Just because you had a gastroscopy six months ago and got an OK sign, it doesn't mean your risk of stomach cancer is zero. That’s because Borrmann type IV stomach cancer, a stomach cancer in which the stomach tissue becomes leathery and stiff and spreads to the sides, is more likely to be negative even when biopsied.

"In Korea, medical examinations are done once every two years after age 40, and most stomach cancers are detected at an early stage if they are done every two years. It is difficult for it to get bigger in a year," said Professor Park Do-joong of the Department of Gastrointestinal Surgery at Seoul National University Hospital. “In some cases, however, there were no problems last year, but a tumor suddenly progresses and metastasizes now."

Appearing on the YouTube channel “Seoul National University Hospital TV,” Professor Park explained the reason.

Advanced gastric cancer is classified into four types depending on its shape: “Bowman type 1” gastric cancer is a lump that suddenly appears on the gastric mucosa (bump); “Bowman type 2” gastric cancer is a depression in the gastric mucosa (ulcer): and “Bowman type 3” gastric cancer is a depression that spreads to the side (ulcer infiltration), so it is easy to detect.

However, “Bowman type 4” gastric cancer is known to be difficult to detect because it spreads downward and sideways (diffuse type) and is more likely to be negative even when biopsied.

"In the case of Bowman type 4 gastric cancer, which is stiffened like leather and spreads downward and sideways, it may not be detected even if an endoscopy was performed six months ago," Park explained.

A study published last year by researchers led by Professors Kim Tae-jun and Lee Jun-haeng of the Department of Gastroenterology and Professor Pyo Jeong-eui of the Health Sciences Center at Samsung Medical Center found that about 25 percent of patients diagnosed with advanced stomach cancer within six months to three years of a negative endoscopy had Bowman type 4 stomach cancer.

Bowman type 4 is a notoriously lethal form of stomach cancer. According to researchers at Samsung Medical Center, the cancer mortality rate associated with Bowman type 4 is 63 percent, compared to 26 percent for other stomach cancers than Bowman type 4.

For this reason, even if people have a final negative test for stomach cancer during a health checkup, it is important to follow up with their healthcare provider if medical staff ask them to repeat the test within three to six months.

"If cancer is suspected but not detected in the biopsy, it is necessary to repeat the test," Professor Park said.

Park added that patients with “intestinal epithelialization,” in which the structure of the stomach mucosa is destroyed due to a persistent inflammatory response in the stomach, can also detect stomach cancer early if they undergo an endoscopy once a year.