Role of computed tomography in the diagnosis of solitary pulmonary nodule with solid component: a narrative review

Objective: The aim of this paper is reviewing the role of computed tomography (CT) in the diagnosis and management of solitary pulmonary nodules (SPNs) with solid component, namely solid and partially solid nodules. Background: The topic is of great interest because the number of pulmonary nodules identified has dramatically raised over time, as a consequence of the increased use of CT in medical care and the diffusion of screening programs. Methods: MEDLINE and PubMed search was conducted from 2000 through June 2021 using as keywords: "lung cancer", "computed tomography", pulmonary nodule", "solid nodule" and "partially solid nodule". Conclusion: Size and growth rate assessed by baseline CT and eventual control are the main determinant for management according to guidelines issued by all thoracic society. Most recent guidelines on this topic are summarized. In addition, CT morphological aspects may help the characterization of a nodule, in terms of benignity/malignancy and therefore suggesting a closer or longer follow-up (FUP) or a more invasive diagnostic procedure. Nowadays and in the near future, artificial intelligence (AI) algorithms have the potential to assist radiologists in the difficult task of detecting but also in diagnosing pulmonary nodules, in terms of lesion's volumetry and characterization. This narrative review provides an overview on the role of CT in the evaluation of SPNs with solid component, mainly based on size and growth rate but also on morphological benign and/or malignant features that a radiologist should recognized in order to allow an early diagnosis and a prompt intervention in case of a malignancy and to avoid unnecessary CT FUP or invasive for nodules.