It is possible that reduced function of DNA repair and cell-cycle control genes 
increases the individual susceptibility to malignant melanoma. As CHEK2 is a 
cell-cycle master controller, we tested the hypothesis that heterozygosity for 
the frameshift alteration CHEK2*1100delC is associated with increased risk of 
malignant melanoma. First, we performed case-control studies of 1,152 Danish and 
752 German individuals with malignant melanoma compared with 9,142 Danish and 
3,718 German controls. Second, we performed a meta-analysis of CHEK2*1100delC 
and malignant melanoma, involving 2,619 cases and 17,481 controls. Third, we 
examined the risk of malignant melanoma associated with CHEK2*1100delC 
heterozygosity in an analysis stratified for sun exposure, as well as for 
subtype and location on the body. The odds ratios for malignant melanoma for 
CHEK2(*)1100del heterozygotes compared with those for noncarriers were 2.01 (95% 
confidence interval (CI), 1.03-3.91) in Danes, 1.42 (95% CI, 0.46-4.31) in 
Germans, and 1.79 (95% CI, 1.02-3.17) in Danes and Germans combined. In a 
meta-analysis, the odds ratio of malignant melanoma for CHEK2*1100delC 
heterozygotes compared with that for noncarriers was 1.81 (95% CI, 1.07-3.05). 
Stratifications did not alter these results. CHEK2*1100delC heterozygotes have a 
twofold risk of malignant melanoma compared with noncarriers.