Genetic and clinicopathologic characteristics of lung adenocarcinoma with tumor spread through air spaces

Objective: The World Health Organization Classification of Lung Tumors considers “Spread Through Air Spaces (STAS)” as a form of invasion in lung adenocarcinoma. However, its existence as an independent pathologic entity rather than an artifact caused by spreading through a knife surface is still controversial. Therefore, we performed comprehensive analyses on the genetic and clinicopathologic characteristics of lung adenocarcinoma with STAS. Materials and Methods: A total of 316 surgically resected lung adenocarcinoma cases were analyzed retrospectively. Detailed analyses were performed on clinical-histological-molecular features. Tumor STAS was defined as tumor cells within air spaces in the lung parenchyma beyond the edge of the main tumor. Results: STAS was observed in 160 cases (50.6%). STAS was significantly related to lymphovascular invasion, lymph node metastasis, higher stage, and high-grade histologic subtype. STAS was frequently found in tumors with wild-type EGFR or ALK-rearrangement. Logistic regression analysis showed that STAS was significantly associated with absence of lepidic component, presence of micropapillary component, cribriform predominant type, lymphovascular invasion, and wild-type EGFR. Multivariate survival analysis demonstrated that STAS was independently associated with shorter recurrence-free survival. STAS was also associated with recurrences to extrathoracic sites as well as intrathoracic sites. Conclusion: STAS is associated with certain pathological and molecular subtypes. STAS might be a parameter for tumor aggressiveness in that it is strongly associated with poor prognostic factors and recurrence, including to extrathoracic sites.