HP and gastric cancer: In Japan, the risk for GC and precancerous lesions of GC can be stratified into four groups as follows: group A [Hp(−)PG(−)], group B [Hp(+)PG(−)], group C [Hp(+)PG(+)], and group D [Hp(−)PG(+)], according to the Helicobacter pylori (H. pylori or Hp) and the serum pepsinogen (PG) levels, with PGI ≤70 ng/ml and PGR ≤3 classified as PG-positive.