What is kidney cancer?
Kidney cancer begins in the kidneys. Each of the two kidneys are about the size of an adult fist, bean-shaped and weigh around 150 grams each. One kidney is located at each side of the backbone, just under the rib cage. They are protected from injury by a large padding of fat, the lower ribs, and several muscles.
The kidneys play a major role in maintaining general health and wellbeing. Their purpose is to continuously sort non-recyclable waste from recyclable waste in the body while also cleaning the blood. The kidneys make urine from excess fluid and unwanted chemicals or waste in the blood.
Kidney cancer is caused by the abnormal growth of cells in the kidneys. Renal cell carcinomas (RCCs) make up approximately 90% of kidney cancer cases. Other types of kidney cancers include:
- Transitional cell carcinoma, or kidney pelvis cancer which begins in the lining of the kidney pelvis
- Wilms tumor (nephroblastoma), the most common cancer in children 14 and under
- Renal sarcoma, which is rare, develops in the soft tissue of the kidney
According to the American Cancer Society, kidney is the ninth most common cancer in the United States, accounting for approximately 3.7% of new cancer cases in 2016. Among men, the kidneys and renal pelvis (combined) is one of the top 10 cancer sites, and the seventh most common cancer.
Causes of kidney cancer
There are several risk factors of kidney cancer, including gender, age, race, and lifestyle choices. Men are nearly twice as likely to develop RCC as women. Kidney cancer is typically found in people age 50-75, with the average age of diagnosis being 64. The risk of developing the disease is slightly higher for African Americans and American Indians/Alaska Natives than for Caucasians.
Other risk factors include:
- Smoking
- Obesity
- Exposure to certain substances in the workplace
- High blood pressure
- Certain genetic and hereditary conditions (such as von Hippel-Lindau disease, hereditary papillary renal cell carcinoma, and others)
- Family history of the disease
- Advanced kidney disease
Symptoms of kidney cancer
Early kidney cancers do not usually cause any signs or symptoms, but larger ones may. Some possible signs and symptoms of kidney cancer include:
- Stomach pain
- Lower back pain on one side
- Blood in the urine
- Loss of appetite
These symptoms, however, can be caused by other benign diseases.
Kidney cancer staging
Staging is the process of determining how extensive the cancer is. It is an important part of diagnosis because the stage determines the most appropriate course of treatment options. The stages of kidney cancer range from Stage I (the least severe stage) to Stage IV. When patients are confirmed to have kidney cancer, the doctor will discuss the staging.
Stage I The tumor is 7 cm or smaller and is only located in the kidney. It has not spread to the lymph nodes or distant organs.
Stage II The tumor is larger than 7 cm and is only located in the kidney. It has not spread to the lymph nodes or distant organs.
Stage III Either of these conditions:
- A tumor of any size is located only in the kidney. It has spread to the regional lymph nodes but not to other parts of the body.
- The tumor has grown into major veins or perinephric tissue and may or may not have spread to regional lymph nodes. It has not spread to other parts of the body.
Stage IV Either of these conditions:
- The tumor has spread to areas beyond Gerota's fascia—the layer of connective tissue compressing the kidneys and the adrenal glands—and extends into the adrenal gland—small glands located on top of each kidney that produce hormones—on the same side of the body as the tumor, possibly to lymph nodes, but not to other parts of the body.
- The tumor has spread to any other organ, such as the lungs, bones, or the brain.