Hyperechoic central tissue in kidney was seen by ultrasound radiologist. my urologist said nothing to worry and to ignore and no need for further testing. all blood tests & urine normal. other drs here said 30% possibility of malignancy. advise pls?

Trust your urologist more because he is liable, not doctors in this forum. If the finding is suspicious by US, urologist has to look at the images by himself and if he is unsure, he will discuss the case with the reading radiologist. In general, due to the liability and radiologist only reads the images without much knowledge about the case so he (she) has to suggest another test to make sure.