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. Immunohistochemically, the spindle lesional cells stained strongly and diffusely with antibodies against smooth muscle actin and failed to stain for pancytokeratin and S100 protein.