Fig. 2

Pathological diagnosis of STAS. A Diagnosis of STAS by hematoxylin and eosin staining on paraffin sections. STAS (arrow) was located in the alveolar lumen outside the margin of the main tumor (black dashed line). B Immunohistochemical identification of STAS. STAS (arrow, TTF-1 positive) was located in the alveolar lumen outside the margin of the main tumor (black dashed line). C Immunohistochemistry identified non-tumor cells, mainly tumor-associated macrophages (arrows, CD68 positive). STAS: tumor spread through air spaces