CYSTIC RENAL MASSES - A REEVALUATION OF THE USEFULNESS OF THE BOSNIAKCLASSIFICATION-SYSTEM

Rationale and Objectives. We evaluated the utility of the Bosniak syst em for classifying cystic renal masses on computed tomography (CT) sca ns. Methods. The CT scans of 20 patients with 24 cystic renal masses t hat were subsequently surgically removed or biopsied were reviewed ret rospectively. Masses were categorized using the Bosniak system and wer e correlated with the pathology results. Results. The final pathology results of the cystic renal masses were as follows: Seven of seven cat egory I lesions were benign, one of five category II lesions was benig n, zero of four category III lesions were benign, and zero of six cate gory IV lesions were benign. Neither of two unclassifiable cystic lesi ons were benign. The average enhancement of lesions in categories II, III, and IV was 6.3, 2.3, and 27.6 Hounsfield units (H), respectively. The two uncategorizable lesions had a mean enhancement of 26.8 H. Con clusion. The results of our study serve to underscore some limitations of the Bosniak classification system because most of our category II and all of our category III lesions were malignant, suggesting that mi nimally complex cystic renal masses may contain malignant cells. Contr ast enhancement of less than 10 H was demonstrated in lesions in categ ories II and III.