Cancer Types – Kidney Cancer
Kidney Cancer: Overview
About the kidneys
Every person has 2 kidneys, which are located above the waist on both sides of the spine. These reddish-brown, bean-shaped organs are each about the size of a small fist. They are located closer to the back of the body than to the front.
The kidneys filter blood to remove impurities, excess minerals and salts, and extra water. Every day, the kidneys filter about 200 quarts of blood to generate 2 quarts of urine. The kidneys also produce hormones that help control blood pressure, red blood cell production, and other bodily functions.
Although most people have 2 kidneys, each works independently. This means the body can function with less than 1 complete kidney. With dialysis, a mechanized filtering process, it is possible to live without functioning kidneys. Dialysis can be done through the blood, called hemodialysis, or by using the patient’s abdominal cavity, called peritoneal dialysis.
About kidney cancer
Kidney cancer begins when healthy cells in 1 or both kidneys change and grow out of control, forming a mass called a renal cortical tumor. A tumor can be malignant, indolent, or benign. A malignant tumor is cancerous, meaning it can grow and spread to other parts of the body. An indolent tumor is also cancerous, but this type of tumor rarely spreads to other parts of the body. A benign tumor means the tumor can grow but will not spread.
Types of kidney cancer
There are several types of kidney cancer:
- Renal cell carcinoma. Renal cell carcinoma is the most common type of adult kidney cancer, making up about 85% of diagnoses. This type of cancer develops in the proximal renal tubules that make up the kidney’s filtration system. There are thousands of these tiny filtration units in each kidney. The treatment options for renal cell carcinoma are discussed later in this guide.
- Urothelial carcinoma. This is also called transitional cell carcinoma. It accounts for 10% to 15% of the kidney cancers diagnosed in adults. Urothelial carcinoma begins in the area of the kidney where urine collects before moving to the bladder, called the renal pelvis. This type of kidney cancer is treated like bladder cancer because both types of cancer start in the same cells.
- Sarcoma. Sarcoma of the kidney is rare. This type of cancer develops in the soft tissue of the kidney; the thin layer of connective tissue surrounding the kidney, called the capsule; or surrounding fat. Sarcoma of the kidney is usually treated with surgery. However, sarcoma commonly comes back in the kidney area or spreads to other parts of the body. More surgery or chemotherapy may be recommended after the first surgery.
- Wilms tumor. Wilms tumor is most common in children and is treated differently from kidney cancer in adults. This type of tumor is more likely to be successfully treated with radiation therapy and chemotherapy than the other types of kidney cancer when combined with surgery. This has resulted in a different approach to treatment.
- Lymphoma. Lymphoma can enlarge both kidneys and is associated with enlarged lymph nodes, called lymphadenopathy, in other parts of the body, including the neck, chest, and abdominal cavity. In rare cases, kidney lymphoma can appear as a lone tumor mass in the kidney and may include enlarged regional lymph nodes. If lymphoma is a possibility, your doctor may perform a biopsy (see Diagnosis) and recommend chemotherapy instead of surgery.
Types of kidney cancer cells
Knowing which type of cell makes up a kidney tumor helps doctors plan treatment. Pathologists have identified as many as 20 different types of kidney cancer cells. A pathologist is a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease. Computed tomography (CT) scans or magnetic resonance imaging (MRI) cannot always distinguish between benign, indolent, or malignant renal cortical tumors before surgery.
The most common types of kidney cancer cells are listed below.
- Clear cell. About 70% of kidney cancers are made up of clear cells. Clear cells range from slow growing (grade 1) to fast growing (grade 4). Immunotherapy and targeted therapy (see Treatment Options) are particularly effective at treating clear cell kidney cancer.
- Papillary. Papillary kidney cancer develops in 10% to 15% of patients. It is divided into 2 different subtypes, called type 1 and type 2. Papillary kidney cancer is currently treated in the same way as clear cell kidney cancer. However, many doctors recommend treatment through a clinical trial because treatment with targeted therapy is often not as successful for people with papillary kidney cancer as it is for people with clear cell kidney cancer.
- Sarcomatoid features. Each of the tumor subtypes of clear cell, chromophobe, and papillary in kidney cancer can show highly disorganized features under the microscope. These are often described by pathologists as “sarcomatoid.” This is not a distinct tumor subtype, but when these features are seen, clinicians are aware that this is a very aggressive form of kidney cancer.
- Medullary/collecting duct. This is a rare and highly aggressive cancer that is closely related to transitional cell carcinoma but is still considered a renal cortical tumor. It is more common in black people and is highly associated with having the sickle cell trait. Sickle cell trait means that a person has inherited the sickle cell gene from a parent. Collecting duct is more likely to occur in people between the ages of 20 and 30. Despite combinations of systemic chemotherapy and surgery, this form of kidney cancer has lower long-term survival rates.
- Chromophobe. Chromophobe is another uncommon cancer that is different from the other types. It may form indolent tumors.
- Oncocytoma. This is a slow-growing type of kidney cancer that rarely, if ever, spreads.
- Angiomyolipoma. Angiomyolipoma is a benign tumor that has a unique appearance on a CT (or CAT) scan (see Diagnosis) and when viewed under a microscope. Usually, it is less likely to grow and spread. It is generally best treated with surgery or, if it is small, active surveillance. An aggressive form of angiomyolipoma, called epithelioid, can in rare instances spread to nearby lymph nodes or organs such as the liver.
Read more about kidney cancer here.