thanks for choosing health care magic..
well the white spot on your kindney may not necessarily be a cancer.
there are many coditions where there can be a white spot but your radiologist
is the best person to judge it, may be you will need a CT scan
to rule out any other pathology. ask for a proper report from the radiologist & discuss with your urologist the further plan of action, it may well be a stone or some local calcification . consult a urologist