic challenges of gastric actinomycosis, which can be mistaken for peptic ulcers or malignancy. Clinicians should consider gastric actinomycosis, especially in immunocompromised patients, when imaging or endoscopy reveals a submucosal lesion or ulcer.