Lesions can form within kidneys as a result of diseases such as Wilm's tumor, renal cell carcinoma, polycystic kidney disease, tuberous sclerosis and medullary cystic kidney disease, according to WebMD and Healthline. Simple kidney cysts are also common in people over 50, but they are not usually harmful.
Kidney tumors may or may not be cancerous, and small tumors on the kidneys may never grow. Therefore, doctors may not treat small tumors, but they actively observe them using regular imaging tests, according to WebMD.
Individuals with kidney cancer may have to take medication and possibly undergo surgery, chemotherapy or radiation. Kidney disease can be inherited or result from medical conditions such as diabetes and high blood pressure. According to Healthline, kidney disease that results from diabetes is the leading cause of kidney failure in the United States.