A paraneoplastic retroperitoneal fibrosis resistant to corticosteroids treated with tamoxifen.

Retroperitoneal fibrosis (RPF) is a rare disease characterized by an inflammatory proliferative fibrosing process occurring in the retroperitoneum, often causing urinary tract obstruction. Medical therapy is not well-defined, but glucocorticoids have been the mainstay of therapy. Recently, positive response to tamoxifen, an antiestrogen drug, has been reported among patients with RPF. We report the case of a 65-year-old male with a renal cell carcinoma in the upper pole of the right kidney showing acute renal failure due to a biopsy-confirmed RPF determining bilateral hydronephrosis. After polar resection of the right kidney, a high-dose oral steroid therapy did not modify the hydronephrosis. At 6 months, therapy with tamoxifen determined the retroperitoneal fibrotic mass regression and resolved the ureteral obstruction, that persists at the 13th month of follow-up. Tamoxifen can be considered as an effective alternative to corticosteroids and immunosuppressors in treating RPF.