Actinomyces naeslundii, acute cholecystitis, and carcinoma of the gallbladder.

This report describes the first case of biliary actinomycosis associated with an adenocarcinoma of the gallbladder. Actinomyces naeslundii was encountered as a pure isolate after a precise and careful identification. Although, in diagnosis, cancer and actinomycosis are often confused, the simultaneous occurrence of actinomycosis in cancer lesions can happen. This case illustrates the diagnostic challenge of actinomycosis.