Diagnostic management of solitary pulmonary nodule

Solitary pulmonary nodule (SPN) is defined as a single, approximately round and well-circumscribed radiographic opacity ƒ3 cm in diameter which is completely surrounded by normal aerated lung parenchyma, without other abnormalities such as lymph node enlargement, atelectasis or pleural effusion [1]. The diagnosis of an SPN is a very common clinical problem and several pathological processes, both benign and malignant, may determine a solitary nodular lesion in the lung (table 1) [2]. Optimal management of SPN should allow the resection of all malignant nodules without delay and avoid useless surgery of benign nodules. How to reach this goal is an age old problem [3] and still remains today. Despite huge technological advancements in this diagnostic field, no widely accepted evidence-based guidelines completely address the approach to SPN [4]. In the last few years some new developments have changed the concept of managing SPN [5]. The widespread use of computed tomography (CT), the introduction of spiral and multi-detector row CT and the performance of CT-based screening programmes have greatly increased the identification of small subcentimetric nodules. The results from lung cancer screening projects show that noncalcified nodules are found in 20–50% of asymptomatic smokers or ex-smokers [6, 7]. The clinical meaning of these small lesions is different from the nodules detected by chest radiographs, generally .1 cm, for which the probability of malignancy is very high (64–82% for SPN .2 cm) [8] and for which the assumption that they should be considered malignant until proved otherwise is widely accepted. On the contrary, ,1% of nodules ,5 mm are malignant in patients without any previous history of cancer [9]. The likelihood of malignancy increases with the nodule size, being 0.2% for nodules ,3 mm, 0.9% for those 4–7 mm, 18% for those 8–20 mm [10] and y80% for nodules .20 mm [11]. The differences in epidemiology, clinical meaning and prognosis of subcentimetric nodules in comparison to nodules .1 cm prompt us to propose a separate specific management for these kinds of lesions. Scientific societies should probably also review the terminology for SPNs, taking into account that there should be a distinction between small and larger nodules when defining them (fig. 1). Furthermore, thanks to the diffusion of the CT scan, other new concepts concerning the morphology of SPNs have been introduced. The identification of nodules with a pure ground-glass attenuation pattern (ground-glass opacity) (fig. 1) or with a mixed solid component and ground-glass opacity, may have a different meaning in comparison with solid SPNs. In fact, nodules with ground-glass opacity pattern, even if they could represent conditions such as focal fibrosis, haemorrhage, inflammation and atypical adenomatous hyperplasia [12], are more likely to be malignant (70–100%) than solid