Cancer as a Complex Phenotype: Pattern of Cancer Distribution within and beyond the Nuclear Family

Background The contribution of low-penetrant susceptibility variants to cancer is not clear. With the aim of searching for genetic factors that contribute to cancer at one or more sites in the body, we have analyzed familial aggregation of cancer in extended families based on all cancer cases diagnosed in Iceland over almost half a century. Methods and Findings We have estimated risk ratios (RRs) of cancer for first- and up to fifth-degree...