Myopericytoma of the ureter Incidental finding of a benign slowly growing tumor

We present a unique case of a 6 cm, incidental, ureteral myopericytoma which was initially believed to be an ovarian tumor with mass effect, causing hydroureteronephrosis. A 75-year-old woman presented with a three-month history of postprandial cramps and heartburn. A right distal ureterectomy with en-bloc resection of the mass was performed.Histologically, a well-circumscribed, cellular proliferation of uniform, cytologically bland, spindle cells was identified that had a multilayered, concentric growth pattern around numerous blood vessels. Immunohis-tochemically, the spindle lesional cells stained strongly and diffusely with antibodies against smooth muscle actin and failed to stain for pancytokeratin and S100 protein.