CLDN18 and metastatic malignant neoplasm in the lymph nodes: In 78.1% (n = 68), Claudin 18.2-negative lymph node metastasis had corresponding negative primary tumor and in 70.1% (n = 23) Claudin 18.2-positive lymph node metastasis corresponded with positive primary tumors (p < 0.0001) (see Table 2).