The authors retrospectively reviewed 905 patients who underwent preoperative CT followed by surgical resection of the renal lesions at their institution between June 2009 and October 2013. Of these, final pathology was benign in 156 patients (17%). Overall, 140 patients with 163 benign tumors were included in this study and 3-sets of the CT interpretations by radiologists with varying levels of experience were analyzed.
The median size of 163 tumors was 2.9 cm (range 0.6 to 20.9). The final histological breakdown included: oncocytomas (54.6%, n=89), angiomyolipomas (AMLs) (30.7%, n=50), renal cysts (8.0%, n=13), and other miscellaneous benign tumors (6.7%, n=11). Preoperative CT were reported by primary radiologists as highly suspicious for renal cell carcinoma (RCC) (34.4%), ‘possible RCC’ (36.8%), equivocal whether RCC or benign tumor (8.0%), and 'suspicious for benign tumor’ (20.9%). More than half of tumors with highly suspicious for RCC were histologically diagnosed as oncocytomas (69.6%), followed by lipid poor (lp) AMLS (17.9%). The sensitivities of diagnosing oncocytomas were 3.4%, 9.0% and 13.5% in primary radiological reports, second blinded reviews, and third non-blinded reviews, respectively (p=0.055). Even non-blinded third reviews by an experienced radiologist found classic CT findings in only 13.5% of oncocytomas. The sensitivities of diagnosing AMLs were 46.0%, 58.0% and 62.0% in the 3-sets of CT interpretations, respectively (p=0.246). As for renal cysts, the sensitivities were 69.2%, 92.3% and 100% in the 3-sets of CT interpretations, respectively (p=0.051). In primary reports, it was found that the positive predictive values were 95.8% in lp-AMLs, 60.0% in oncocytomas, and 69.2% in renal cysts, respectively (p<0.05).
The authors therefore concluded, that current conventional CT imaging still has significant limitations in differentiating oncocytomas and lp-AMLs from renal cell carcinomas, even after images were re-examined by experienced radiologists. The authors suggest that in order to reduce unnecessary surgery, additional complementing imaging modalities may be needed, and percutaneous biopsy could be crucial in certain renal masses
Presented by: Shin To
Written By: Hanan Goldberg, MD, Urologic Oncology Fellow (SUO), University of Toronto, Princess Margaret Cancer Centre