Malignant transformation of pulmonary bronchiolar adenoma into mucinous adenocarcinoma: A case report

Figure 2 Hematoxylin and eosin staining of the whole tumor. A: The tumor consisted of two general areas (×100): A bronchiole adenoma (BA) (yellow dotted line) area and a mucinous adenocarcinoma (black dotted line) area; B and C: The BA area consisted of a bilayered structure of luminal cells and basal cells that were arranged in glandular, papillary, and flat structures (B: ×100, and C: ×200); D: At high magnification (×400), basal cells (white arrows), ciliated cells (orange arrows) or cubic/Low columnar cells and locally abundant mucinous cells (black arrow), without significant atypia or pathological mitosis, were evident in the luminal epithelium. BA: Bronchiole adenoma; MA: Mucinous adenocarcinoma.