[A case of pancreatic actinomycosis diagnosed by EUS-FNA].

A 60-year-old male patient had alcoholic chronic pancreatitis. Three months prior, he had undergone an exchange of pancreatic duct stents. In December 201X-1, magnetic resonance imaging and computed tomography (CT) scan results showed a caput pancreatic mass and common bile duct dilatation. We considered that it was because of chronic pancreatitis and decided to follow up by imaging studies. Further, in March 201X, a CT scan result revealed worsening of the mass and bile duct dilation. We assessed the mass by endoscopic ultrasound and fine-needle aspiration. Histological findings revealed to an interstitial tissue infiltrated by several neutrophils and plasma cells and abscess-forming inflammation like sulfur granule. The mass was improved by antibiotic administration for 6 months.