<prompt> Least risk of CA breast is seen in -BRCA1BRCA2Li-Fraumeni syndromeAtaxia telangiectasia  <response>: Ans. is d i.e. Ataxia telangiectasia Only about 5 to 10 of breast cancers are caused by inheritance of germline mutations most important of which are BRCA-1 BRCA-2.Percent Incidence of Sporadic, Familial, and Hereditary Breast CancerSporadic breast cancer 65-75Familial breast cancer 20-30Hereditary breast cancer 5-10BRCA-145 BRCA-235 p53 Li-Fraumeni Syndrome1 STK 11LKB1 Peutz-Jeghners syndrome1 PTEN Cowden disease1 MSH2MLH1 Muir Torre syndrome1 ATM Ataxia-telangiectasia1 Unknown20 