Postoperative peritoneal inflammatory granuloma mimicking peritoneal metastasis in a patient with breast cancer: a case report

Peritoneal metastasis from breast cancer is a relatively rare life-threatening condition. The gold standard for diagnosing peritoneal metastasis is a direct peritoneal biopsy. In this report, we describe an interesting case of peritoneal inflammation mimicking peritoneal metastasis in a patient with breast cancer, as confirmed by laparoscopic peritoneal biopsy. A 45-year-old woman with a history of right breast cancer presented with a peritoneal wall mass seen on an abdominal computed tomography (CT) in routine follow-up. She underwent right skin-sparing mastectomy with sentinel lymph node biopsy with direct to implant reconstruction 6 years prior and underwent right salpingo-oophorectomy 2 years before. Positron emission tomography-computed tomography (PET-CT) and abdominopelvic CT showed multiple enhancing nodules in small bowel mesentery and right peritoneal wall with a small amount of ascites, which led to a strong suspicion of peritoneal metastasis. After a multidisciplinary conference, the possibility of peritoneal seeding became doubtful. Laparoscopic biopsy was performed, and peritoneal wall mass biopsy was subsequently performed. Pathologic results showed no evidence of peritoneal metastasis of breast cancer. The peritoneal biopsy specimen revealed postoperative fibrosis and inflammation with some meal content. Although rare in breast cancer, peritoneal metastasis can produce a devastating outcome if left undiagnosed. Despite the imaging findings strongly suggesting metastasis, biopsy confirmation for the suspected lesion was necessary. This not only verifies true metastasis but also determines the treatment options available for the patient and thus unnecessary treatment can be avoided.