Analysis Of Clinical Characteristics Of Misdiagnosed Malignant Benign Renal Lesions

OBJECTIVE:To investigate the clinical features of the three most frequently misclassified benign renal lesions.MATERIALS AND METHODS:Patient records in our hospital with preoperatively misclassified renal angiomyolipoma (AML), renal oncocytoma (RO) and renal cyst were retrieved during a period from January 2008 to December 2014. Their demographic data, imaging features as well as treatment modalities were retrospectively analyzed to explore important factors involved in their misdiagnosis.RESULTS:Thirty-eight renal AML patients, thirty-five RO patients and thirty-one renal cyst patients were included in the present study. The percentage of those that received radical nephrectomy among renal AML, RO and renal cyst patients were 21.05%, 11.43% and 9.68% respectively. The misclassified renal AML patients received comparable radical nephrectomy with renal cell carcinoma patients but significantly more such surgeries compared with typical renal AML patients. No fat density on computed tomography (CT), hypoechoic on ultrasonography and small tumor size were the three important factors related to the misclassification of renal AML as malignancy. The clinical features of RO and kidney cancers have great overlaps, and central stellate scar sign on CT could not only present on RO but also on renal cell carcinoma. Though two thirds of our benign renal cysts series were suspected as malignancies for their high Bosniak classification, the other one third patients, however, had been misdiagnosed as solid tumors of kidney, and most of which were lesions with a diameter less than 2cm, hypoechoic on ultrasonography and slight to medium enhancement on CT.CONCLUSIONS:A significant number of benign renal lesions were misdiagnosed as malignancies, causing a large number of unnecessary surgeries, even radical nephrectomies. No fat density on CT, hypoechoic on ultrasonography and small tumor size are three main factors leading to the misclassification of renal AML. RO could hardly be differentiated from kidney cancer preoperatively by the regular available imaging modalities, and central stellate scar sign is not specific or diagnostic for RO. Benign renal cysts could be suspected as possible malignant tumors by presenting as complex renal cysts as well as solid masses; and pseudoenhancement of the small-sized and high-density renal cysts was the main reason for the renal cysts’misclassification as solid tumors.