Preface on “pulmonary nodules special issue for lung cancer”

The incidence of small pulmonary nodules (SPNs) is increasing as a result of the widespread use of multislice spiral computed tomography (CT) and the low-dose helical CT screening for lung cancer (1). A pulmonary nodule is definite as a well or poorly-circumscribed, approximately spherical, radiographic opacity less than or equal to 30mm in diameter that is completely surrounded by aerated lung and is not associated with atelectasis, hilar enlargement, or pleural effusion, which can be divided into solid and sub-solid nodules, with the latter group further subdivided between pure ground-glass opacity (GGO) and part-solid nodules (2).