Furthermore, the heterogeneity among studies related to low Per2 expression and lymph node metastasis was obviously decreased in non-gastrointestinal cancer group (OR=3.89, 95%CI: 2.59∼5.84, Ρ<0.001, Ι2=1.4%, Ρ=0.363). Here, PER2 is linked to metastatic malignant neoplasm in the lymph nodes.