Pseudocyst formation in retroperitoneal fibrosis relapse.

We describe a 45-year-old male patient with recurrent retroperitoneal fibrosis (RPF), in whom a pseudocyst in the peri-aortic fibrotic mantle was diagnosed. Without any intervention other than oral treatment with tamoxifen, the pseudocyst showed significant regression. Although rare, pseudocyst formation may sometimes appear in RPF and may mimic other benign and malignant conditions. This is the first paper to describe pseudocyst formation in an RPF relapse.