Colorectal cancer in a nuclear family. Familial or hereditary?

Because of the high incidence of colorectal cancer, familial aggregations of this disease are common. Differentiation between etiologies contributing to familial clustering (which may have resulted either from common environmental exposure or from mere chance) and primary genetic factors may prove vexing to the physician. This report deals with the myriad problems encountered when attempting to make such etiologic distinctions in order to provide appropriate surveillance and management, based upon tumor spectrum and natural history, for patients at increased cancer risk.