How much of the stomach is removed in people who have stomach cancer?

Part or whole remova. The type of surgery- partial or total gastrectomy- depends on the location, extent and type of stomach cancer. The surgical plan will be discussed by your surgeon after reviewing your endoscopy, biopsy and ct scan results. Sometimes surgery is done for emergent reasons- uncontrollable bleeding, obstruction, etc.
Depends on location. How much of the stomach is removed depends on the size and location of the tumor. Sometimes only 1/3rd of the stomach needs to be removed, but sometimes the entire stomach must be removed. One issue is that stomach cancer tends to spread beyond the visible edges of the tumor, so wide margins (extra stomach) are necessary to make sure all the cancer is out.