Mucinous cystadenoma mimicking simple renal parenchymal cyst in a horseshoe kidney.

We report a case of mucinous cystadenoma in a horseshoe kidney which radiologically resembled a simple renal cyst. In the published literature, three cases of mucinous cystadenoma of renal origin have been reported. Although these tumors are believed to originate from the renal pelvis, the cyst in the present case originated from renal parenchyma. The significance of this particular case is the radiological features, which mimic a simple renal parenchymal cyst and contribute to the histopathological definition of an extremely rare disease.