Both for EGFR and KRAS the category pleural and pericardial effusions was associated with a difference in mutation frequency compared to primary tumors (EGFR OR = 2.80 (95 % CI 1.22-6.41), p = 0.015; KRAS OR = 0.35 (95 % CI 0.14–0.86), p = 0.022). This evidence concerns the gene KRAS and pericardial effusion.