Kidney cancer is the abnormal growth of cells in kidney tissue. In time, these cells form a mass called a tumor. Cancer begins when something triggers a change in the cells, and they divide out of control. A cancerous, or malignant, tumor can spread (metastasize) to other tissues and vital organs.
What are the types of kidney cancer?
The information in this document refers to renal cell carcinoma – the most common form of kidney cancer. However, there are different types of kidney cancer, including:
- Renal cell carcinoma (RCC): This is the most common form of kidney cancer in adults and accounts for 85% of all kidney cancers. Renal cell carcinoma usually develops as a single tumor in one kidney, but it can affect both kidneys. Renal cell carcinoma begins in the cells that line the small tubes that are part of the nephrons within the kidneys. (Renal is the Latin word for kidney, and the term “carcinoma” refers to cancer that begins in the cells that line or cover an organ.).
- Transitional cell carcinoma: Transitional cell carcinoma accounts for 6% to 7% of all kidney cancers. This cancer usually begins in the area where the ureter connects to the main part of the kidney. This area is called the renal pelvis. Transitional cell carcinoma also can occur in the ureters or bladder.
- Renal sarcoma: This is the least common form of kidney cancer, accounting for only 1% of kidney cancer cases. It begins in the connective tissues of the kidneys and, if not treated, can spread to nearby organs and bones.
- Wilms’ tumor: This is the most common type of kidney cancer in children. It accounts for about 5% of kidney cancers.
What causes kidney cancer?
The exact cause of kidney cancer is not known, but several risk factors have been identified. A risk factor is a characteristic or behavior that increases your chance of developing a disease. Risk factors for kidney cancer include:
- High blood pressure
- Family history
- Gene changes (mutations)
- Long-term dialysis treatment
- Tuberous sclerosis
- Von Hippel-Lindau (VHL) disease
If you have symptoms, your doctor will perform a complete medical history and physical exam. The doctor also may order certain tests that can help in diagnosing and assessing cancer. These tests can include:
- Urine tests: A sample of urine is tested to see if it contains blood. Even very small traces of blood, invisible to the naked eye, can be detected in tests of urine samples.
- Blood tests: These tests are done to count the number of each of the different kinds of blood cells, as well as look at different electrolytes in your body. A blood test can show if there are too few red blood cells (anemia), or if your kidney function is impaired (by looking at the creatinine).
- Computed tomography (CT or CAT) scan: This is a special X-ray that uses a computer to create a series of images, or slices, of the inside of the body. This test is often done with intravenous contrast (dye). Patients with impaired kidney function may not be able to receive the dye.
- Magnetic resonance imaging (MRI): This is a test that produces images of the inside of the body using a large magnet, radio waves and a computer.
- Ultrasound: This test uses high-frequency sound waves that are transmitted through body tissues to create images that are displayed on a monitor. This test is helpful in detecting tumors, which have a different density than healthy tissues.
Most cancers are grouped by stage, a description of the cancer that aids in planning treatment. The stage of a cancer is based on:
- The location and size of the tumor.
- The extent to which the lymph nodes are affected.
- The degree to which the cancer spread, if at all, to other tissue and organs.
How common is kidney cancer?
Kidney cancer represents about 3.7 percent of all cancers in the United States. Each year, more than 62,000 Americans are diagnosed with kidney cancer. The risk of kidney cancer increases with age. It is more common in men than in women.
Stages of kidney cancer
- Stage I: The tumor is 7 cm across or smaller and is only in the kidney. It has not spread to lymph nodes or other tissue. (Lymph nodes are small “filters” that trap germs and cancer cells, and store infection-fighting cells.).
- Stage II: The tumor is larger than 7 cm across but is still only in the kidney. It has not spread to lymph nodes or other tissue.
- Stage III: The tumor has spread to the major blood vessels – the renal vein and inferior vena cava – or into the tissue surrounding the kidney, or to nearby lymph nodes.
- Stage IV: The tumor has spread outside of the kidney to the adrenal gland (small gland that sits on top of the kidney), or to distant lymph nodes, or to other organs.
Tumors are also graded, which is a way of rating a tumor based on how abnormal its cells look. Tumor grading can also tell the doctor how fast the tumor is likely to grow. Tumors whose cells do not look like normal cells and divide rapidly are called high-grade tumors. High-grade tumors tend to grow and spread more quickly than low-grade tumors.
Treatment depends on the type of cancer, the stage and grade of the tumor, and the patient’s age and overall health.
Surgery is the most common treatment for kidney cancer. Several surgical options may be considered, including:
- Partial nephrectomy: The surgeon removes just the part of the kidney that contains the tumor.
- Radical nephrectomy: The surgeon removes the whole kidney, and some of the tissue around the kidney. Some lymph nodes in the area also may be removed.
When one kidney is removed, the remaining kidney usually is able to perform the work of both kidneys.
Surgery is the treatment of choice for most stages of kidney cancer. For chemotherapy for kidney cancer, there are many relatively new agents that block the blood flow to the tumor and put it into remission. These medications are typically taken by mouth and are generally well tolerated. The other approach is to use medication that activates the body’s own immune system to fight the tumor.
Some people with kidney cancer participate in clinical trials. Clinical trials are research programs conducted with patients to evaluate new medical treatments, drugs or devices. Clinical trials also are being conducted on new chemotherapy drugs and on new ways to use biological therapy for patients with kidney cancer.