272 Chapter 17 Figure 3. Schematic drawing of normal secondary lobular anatomy of the lung. The bronchiole is accompanied by the pulmonary artery (blue). The veins (red) are located in lobular septa. Note the small holes focally in the septa (green arrow head). Note: I) In AIS the tumor cells respect the pre-existing structures and II) Tumor cells may cross the interlobular septa through focal alveolar connections (green arrow head) III) The secondary alveolar lobules have greater and bigger connections with neighboring lobules at their central part. AIS and size Finally, AIS has been defined as a non-invasive adenocarcinoma of a diameter of 3 cm or less. In chapter 16 we describe 4 cases with tumors of diameters larger than 7 cm, even much larger, up to 18 cm, that showed on histology a pure, non-invasive lepidic pattern similar to Noguchi type A10. In addition, we examined in one patient practically the whole lobe with over 300 formalin fixed paraffin embedded blocks and could beside the Noguchy type A pattern not find an invasive focus, rendering an underdiagnosis of AIS due to sampling highly unlikely. Incidental cases with AIS larger 3 cm have also been described. Therefore, we propose that the upper limit of 3 cm for non-invasive non-mucinous adenocarcinoma can be omitted. Limitations of the studies in this thesis A disadvantage of the current studies is that most of them were performed in a retrospective way. Furthermore, verifying the hypotheses with the iatrogenic collapsed
RkJQdWJsaXNoZXIy MTk4NDMw