IntroductionCurrently, variability in surgical practice is a problem to be solved. The aim of this study is to describe the variability in the surgical treatment of breast cancer and to analyze the factors associated with it. MethodsThe study population included 1057 women diagnosed with breast cancer and surgically treated. Our data were from the CaMISS retrospective cohort. ResultsThe mean age at diagnosis was 59.3±5 years. A total of 732 patients were diagnosed through screening mammograms and 325 patients as interval cancers. The mastectomy surgery was more frequent in the tumors detected between intervals (OR=2.5 [95%CI: 1.8–3.4]), although this effect disappeared when we adjusted for the rest of the variables.The most important factor associated with performing a mastectomy was TNM: tumors in stage III–IV had an OR of 7.4 [95%CI: 3.9–13.8], increasing in adjusted OR to 21.7 [95%CI: 11.4–41.8].Histologically, infiltrating lobular carcinoma maintains significance in adjusted OR (OR=2.5 [95%CI: 1.4–4.7]).According to the screening program, there were significant differences in surgical treatment. Program 3 presented an OR of non-conservative surgery of 4.0 [95%CI: 1.8–8.9]. This program coincided with the highest percentage of reconstruction (58.3%). ConclusionsThis study shows that, despite taking into account patient and tumor characteristics, there is great variability in the type of surgery depending on the place of diagnosis.