Invasive lobular carcinoma accounts for 4 to 10% of breast cancers. The clinical and radiological diagnosis is difficult to make. Its progression is slower than that of ductal cancer, and the prognostic factors are more favourable. Its metastases are more frequently located in the digestive tract and the ovaries. It is more frequently bilateral. Its prognosis is not different from that of infiltrating ductal carcinomas. The choice of therapies depends on the individual characteristics of each patient and of the biological features of each tumour. However, lobular carcinomas seem to be less responsive to chemotherapy.