Tumor-like Accumulation of Uromodulin (Tamm-Horsfall Glycoprotein) in the Ureter. A Case Report of a Possible Diagnostic Pitfall.

Background: Uromodulin, also known as Tamm-Horsfall glycoprotein (THG), is the most abundantly produced protein appearing in normal urine. Under normal conditions it has several functions, the most important being the provision of a water-tight boundary to the end path of filtration and the prevention of urinary tract infections. Under certain conditions THG is accumulated in urinary tract organs and the deposition is most often clinically silent.

Case: We report a case of 78-year-old man with clinically evident hydronephrosis and stenosis of the right ureter. Clinically, a neoplasm was suspected. Histological examination of ureter tissue revealed abundant deposits of THG in the ureter wall without any inflammatory reaction.

Conclusion: In cases with deposition of eosinophilic material in the urinary tract organs, accumulation of THG should be considered in the differential diagnosis. To our knowledge this is the first report of tumor-like accumulation of THG in the ureter.