OBJECTIVES: Prognosis factors used for the management of infiltrative lobular carcinoma (ILC) are not different from those for infiltrative cuctal carcinoma (IDC). The aim of our work was to evaluate indications for conservative treatment for patients with ILC and to compare the results to those of patients with IDC. MATERIAL AND METHODS. Between 1985 and 1999 we retrospectively compared cases of 217 ILC with cases of 2155 IDC treated in Centre Rene Gauducheau, Nantes. RESULTS: Clinical size of tumors was not different between ILC and IDC but pathological size>30 mm was more frequent for IDC. Good prognosis factors as pathological SBR classification I or II, positive hormone receptor, and the lack of axillary lymph node involvement, were more frequent for ILC. Clinical examination underestimated tumor size more frequently of ILC than IDC (p=0.02). Secondary mastectomy for involved margin was more frequent for ILC than IDC (p=0.001). For tumor with good prognosis factors, such as T<20mm, lack of lymph node involvement and SBR I or II with conservative treatment, 5 years local relapse were less frequent for ILC than IDC (p=0.025). CONCLUSION: Parameters to validate conservative or radical treatment are the same for ILC and IDC. Diagnosis of ILC should not influence decisions regarding surgical treatment