The most common sites for recurrence of breast cancer are the lungs, liver, and bones. The frequency of peritoneal, gastrointestinal metastasis is significantly lower than those, and bilateral ureteral obstruction caused by peritoneal metastasis is relatively rare. A 66-year-old woman was referred to our hospital because of appetite loss and frequent urination. She was on adjuvant hormonal therapy for local recurrence of right breast cancer. She was diagnosed with bilateral ureteral obstruction due to extramural compression. Exploratory laparoscopy revealed omental cake and peritoneal nodules of which pathological examination showed peritoneal metastasis of invasive lobular carcinoma. Peritoneal metastases from breast cancer are unusual and consequently difficult to identify without non-invasive tools. Exploratory laparoscopy revealed that the cause of hydronephrosis in this case was peritoneal metastasis of invasive lobular carcinoma. Clinical history and histological study play a pivotal role in determining the correct diagnosis.
