119 Significance of loose tumor cells in pulmonary arteries adenocarcinoma and 38 cases with tumoral diameter > 3 cm). Of the remaining 142 cases, 48 had short or no accessible follow up information, for 2 cases cause of death was unknown and for 17 cases material was not available or insufficient. The remaining 75 cases from San Raffaele Scientific Institute were included for randomization. After randomization, 80 cases were included. Histological review of these cases was performed by 3 pathologists. For each case, one representative tumor block was selected and digitized. The digital images were uploaded on the collaborative platform for on-line teaching, training and quality assurance in pathology, Pathogate (https:// pathogate.net). After technical review of the cases, 10 were excluded, because of insufficient quality of the slide or out-of-focus areas after scanning. Therefore, 70 cases, 35 from each institute, were analyzed. Since in the original pathology reports subtyping of the adenocarcinomas was rarely reported, this was done by 2 pathologists in the categories adenocarcinoma in situ (AIS), lepidic predominant adenocarcinoma, low grade adenocarcinoma (acinar, papillary) with or without more than 10% high grade component and high-grade adenocarcinoma (micropapillary, solid). Cases with discrepancies (dominant pattern, presence of highgrade component) were reviewed, reaching consensus. Cytokeratin 7 (CK7) The immunohistochemical stain for CK7 (clone OVTL12/30 (Agilent/Dako (Glostrup, Denmark, catno. M701801)) was performed in a Roche/Ventana benchmark Ultra (Roche, Basel Switzerland) with 3µm tissue slides mounted on TOMO-glass slides (Roche, Basel, Switzerland). Antigen retrieval was applied with high pH-buffer CC1 (32 minutes at 100°C) and the antibody was diluted 1/100 (incubated for 32 minutes at 36°C) and detected with the Optiview DAB kit under standard conditions. Sections were dehydrated with ethanol 100%, cleared with Xylene and coverslipped with Tissue-Tek coverslip film on the Sakura coverslipper (Sakura Finetek Europe B.V, Alphen aan de Rijn, The Netherlands). Internal positive controls were pneumocytes and respiratory epithelial cells. Internal negative controls were e.g., smooth muscle cells in vessel walls and bronchioli. Occasional CK7+ endothelial cells were not scored as luminal positive cells. Statistical analysis The presence of tumor cells within the lumen of pulmonary arteries was evaluated using H&E and CK7. Continuous variables were described by mean and standard deviation, categorical variables by frequency and percentage. For relapse free survival (RFS) and overall survival (OS) analysis Kaplan-Meier curves were estimated and compared using the log-rank test. Statistical analysis was performed in SPSS version 26 (IBM Corp., Armonk, NY, USA). P-values <.05 were considered statistically significant. 10
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