Fig. 1: Representative images of colon carcinomas from the COLOPEC trial in relation to the free peritoneal surface (H&E stains).

A, B (×20) are from cases with full peritoneal penetration where the tumor cells were growing onto the peritoneal surface within peritoneal clefts (in case B with inked surface). C (x20) demonstrates a case where the tumor cells reached directly to the free peritoneal surface (distance of 0 µm, arrow). D (×20), E (×20), and F (×4) show cases where the shortest distance of tumor cells to the free peritoneal surface was 60 µm, 167 µm, and 703 µm, respectively (black lines show the location of the measurements).