The Comparison between Pre- and Postoperative Diagnosis in Renal Masses Smaller than 3cm in Diameter

Kim, Sang Jin; Oh, Wook; Jeon, Seong Soo; Kim, Bo Hyun; Choi, Han Yong; Chai, Soo Eung

Abstract

PURPOSE: Small renal parenchymal masses smaller than 3cm in diameter have been discovered with increasing frequency. This increment also increased the detection of benign tumor as well as the renal cell carcinoma. However many of them are radiologically indeterminate. We compared the results of pathologic examinations and preoperative radiologic features to determine the characteristics in small renal masses that preoperatively differentiate benign tumors from the malignant tumors.
MATERIALS AND METHODS
27 patients who had operative management due to renal masses smaller than 3cm in diameter were retrospectively analysed. Mean age of the patients was 52.3 years and mean diameter of renal masses was 2.1+/-0.8cm. Preoperative ultrasonoraphy(USG) and computerized tomography(CT) findings were compared with postoperative results of pathologic examinations.
RESULTS
Of 27 patients, 17(63%) were renal cell carcinomas, 5(7.4%) were angiomyolipomas(AMLs), 3(11.1%) were complicated cysts, 1(3.7%) was oncocytoma, 1(3.7%) was leiomyoma. Of the typical enhancement patterns of renal cell carcinoma on CT, heterogenous enhancement(29.4 vs. 14.3%), central necrosis(47.1 vs. 14.3%) were more frequent in small RCCs than small benign solid renal masses. However, early enhancement and delayed wash-out pattern(64.7 vs. 85.7%) was less frequent in small RCCs than small benign solid renal masses. All small cystic masses were shown the radiologic findings of Bosniak classification III or IV. All AMLs appeared to be sonographically homogeneous hyperechoic masses that were highly suggestive of AML. However, none of RCCs showed these sonographic findings.
CONCLUSIONS
In small renal parenchymal mass smaller than 3cm in diameter, postopertive benign tumors were not uncommon regardless of the malignant features on the CT findings. Retrospectively , USG might be a better choice for AML detection than CT. Therefore, both USG and CT should be included in preoperative workup for small renal masses.