Hyperechoic renal cell carcinomas: increase in detection at US.

Recent reports have indicated that hyperechoic renal cell carcinomas (RCCAs) are more frequent among small cancers and that small cancers are being detected more frequently. To determine whether these trends have resulted in a change in the frequency of detection of hyperechoic RCCA and, in particular, in the frequency of RCCA mimicking angiomyolipomas (AMLs), the sonographic features of 90 pathologically proved RCCAs in 82 patients were retrospectively reviewed and correlated with tumor size. Tumor echogenicity was compared with that of normal renal parenchyma and classified as hypoechoic, isoechoic, slightly hyperechoic, or markedly hyperechoic. Thirty-one tumors were 3 cm in diameter or less, and 59 were larger than 3 cm. Ten (32%) of the tumors 3 cm in diameter or less were markedly hyperechoic and mimicked AMLs, whereas only one (2%) of the tumors larger than 3 cm had this appearance (P < .001). Eleven of the 90 tumors (12%) were markedly hyperechoic. Twenty-four (77%) of the small tumors were either slightly or markedly hyperechoic, compared with 19 (32%) of the larger tumors (P < .001). Because of the increased detection of small RCCAs in recent years, the number of hyperechoic cancers and the number of cancers mimicking AMLs have increased.