Pleural Tags on CT Scans to Predict Visceral Pleural Invasion of Non-Small Cell Lung Cancer That Does Not Abut the Pleura

To evaluate the association of pleural tags with visceral pleural invasion of non-small cell lung cancer (NSCLC) that does not abut the pleural surface. This retrospective study was approved by the institutional review board. Informed consent was waived. The study of NSCLC that does not abut the pleura in 141 patients (44 patients [31.2%] with visceral pleural invasion proved by pathologic analysis and 97 patients [68.8%] without pleural invasion) was conducted at a single tertiary center. The pleural tags were classified into three types (type 1, one or more linear pleural tag; type 2, one or more linear pleural tag with soft tissue component at the pleural end; and type 3, one or more soft tissue cord-like pleural tag) and prioritized into types 3, 2, and 1 when more than one type was present. Diagnostic accuracy, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and positive likelihood ratio (LR) were calculated. In the absence of pleural tags, no pleural invasion was found. The presence of type 2 pleural tags was moderately associated with visceral pleural invasion with the following results: positive LR, 5.06; accuracy, 71%; sensitivity, 36.4%; specificity, 92.8%; PPV, 76.2%; and NPV, 69.6%. Type 1 pleural tags provided weak evidence to rule out visceral pleural invasion (positive LR, 0.38). Type 3 pleural tags indicated minimal increase in the likelihood of visceral pleural invasion (positive LR, 1.68). Type 2 pleural tags on conventional CT images can increase the accuracy of early diagnosis of visceral pleural invasion by NSCLC that does not abut the pleura.