[A case of pulmonary actinomycosis radiologically mimicking a lung cancer].

A 59-year-old male clerk consulted in general practitioner due to cough and hemoptysis. A mass shadow was pointed out in the left upper lung field on a chest radiograph. Patient was referred to our hospital for further treatment. Any definitive daiagnosis could not be made after examinations including sputum culture, cytology and TBLB. Because a lung cancer was strongly suspected, an exploratory thoracotomy was performed. Actinomyces was detected by pathological study of excised specimen, with no evidence of cancer. ABPC was administered for two months postoperatively. The patient is doing well without recurrence of actinomycosis 2.5 years after the surgery. Pulmonary actinomycosis presenting a mass shadow on a radiograph may mimick a pulmonary tumor, especially a lung cancer. Pulmonary actinomycosis should be considered in a differential diagnosis of pulmonary lesion thought to be malignant.