Actinomycosis: an often forgotten diagnosis.

We report a case of actinomycosis presenting as a chest wall mass in a 35 year-old man. Thoracic actinomycosis poses a diagnostic challenge to clinicians not only because it is uncommon and often forgotten, but also because culture of the causative microbes is technically difficult. The classic microscopic appearance of this Gram-positive bacteria associated with surrounding sulfur granules often forms the basis of diagnosis.