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What is Bladder Cancer?

Bladder cancer occurs when cells in the bladder start to grow without control. Most tumours initially develop on the inner layer of the bladder, called urothelial cells. Certain tumors have the potential to penetrate deeper layers of the bladder. As the cancer progresses through these layers and into the muscle wall, treatment becomes challenging.

Additionally, urothelial cells present in the kidneys and ureters, the tubes linking the kidneys to the bladder, may also be affected. While bladder cancer typically occurs in the bladder, a similar type of cancer can also develop in the kidneys and ureters, though it is less common.

Types of Bladder Cancer

The most common bladder cancer is called “urothelial carcinoma” which begins in the urothelial cells that line the urethra, bladder, ureters, renal pelvis, and some other organs. A thorough examination of the entire urinary tract is conducted to detect any tumors.

Almost all bladder cancers are urothelial carcinomas, also called transitional cell carcinomas. While urothelial carcinoma accounts for the majority of bladder cancer cases, some individuals may receive a diagnosis of other less common types of bladder cancer.

The two most common types of bladder cancer are Non-Muscle Invasive Bladder Cancer (NMIBC) and Muscle Invasive Bladder Cancer (MIBC). Should cancer cells spread outside of the bladder walls, it is referred to as Advanced or Metastatic Bladder Cancer.

Non-Muscle Invasive Bladder Cancer

Approximately 75% of bladder cancers are non-muscle invasive. This means the cancer cells are only in the inner lining of the bladder and have not grown through the inner lining into the deeper muscle layer of the bladder. Doctors used to call this superficial bladder cancer.

Muscle Invasive Bladder Cancer

Approximately 25% of bladder cancers are muscle invasive. This means that cancer tumours have grown through the lining of the bladder into or through the bladder muscle. In most cases, this type of cancer is treated through surgery to remove the bladder (called a “radical cystectomy”) and to create a new path for urine to leave the body.

Advanced or Metastatic Bladder Cancer

Advanced bladder cancer occurs when the abnormal cells of a muscle invasive tumor spread beyond the bladder lining and may spread to the urethra or ureters or to nearby organs or tissues such as the prostate in men or the uterus, cervix, or vagina in women.

When bladder cancer metastasizes, it commonly goes to the lymph nodes in the pelvis or abdomen, the liver, and lungs. It may even metastasize to the bones or other parts of the body.

Upper Tract Urothelial Carcinoma

While most urothelial cancers (approximately 90-95%) arise in the bladder, upper tract urothelial cancer (UTUC) arises in the lining of the kidney (called the renal pelvis) or the ureter (the long, thin tube that connects that kidney to the bladder).

Rare Types of Bladder Cancer

Squamous cell carcinoma

Squamous cell carcinoma is cancer that begins in squamous cells, thin, flat cells lining the inside of the bladder. Of all the bladder cancer cases, squamous cell carcinoma represents only 1% – 2% of the cases. These cells are similar to skin cells found on the surface of your skin if you look at the cells under a microscope.

Adenocarcinoma

Adenocarcinoma is cancer that begins in glandular cells that are found in the lining of the bladder. Glandular cells in the bladder make mucus and other substances. Like squamous cell carcinoma, adenocarcinoma bladder cancer makes up roughly 1% of all bladder cancer cases. The cancer cells of adenocarcinoma are similar to the gland-forming cells found in colon cancers.

Small cell carcinoma

Small cell bladder cancer is a rare type of bladder cancer. It forms in neuroendocrine cells, which are nerve-like cells that release hormones in response to signaling from your nervous system. Compared with other types of bladder cancers, small cell bladder cancer is very aggressive. That means that it typically grows and spreads more quickly. Chemotherapy is a common treatment for this type of bladder cancer.

Sarcoma

Very rarely, some people get a cancer that starts in the bladder muscle or other structural tissues. These are different to cancers that start in the bladder lining. Cancers that start in the bladder muscle are called sarcomas. Treatment may include surgery, to remove the cancer cells and chemotherapy.

How Does the Urinary System Work?

The urinary system functions to rid our bodies of waste by filtering blood and disposing of these waste products via urine. The urinary system includes the kidneys, renal pelvis, bladder, ureters and urethra. Each of these organs work together to create and dispose of urine.

The majority of the urinary tract is lined with specialized transitional cells. As the core components of the human filtration system, the two kidneys are close to the backbone and protected by the rib. The kidneys work independently and play a crucial role in filtering roughly 20% of the total blood volume per minute and removing by-products from digestion and other bodily functions.

Once urine is produced, it is stored in the central region of the kidney known as the renal pelvis. The renal pelvis contracts at regular intervals, propelling the urine through the ureters. These slender, thin-walled tubes extend from the inside the renal pelvis to the bladder. The urine is then stored in the bladder until disposed of by way of the urethra.

What Does Your Bladder Do?

The bladder is a vital component of the urinary system.

The bladder, characterized by its thick walls, comprises a relatively thin inner layer encased by a thick muscle covering. This inner layer, or epithelium, consists of multiple layers of cells, also called the transitional cell layer. The bladder stores urine and for most individuals, the bladder can hold up to 1 pint or 16 ounces of urine at a time. Its capacity adjusts expanding or contracting based on fluid volume. When it contracts, it triggers a sequence of neurological signals to the brain and spinal cord and urine is expelled through the urethra outside the body.

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