Cancer is a disease in which cells grow in an abnormal way. Normally, cells divide in a controlled manner to replace old or damaged cells. If cells keep dividing when new cells are not needed, a mass of tissue called a tumor forms.
A tumor can be benign or malignant. A benign tumor is not cancer and will not spread to other parts of the body. A malignant tumor is cancer. Cancer cells invade and damage tissue around them. They can also enter the lymph and blood streams, spreading to other parts of the body. Kidney cancer is the development of malignant cells in the kidneys.
Normal Anatomy and the Development of Kidney Cancer
The kidneys are 2 bean-shaped organs located in the rear of the abdominal cavity on each side of the backbone. The kidneys are part of the urinary system that filter excess water, salts, nutrients, and wastes from the blood. The kidneys also balance acids, and regulate fluid volume and blood pressure. Blood passes through special tubes inside the kidneys that can clear wastes, excess salt, nutrients, and water from the blood to create urine. The urine is then passed into long, muscular tubes called ureters that drain urine to the bladder.
An adrenal gland sits near the top of each kidney. The adrenal glands produce and secrete hormones, such as adrenaline and the steroid aldosterone. These hormones regulate the fight or flight response, and balance minerals, salts, blood volume, and metabolism. The location or severity of kidney tumors can influence the function of the adrenal glands.
Cell division and cell death are a normal process in the body to replace old or damaged cells. The cells inside of the kidneys may have a high rate of damage and cell turnover because they interact with waste products and toxins that are the blood. The turnover and irritation of the kidney cells can be increased with kidney diseases, dialysis, or chronic exposure to toxins. Excess turnover may increase the chance of cancer developing.
Kidney cancer can cause bleeding or interfere with kidney function. If it grows beyond the kidneys, the cancer can penetrate nearby structures, such as the ureters or bladder, and interfere with their function as well. Cancer can also spread to lymph nodes or blood vessels, which can carry cancer cells to other areas of the body. The most common sites for kidney cancer to travel to are the bones, lungs, liver, and brain.
Anatomy of the Kidney
Copyright © Nucleus Medical Media, Inc.
Types of Kidney Cancer
The types of kidney cancer are based on the area where they first develop. These include:
- Renal cell adenocarcinoma —Most common type. Develops in the lining of the tubes in the kidneys. There are subtypes of renal cell adenocarcinoma based on the cancer cells appearance under a microscope:
- Clear cell (most common)
- Transitional or urothelial carcinomas —Transitional cells are special cells that line the ureter. The cancer can develop in a section of the kidneys closest to the ureters and bladder.
- Wilms tumor —Most common kidney cancer in children.
- Sarcoma —Rare and arise from the connective tissue or blood vessels of the kidneys.
Kidney cancer may result in multiple tumors in one or both kidneys.