Figure 3

Microscopic examination of the BC of the lung. (A) Low power view showed a solid and sheet-like proliferation of relatively uniform and small to medium-sized atypical epithelial cells having hyperchromatic nuclei and scant eosinophilic cytoplasm, often arranged in an alveolar fashion with peripheral palisading. However, rosettes structures were absent. Apparent keratinization, intercellular bridge, or glandular differentiation was also not evident (H&E stains). Bar = 100 μm. (B) On high-power view, mitotic counts (arrowheads) were high (more than 15 per 2 mm²) (H&E stains). Bar = 25 μm. (C) Although foci of comedo-type tumor necrosis were not recognized within the cancer nests and the central cavity, the cancer-cavity junction contained coagulative necrosis of pre-existing alveolar wall (inset) (H&E stains). Bar = 1 mm.