'Real' Tumor-Spread Through Air Spaces of Lung Adenocarcinoma Presented Intrapulmonary Metastases Through Bronchiole Air Spaces: A Case Report

Here, we report a rare case of lung adenocarcinoma with intrapulmonary metastases that have “spread through air spaces” (STAS) by means of the alveoli and bronchioles. The peripheral intrapulmonary metastases were exhibiting pure ground-glass nodules along the bronchioles on computed tomography. The primary pathologic diagnosis was micropapillary adenocarcinoma with prominent tumor STAS. Histopathologic examination revealed that the cancer cells in the bronchioles around the primary tumor revealed micropapillary clusters on the mucosal surface or in the air spaces and reached peripheral intrapulmonary metastatic nodules. Notably, no vascular and stromal invasion was observed. The pathologic findings suggest that cancer cells are viable in the airspace of the bronchioles and alveoli and may support the significance of STAS as a pattern of airborne metastasis.