Subsolid Lung Nodule Classification: A CT Criterion for Improving Interobserver Agreement

Abstract

Purpose To evaluate an objective computed tomographic (CT) criterion for distinguishing between part-solid (PS) and nonsolid (NS) lung nodules. Materials and Methods This study received institutional review board approval, and patients gave informed consent. Preoperative CT studies in all patients who underwent surgery for subsolid nodules between 2008 and 2015 were first reviewed by two senior radiologists, who subjectively classified the nodules as PS or NS. A second reading performed 1 month later used predefined classification criteria and involved a third senior radiologist as well as three junior radiologists. Subsolid nodules were classified as PS if a solid portion was detectable in the mediastinal window setting (nonmeasurable, < 50%, or > 50% of the entire nodule) and were otherwise classified as NS (subclassified as pure or heterogeneous). Interreader agreement was assessed with κ statistics and the intraclass correlation coefficient (ICC). Results A total of 99 nodules measuring a median of 20 mm (range, 5-47 mm) in lung window CT images were analyzed. Senior radiologist agreement on the PS/NS distinction increased from moderate (κ = 0.54; 95% confidence interval [CI]: 0.37, 0.71) to excellent (κ = 0.89; 95% CI: 0.80, 0.98) between the first and second readings. At the second readings, agreement among senior and junior radiologists was excellent for PS/NS distinction (ICC = 0.87; 95% CI: 0.83, 0.90) and for subcategorization (ICC = 0.82; 95% CI: 0.77, 0.87). When a solid portion was measurable in the mediastinal window, the specificity for adenocarcinoma invasiveness ranged from 86% to 96%. Conclusion Detection of a solid portion in the mediastinal window setting allows subsolid nodules to be classified as PS with excellent interreader agreement. If the solid portion is measurable, the specificity for adenocarcinoma invasiveness is high. RSNA, 2017 Online supplemental material is available for this article.

Diagnosis of Invasive Lung Adenocarcinoma Based on Chest CT Radiomic Features of Part-Solid Pulmonary Nodules: A Multicenter Study

“…Although radiologists are able to assess the invasive probability of PSNs using semantic or morphologic CT features (eg, diameter, solid proportion) and medical history in clinical practice, this method is limited by subjectivity and creates a work burden (10)(11)(12). Automated volumetric analysis facilitates the quantification of the nodule volume and mean density with higher repeatability than manual measurement (13).…”

Value of TSCT Features for Differentiating Preinvasive and Minimally Invasive Adenocarcinoma From Invasive Adenocarcinoma Presenting as Subsolid Nodules Smaller Than 3 cm

“…The correlations between pathological findings and thinsection CT features of SSNs have been evaluated in numerous studies and have provided new opportunities for predicting the histologic subtype of adenocarcinoma (22). The qualitative/ semiquantative/quantative measurements have been applied to distinguish preinvasive and invasive lesions (22À27).…”

Long-Term Active Surveillance of Screening Detected Subsolid Nodules is a Safe Strategy to Reduce Overtreatment

“…[2][3][4][5] Such overdiagnosis and overtreatment are especially seen in slow-growing lung adenocarcinomas that are mostly represented by subsolid nodules (SSNs). [6][7][8][9][10] Retrospective studies assessing precursor lesions of interval cancers and post-screen cancers showed that SSNs were visible at the tumor sites years before tumor diagnosis. 11 Such retrospective evidence prompted more conservative algorithms in the most recent guidelines.…”