Small lung nodule is a common problem in pulmonary practice. The definition of a classical solitary pulmonary nodule is a single, spherical, well-circumscribed, radiographic opacity less than or equal to 30 mm in diameter that is completely surrounded by aerated lung and is not associated with atelectasis, hilar enlargement, or pleural effusion. Ideally, the goal of diagnosis and management is to promptly bring to surgery all patients with operable malignant nodules while avoiding unnecessary thoracotomy in patients with benign disease. In fact, causes of solitary pulmonary nodules can be benign or malignant. In order to diagnose causes of solitary pulmonary nodules, we can use many different methods, including clinical symptoms, radiographic features, liquid biopsy, bronchoscopy, CT-guided fine-needle aspiration biopsy and surgery. Each method has its own value. It is very meaningful if we can diagnose these causes early. Based on these results, doctors can determine the strategy to manage disease.
