174 Chapter 14 Abstract Introduction For resected non-small cell lung cancer specimens, recognizing non-invasive growth patterns is necessary to correctly estimate their T-stage and to distinguish between invasive and non-invasive adenocarcinoma, as prognosis varies greatly. In particular, after resection due to iatrogenic collapse, this distinction can be difficult. The aim of this study is to investigate the complex morphology of non-mucinous non-invasive patterns of adenocarcinoma in situ (AIS) in resection specimen with iatrogenic collapse, and to relate this to follow-up. Material and methods The effects of iatrogenic collapse on the morphology of collapsed AIS were examined on a mathematical model, and subsequently re-examined with a revised classification using also cytokeratin 7 and elastin as additional stainings in two independent retrospective cohorts of primary pulmonary small (≤3 cm) adenocarcinomas resection specimen with available follow-up information. Results The morphometrical model demonstrated that wrinkling of alveolar walls occurs during iatrogenic collapse, leading to significant increase in tumour cell heights in maximal collapse areas. Out of a total of 70 resection specimen 10 were (re)classified as iatrogenic collapsed AIS. Patients with AIS showed a 100% recurrence-free survival after a mean follow-up time of 69.5 months. Conclusions Iatrogenic collapsed AIS forms a morphologic complex, wrinkled pattern with in the cytokeratin 7 a regular pattern and in the elastin staining a preserved elastin framework. A classification with refined criteria facilitates the diagnosis of iatrogenic collapsed AIS.
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