title: Idiopathic retroperitoneal fibrosis: clinicopathologic features and differential diagnosis.
abstract: Idiopathic retroperitoneal fibrosis (IRF) is a rare disease often causing obstructive uropathy. We evaluated the clinicopathologic features of 24 patients with IRF to characterize the histopathology of the disease and to provide a framework for the differential diagnosis with other retroperitoneal fibrosing conditions. Retroperitoneal specimens were analyzed by light and electron microscopy and by immunohistochemistry. Most patients presented with abdominal/lumbar pain, constitutional symptoms, and high acute-phase reactants. Overall, 20 had ureteral involvement and 13 developed acute renal failure. The retroperitoneal tissue consisted of a fibrous component and a chronic inflammatory infiltrate with the former characterized by myofibroblasts within a type-I collagen matrix. The infiltrate displayed perivascular and diffuse patterns containing lymphocytes, macrophages, plasma cells, and eosinophils. The perivascular aggregates had a central core of CD20(+) cells and a mantle of CD3(+) cells in equal proportions. In the areas of diffuse infiltrate, CD3(+) cells outnumbered the CD20(+) cells. Most plasma cells were positive for the IgG4 isotype. Small vessel vasculitis was found in the specimens of 11 patients. Our study indicates that a sclerotic background with myofibroblasts associated with a diffuse and perivascular infiltrate mainly consisting of T and B lymphocytes may be a pathological hallmark of IRF.
authors.affiliation: Department of Pathology and Laboratory Medicine, Pathology Section, University of Parma, Parma, Italy. domenico.corradi@unipr.it
authors.forename: D
authors.initials: D
authors.lastname: Corradi
authors.forename: R
authors.initials: R
authors.lastname: Maestri
authors.forename: A
authors.initials: A
authors.lastname: Palmisano
authors.forename: S
authors.initials: S
authors.lastname: Bosio
authors.forename: P
authors.initials: P
authors.lastname: Greco
authors.forename: L
authors.initials: L
authors.lastname: Manenti
authors.forename: S
authors.initials: S
authors.lastname: Ferretti
authors.forename: R
authors.initials: R
authors.lastname: Cobelli
authors.forename: G
authors.initials: G
authors.lastname: Moroni
authors.forename: A P
authors.initials: AP
authors.lastname: Dei Tos
authors.forename: C
authors.initials: C
authors.lastname: Buzio
authors.forename: A
authors.initials: A
authors.lastname: Vaglio
mesh_terms: D058186:Acute Kidney Injury / Q000000981:diagnostic imaging* / Q000209:etiology / Q000473:pathology*; D000328:Adult; D000368:Aged; D001402:B-Lymphocytes / Q000473:pathology; D003937:Diagnosis, Differential; D004804:Eosinophils / Q000473:pathology; D005260:Female; D005347:Fibroblasts / Q000473:pathology / Q000648:ultrastructure; D005355:Fibrosis; D006801:Humans; D007150:Immunohistochemistry; D008264:Macrophages / Q000473:pathology; D008297:Male; D008854:Microscopy, Electron; D008875:Middle Aged; D010950:Plasma Cells / Q000473:pathology; D012185:Retroperitoneal Fibrosis / Q000150:complications / Q000000981:diagnostic imaging* / Q000473:pathology*; D016176:T-Lymphocyte Subsets / Q000473:pathology; D014057:Tomography, X-Ray Computed; D014513:Ureter / Q000000981:diagnostic imaging / Q000276:immunology / Q000473:pathology; D014552:Urinary Tract Infections / Q000150:complications / Q000000981:diagnostic imaging / Q000473:pathology