238 Chapter 16 was made based on the available anonymous pathology reports, which mentioned lepidic or (micro)papillary growth. These cases were considered possible non-invasive adenocarcinomas. H&E-stained slides and paraffin blocks of all adenocarcinoma cases were retrieved from the various pathology departments. After review of the H&E slides (HB, ET, both with over 30 years of experience in pulmonary pathology), a representative paraffin block from the putative non-invasive cases was selected. Areas of suspected invasion were selected when choosing a representative block. Additional staining, including EvG and immunohistochemical stainings for CK7, TTF1, and p40 were performed. The presence of TTF-1 and absence of p40 confirmed the diagnosis of adenocarcinoma. Adenocarcinoma in-situ (AIS) was defined as a monolayer of tumor cells on the alveolar wall with or without collapse, using H&E, EvG, and CK7, as was recently described343. For every potential pulmonary non-mucinous adenocarcinoma in-situ case, an age, gender, and date (by year) of surgical resection matched invasive control was selected from the same institute. Pre-operative CT imaging, obtained in anonymous form on CD-ROM from different radiology departments, were reviewed by a radiologist (OM) to assess tumor diameter, presence of ground glass opacities or semi-solid areas/consolidations and solid areas. If present the diameter of solid components in ground glass areas was estimated. We categorized three groups of tumor morphology: i) completely solid mass, ii) mass with partial ground glass as well as solid component(s) (subsolid), and iii) more diffuse consolidation with varying amounts of ground glass and solid components (also called ‘pneumonia-like’). The correlation between the radiology findings and histology was evaluated using these three categories. Due to the retrospective nature of the study, only selective blocks were obtained for diagnostic purposes, rather than including the entire tumor or a significant portion of it. Radiological and pathological examination of the retrospective study cases was performed blinded for the other diagnostic technique and for follow-up. Comprehensive follow-up data of all selected cases were collected from various hospitals, including cases that had been referred to other centers. Data retrieval of the T3N0 cohort was approved by the IKNL privacy review board and performed in accordance with the regulations of the Central Committee on Research involving Human Subjects as well as the ethical committee of PALGA (IKNL No K14.250; PALGA lzv1142/2019-4-A2). The study was conducted according to the criteria set by the 1964 Declaration of Helsinki and later Amendments and in accordance with the Strengthening the Reporting of Observational Studies in Epidemiology Statement (STROBE) guidelines. Due to the retrospective nature of the study, approval by the ethical committee in Milan was waived. No identifying details of the patients were mentioned in this study, all information were anonymized, and the images included may not be identified persons.
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