[Thoracic actinomycosis: report of a case].

Actinomycosis is a disease produced by bacteria of the genus Actinomyces. The thoracic form represents 30% of the cases. Signs and symptoms are generally unspecific. A previously healthy 11 year old girl was admitted with a chest mass of a month of evolution associated with fever, hyporexia and weight loss. Thoracic actinomycosis was diagnosed with the isolation of Actinomyces meyeri in the mass drainage. She received antibiotic treatment for a year with complete resolution. Although rare, it should be taken into account as a differential diagnosis in long evolution thoracic tumor affecting the general condition. The microbiologist must be warned about the suspected diagnosis because it is difficult to find it in routinely used culture media.