AFP and yolk sac tumor: The definition of AFPGC by Inoue et al. was “preoperative AFP level exceeding 40 ng/mL with a decrease after gastrectomy, or raised preoperative AFP level (10–39 ng/mL) and resected tumor showing histologically characteristic features or immunohistochemically positive AFP production [30].” Of note, “histologically characteristic features” in the definition were regarded as “three subtypes: hepatoid type; yolk sac tumor-like type; and fetal gastrointestinal type [10].” And they found that preoperative serum AFP levels showed no correlation with patient prognosis.