Background: Visceral pleural invasion (VPI) had been demonstrated as an aggressive sign in non-small cell lung cancers (NSCLC). However, its incidence and clinical relevance in early lung cancer showing ground glass nodules (GGNs) has not been clarified.
Methods: All consecutive surgically treated patients with solitary GGNs between 2009 and 2013 were reviewed retrospectively. Inclusion criteria were defined as lesions ≤3 cm with pleura abutting on computed tomography (CT) scan and pathologically confirmed NSCLC.
Results: Out of 156 enrolled patients, 38 had pathologically confirmed VPI. The incidence of VPI was 41.5% (27/65) if the tumor diameter was larger than 2.0 cm and 14.3% (13/91) if diameter was smaller than 2.0 cm (P<0.001). Further, the incidence was 17.4% (12/69) in pure GGNs and 32.2% (28/87) in part-solid GGNs (P=0.040). The tumor size and the nodule nodule-pleural relationship were significant predictors of positive VPI. In cases with pleural indentation, attachment, and closeness, the incidence was 38.1%, 25.5%, and 5.3%, respectively (P=0.001). All cases were PL0 and PL1, with no PL2 cases observed.
Conclusions: Although VPI was visible in both pure/mix GGNs, it was more common in larger (>2 cm) GGNs. The radiographic findings of nodule abutment or a pleural tag did not reliably predict or exclude VPI. In patients with GGNs, a low rate of PL2 invasion may be observed.
Keywords: Non-small cell lung cancer (NSCLC); ground-glass nodules (GGN); visceral pleura invasion.