Tumor spread through air space, the clinical implications for T factor and effects on the disease recurrence and prognosis

The findings for the tumor spread through air space (STAS) in lung adenocarcinoma were reported by Kawakami et al. (1) and have attracted attention as unique clinical characteristics associated with a micropapillary pattern and nodal metastasis (1). In 2011, the International Association for the Study of Lung Cancer (IASLC), the American Thoracic Society (ATS), and the European Respiratory Society (ERS) revised the classification of lung adenocarcinoma to include the novel findings of molecular pathology as well as the correlation with clinical outcomes (2). STAS was clearly recognized as a novel invasive morphology defined as a micropapillary clusters, solid nests, or single cells beyond the edge of the tumor into air spaces in the surrounding lung parenchyma (3). The latest WHO Classification of Tumors of The Lung, Pleura, Thymus and Heart 4th Edition in 2015 (4) basically follow the IASLC/ATS/ERS classification.