[A case report of cholesteatoma of the ureter difficult to distinguish from malignant ureter tumor].

An 81-year-old woman consulted us with low abdominal pain. A computed tomography (CT) image showed left hydronephrosis and a mass without calcification at the lower portion of the left ureter. A retrograde urogram showed an irregular filling defect at the lower portion of the left ureter that suggested an obstruction by a malignant ureter tumor. Therefore, total nephroureterectomy was performed. The surgical specimen showed a mass with a membrane, which could be detached easily from the ureter wall. The ureter wall showed hyperkeratosis upon histological examination, and the mass was diagnosed as cholesteatoma.