Aperio digital scanner at2 console

Patients were identified using surgical registries and pathology reports. All relevant clinical data was retrospectively collected from electronic patient record systems or paper records (patients operated before 2007 in Central Finland Central Hospital) used in the study hospitals. Tumour classification was updated according to the American Joint Committee on Cancer (AJCC) 8th edition of tumour-node-metastasis (TNM) classification [24 ]. Survival data until 31.12.2021 was received from Statistics Finland. The follow-up data was 100% complete.
Prospectively collected diagnostic haematoxylin- and eosin-stained (HE) histological samples of the primary CRC tumours and the pulmonary metastases were collected from the pathology archives and viewed with a light microscope by a histopathologist. The most representative slide (with the deepest invasion depth for the primary tumours) was selected and digitalized using an Aperio digital scanner AT2 Console (Leica Biosystems Imaging Inc. Nussloch, Germany).

Patients were identified from the archives using surgical registries and pathology reports. All relevant clinical data were retrospectively collected from electronic patient record systems used in the study hospitals. Tumour classification was updated to the American Joint Committee on Cancer (AJCC) 8^th edition of tumour-node-metastasis (TNM) classification [20 ]. Survival data until December 31, 2021, was received from Statistics Finland. The follow-up data were 100% complete.
Prospectively collected diagnostic H&E-stained histopathological slides of the primary tumours and pulmonary metastases were retrieved from pathology archives and reviewed by a pathologist. In pulmonary metastases, the most representative slide was selected for further analysis. In primary tumours, the slide with the deepest invasion depth was selected. The slides were digitalized with a × 20 objective magnification and resolution of 50,000 pixels per inch using an Aperio digital scanner AT2 Console (Leica Biosystems Imaging Inc., Wetzlar, Germany) or NanoZoomer-XR (Hamamatsu Photonics, Hamamatsu City, Japan).