A 4-year-old, male French Brittany weighing 18 kg was presented for continuous disorexia associated with a large palpable mass in the cranial abdomen. Radiographic and ultrasonographic examination showed the presence of a mass close to the gastric wall. Percutaneous needle aspiration of the mass revealed pyogranulomatous inflammation. An exploratory laparotomy was performed in order to remove the mass. Actinomiycotic mycetoma was revealed after surgery by positive culture. After a three months antibiotic therapy, nine months follow up showed complete remission.

Key words: Actinomycetoma, Dog, Gastric wall, Mass