Idiopathic retroperitoneal fibrosis mimicking infiltrative malignancy: a case report.

The treatment strategy for an idiopathic retroperitoneal mass has not yet been established. Additionally, differentiating between benign and malignant is a challenge. Herein, we report a case in which we performed partial resection of a mass in a symptomatic patient with idiopathic retroperitoneal fibrosis that mimicked malignancy. A 44-year-old woman with an unremarkable medical history other than gallstones presented with a 1-month history of abdominal pain and repetitive vomiting. Imaging studies identified a large, retroperitoneal mass compressing the duodenum that had grown acutely over the preceding 2 weeks. The possibility that the mass was malignant could not be excluded. Considering the invasiveness and potential curability, we performed partial resection of the mass, which involved partial colonic resection with reconstruction, to allow for pathological diagnosis and intestinal obstruction treatment. The final pathological findings revealed that the mass consisted of hemorrhagic and fibrotic tissue without a tumorous component. The patient's postoperative course was unremarkable. She is alive 8 years postoperatively with no recurrence. In conclusion, a surgical approach, including biopsies, to idiopathic retroperitoneal fibrosis that mimics malignancy should be actively considered in symptomatic patients. Decisions regarding the required degree of surgical intervention call for sufficient, case-specific discussion.