ESR1 and gastric cancer: In gastric cancer, ERα expression is higher in the diffuse type than in the intestinal type (Kitaoka, 1983; Tokunaga et al, 1986; Matsui et al, 1992; Zhao et al, 2003), and oestradiol (E2) enhances gastric cancer cell proliferation in vitro (Matsui et al, 1992; Takano et al, 2002).