Spread Through Air Spaces (STAS): A New Pathologic Morphology in Lung Cancer

In 2015, the World Health Organization classification of lung cancer proposed the concept of spread through air spaces (STAS) as a new pattern of invasion in lung adenocarcinoma. The definition of STAS included one or more pathologic micropapillary clusters, solid nests or single cells beyond the edge of the tumor into air spaces in the surrounding lung parenchyma, and separation from the main tumor other than tumor islands. The roles of STAS has been investigated in many studies. The results indicated that STAS is associated with key clinical variables and the prognosis of patients both in lung adenocarcinoma, lung squamous cell carcinoma, small-cell lung cancer, and lung pleomorphic carcinoma. This mini review will be focused on the developments and perspectives of STAS in lung cancer.