Mediastinal Mass, Cancer, or Infection, Atypical Paraesophageal Actinomycosis Infection, Clinical and Surgical Approach.

Actinomyces israelii (AI) is a Gram-positive, rod-shaped bacterium that lives commensally on and within humans as a typical colonizer within the gastrointestinal tract, including the mouth. As an opportunistic pathogen, infection often results from tissue injury or breach of the mucosal barrier (ie, during various dental or GI procedures, aspiration, or specific pathologies such as diverticulitis). Symptoms generally present slowly as a non-tender, indurated mass that evolves into multiple abscesses, fistulae, or draining sinus tracts without regard for anatomical barriers, including fascial planes or lymphatic drainage. However, it may also present as an acute suppurative infection with pain and rapid progression to abscess formation.