A kidney tumor is an abnormal growth within the kidney. The terms “mass,” “lesion” and “tumor” are often used interchangeably. Tumors may be benign (non-cancerous) or malignant(cancerous). The most common kidney lesion is a fluid-filled area called a cyst. Simple cysts are benign. They do not progress to cancer and usually require no follow-up or treatment. Solid kidney tumors can be benign but are cancerous more than 80 percent of the time.
When a kidney tumor is suspected, a kidney imaging study is obtained. The initial imaging study is usually an ultrasound or CT scan. In some cases, a combination of imaging studies may be required to completely evaluate the tumor. If cancer is suspected, the patient should be evaluated to see if the cancer has spread beyond the kidney (metastasis). An evaluation for metastasis includes an abdominal CT scan or MRI, chest X-ray and blood tests. A bone scan is also recommended if the patient has bone pain, recent bone fractures, or certain abnormalities on their blood tests. Additional tests may be obtained when indicated.