Benign Tumors

• Benign kidney tumors include renal papillary adenoma, angiomyolipoma and oncocytoma. Renal papillary adenomas are small and are usually found during an autopsy. Angiomyolipomas may spontaneously bleed and oncocytomas can be large and often need to be removed.
  
  

Malignant Tumors

• Renal cell carcinoma accounts for 85 percent of all kidney tumors, says "Robbins and Cotran Pathologic Basis of Disease." Wilms tumor is a malignant kidney tumor that occurs in children, and urothelial cell carcinoma is the third most common malignant kidney tumor.
  
  

Symptoms

• According to "Robbins and Cotran Pathologic Basis of Disease," symptoms of kidney tumors include flank pain, a palpable mass and blood in the urine. Other symptoms such as fever, weakness and weight loss are also associated with kidney tumors; however, most are often clinically silent.
  
  

Risk Factors

• According to "Robbins and Cotran Pathological Basis of Disease," cigarette smoking doubles an individual's risk of developing renal cell carcinoma. Additional risk factors include obesity, high blood pressure, unopposed estrogen therapy, asbestos exposure, petroleum exposure and heavy metal exposure.
  
  

Genetics

• Rare forms of inherited kidney tumors account for 4 percent of kidney cancers. These include Von Hippel-Lindau syndrome, hereditary clear cell carcinoma and hereditary papillary carcinoma.