Abstract
We describe a case of actinomycosis of the gallbladder mimicking carcinoma. Sonography showed a hypoechoic mass replacing gallbladder lumen and engulfing a stone; contrast-enhanced computed tomography showed a heterogeneously enhanced thickened gallbladder wall with subtle, disrupted luminal surface enhancement, which formed a mass. As a result of the clinical and radiologic presentation, our impression was of gallbladder carcinoma. Actinomycosis should be included in the differential diagnosis when sonography and computed tomography findings show a mass engulfing the stone in the gallbladder and extensive pericholecystic infiltration with extension to neighboring abdominal wall muscle.