Tumor spread through air spaces

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Tumor spread through air spaces (STAS) is a relatively recently recognized pattern of invasion in lung adenocarcinoma. According to the 2015 WHO classification, STAS is defined as “micropapillary clusters, solid nests, or single cells spreading within air spaces beyond the edge of the main tumor” . Presence of STAS is considered a significant risk factor of recurrence in small lung adenocarcinomas treated with limited resection.