Abstract Background Distant spread from breast cancer is commonly found in bones, lungs, liver and central nervous system. Metastatic involvement of peritoneum and retroperitoneum is unusual and unexpected. Case presentation We report the case of a 67 year-old-woman who presented with gastrointestinal symptoms which revealed to be the clinical manifestations of peritoneal and retroperitoneal metastatic spread of an invasive lobular breast cancer diagnosed 15 years before. Conclusion To the best of our knowledge, the case presented is the third one reported in literature showing a wide peritoneal and extraperitoneal diffusion of an invasive lobular breast cancer. The long and complex diagnostic work up which led us to the diagnosis is illustrated, with particular emphasis on the multidisciplinary approach, which is mandatory to obtain such a result in these cases. Awareness of such a condition by clinicians is mandatory in order to make an early diagnosis and start a prompt and correct therapeutic approach.