192 Chapter 14 Figure 12. Examples of CK7 IHC in normal lung parenchyma (A), normal expanded alveoli, collapsed normal parenchyma (B) and collapsed AIS (C, D). The red line has a length of 200 μm, equivalent to the diameter of a normal air-filled alveolar space as shown in A. In the collapsed normal lung parenchyma (B), up to 12 alveolar septa were counted along a line of 200 μm. In pulmonary adenocarcinoma with lepidic growth approximately 4-5 cross sections of alveolar walls lined with tumour cells fit into a length of 200 μm. This model apparently has two implications for lung morphology. Firstly, due to iatrogenic collapse, an alveolus shrinks to less surface area than in-vivo. As the alveolar wall membrane surface will not decrease during iatrogenic collapse, the only option for the alveolar walls is to spatially fold (Figure 1, 12 and the grape as an analogous example in Figure 3). Secondly, the folding of the lining epithelial cells may result in sideways tension on these cells. When the collapse is at its maximum, all of the tumour cells will be subjected to maximal compression. However, if the collapse is less prominent, then the pressure on the tumour cells may be lower. As tumour cells typically make contact with the basement membrane on the basal side and are surrounded by neighbouring tumour
RkJQdWJsaXNoZXIy MTk4NDMw