<qa>  What is the aims of this study?The aims of this study is to compare the effectiveness of pecs block associated to a general anesthesia in terms of Piritramide consumption compared with a general anaesthesia alone and the chronic pain incidence in patients that undergoing either a lumpectomy or a mastectomy associated with axillary dissection This is a double-blind, placebo controlled study that will randomise breast cancer subjects in 1:1 ratio to receive a pecs block of Ropivacaine 3.5 mgml and Clonidine 5 μgml arm A versus placebo arm B. 