Pulmonary actinomycosis is a rare disease frequently misdiagnosed, even by experienced clinicians, as primary or metastatic lung cancer or as other more conventional lung infections. It is often an unexpected disease that is basically detected only on cytological/histological examination. A case involving a patient who presented with a mass in the bronchial stump (of a previous pulmonary lobectomy) is described. Despite a strong suspicion of recurrent lung cancer, positron emission tomography confirmed a diagnosis of a suture-related bronchial actinomycosis.