Pulmonary actinomycosis: the great masquerader.

Actinomycosis is a rare but treatable disease. Thoracic manifestations are varied and can mimic malignancy or tuberculosis. We report the case of a 54-year-old man who presented with a persistent cough and radiological evidence of right upper lobe lung mass. Conventional computed tomography guided biopsy and bronchoscopy proved to be non-diagnostic. Thoracotomy and histopathologic examination of the tissue confirmed actinomycosis infection. Excellent clinical and radiologic responses were noted following treatment with penicillin V. Despite a high clinical suspicion, the diagnosis can prove to be challenging.