Evaluation of renal cystic mass on ultrasonogram and computed tomogram: usefulness of magnetic resonance imaging and renal angiography--category III by Bosniak: report of 5 cases
Bosniak classification of renal cystic massesis an extremely useful management tool. Of category I-IV by Bosniak, category III lesion is moderately complicated cyst, which cannot be confidently distinguished from malignancy radiologically. Here, we reviewed the clinical course of 5 patients with pathologically proven category III mass by Bosniak in order to evaluate the usefulness of magnetic resonance imaging (MRI) and renal angiography. Two of the 5 lesions were benign (hemorrhagic cyst) and the other were malignant (RCC). On MRI, the results of 5 lesions were true positive in 1 and false negative in 2. On angiography, the results were true positive in 2 and false negative in 1. MRI has an important role in detection of mass. Angiography is necessary for making a definitive diagnosis of the indeterminate renal cystic masses on US and CT as RCC, but cannot increase enough diagnostic confidence in small cystic renal masses. We experienced indeterminate 2 masses (case 1 and 4) on these four imaging techniques, which were RCC and hemorrhagic cyst, respectively. In category III lesions, if malignant finding was detected by MRI or angiography, we believe that surgical exploration should be performed. But, an absolute decision tree for management of the complicated renal cystic mass has not been published, and further investigation should be required.