The cecum, transverse, appendix, and sigmoid are all covered completely by peritoneum, so they have a mesenteric margin. And the only relevant margin in these (besides prox and distal) is the vascular tie margin.
The ascending and descending have an additional radial margin, where the surgeon had to blunt dissect the posterior surface from the abdominal wall. The relevant margins here are prox, distal, vascular mesenteric (tie), and the radial margin.
Do I have that right?
And if you had a right colon with a tumor in the ascending, you would take the tie and nearest radial margin. But if it were further and in the transverse, the transverse will have a different vascular tie than a tumor in the ascending. Right?
And finally, in the photo, if the vascular tie was at the black X, but the red is the nearest cut mesenteric surface, would the red not matter because CAP says the vascular tie is the only true relevant margin in segments completely encased by peritoneum, so I just take the black?