In a prospective unbiased analysis of a cohort of 446 unaffected carriers of an MMR gene mutation (MLH1, MSH2, MSH6, and PMS2) and 1029 of their unaffected relatives, as part of a Colon Cancer Family Registry, MMR gene mutation was found to confer increased cancer risks in a number of tumour types recognised to be associated with Lynch Syndrome (colorectal, endometrial, ovarian, renal, gastric, and urinary bladder), breast cancer and pancreatic cancer [10]. Here, MLH1 is linked to breast cancer.