Management of Nodules Attached to the Costal Pleura at Low-Dose CT Screening for Lung Cancer.

Background: Pulmonary nodule features have been used to differentiate benign from malignant nodules. Purpose: To determine the frequency of solid noncalcified nodules attached to the costal pleura (CP-NCNs) at baseline low-dose CT and to identify key features of benignity. Materials and Methods: A retrospective review was performed of baseline low-dose CT scans obtained in 8730 participants in the Mount Sinai Early Lung and Cardiac Action Program screening cohort between 1992 and 2019. Participants with one or more solid CP-NCNs between 3.0 mm and 30.0 mm in average diameter were included. For each CP-NCN, the size, location, shape (lentiform, oval, or semicircular [LOS]; triangular; polygonal; round; or irregular), margin (smooth or nonsmooth), and attachment to the costal pleura (broad or narrow) were documented. The manifestation of emphysema and fibrosis within a 10-mm radius of the CP-NCN was determined. Multivariable logistic regression analysis, with synthetic minority oversampling techniques, was used. Results: The 569 eligible participants (average age, 62 years 6 9 [standard deviation]; 343 women) had 943 solid CP-NCNs, of which 934 (99.0%) were benign and nine (1.0%) were malignant. Multivariable analysis showed that five shapes could be consolidated into three (LOS and/or triangular, round and/or polygonal, and irregular shape); pleural attachment was not a significant independent predictor (odds ratio, 1.24; P =.70); and interaction terms of size with shape (odds ratio, 0.73; P =.005) and margin were significant (odds ratio, 0.80; P =.001). All 603 CP-NCNs less than 10.0 mm with LOS or triangular shapes and smooth margins were benign. Conclusion: All baseline noncalcified solid nodules attached to the costal pleura less than 10.0 mm in average diameter with lentiform, oval, semicircular, or triangular shapes and smooth margins were benign; thus, for these nodules, an annual repeat scan in 1 year, rather than a more immediate work-up, is recommended. (C) RSNA, 2020.