A Case of Pulmonary Actinomycosis that was Difficult to Differentiate from Primary Lung Cancer Preoperatively

Abstract

A 67-year-old woman, who presented with cough and hemoptysis, was followed up for three months, but the symptoms worsened. A chest computed tomography revealed a solid irregular mass measuring 37 mm in diameter in the lower lobe of the right lung. While a bronchoscopy at another hospital did not provide a definitive diagnosis, the mass was suspected as primary lung cancer. A repeat bronchoscopy at our hospital again failed to reveal the diagnosis and no specific bacteria were isolated. The lung lesion grew to the diameter of 42 mm by six months and a slight increase of the serum sialyl Lewis X-i antigen level was observed. Therefore, video-assisted thoracoscopic surgery was performed for diagnosis and treatment. Right lower lobectomy was performed and an intraoperative rapid diagnosis confirmed an inflammatory lesion. Subsequent histopathological examination revealed sulfur granules with mycelia arranged in a radiating pattern, suggestive of the diagnosis of pulmonary actinomycosis. There has been no recurrence for 18 months after the operation, despite no additional antibiotic therapy. It remains difficult to diagnose pulmonary actinomycosis by non-invasive examinations. Surgery should be adopted to differentiate lung cancer from an inflammatory mass, including pulmonary actinomycosis.