What is bladder cancer ?

Bladder cancer most often begins in the cells that line the inside of the bladder (urothelial cells).

TO REMIND YOU

The urinary excretory system includes, from top to bottom :

  • The two ureters, which emerge from the kidneys and function to carry urine to the bladder.
  • The bladder, a hollow organ located in the lower pelvis.
  • The urethra, which ensures the evacuation of urine.

The wall of the bladder is made up of different layers of tissue.

From the inside of the bladder to the outside, these layers are :

  • The mucosa , also called the urothelium, a tissue that lines the entire interior of the bladder and is in contact with urine. It is the inner lining of the entire urinary tract.
  • The submucosa , also known as the chorion, which contains blood vessels, nerves, and glands.
  • A muscle layer , called the muscularis, allows the bladder to stretch or contract.
  • Other tissues separate the bladder from certain organs :
    • A thin membrane, called the serosa , which covers the top of the bladder.
    • A loose tissue, called the adventitia , which covers the regions of the bladder where there is no serosa.
    • A layer of fat, called perivesical fat , which surrounds the bladder.

The bladder gradually fills with urine produced by the kidneys. When empty, it measures 6 cm in length and 5 cm in width. When full, it doubles in size. It stores urine until a sufficient amount (250 to 300 ml) fills the bladder and sends a signal to the brain to trigger the urge to urinate.

It is estimated that it takes about 10 to 15 years for normal cells to transform into bladder tumor cells1. There are two types of bladder tumors: non-muscle-invasive bladder tumors (NMIBT) and muscle-invasive bladder tumors (MIBT).

NMIBT are superficial tumors that account for about 80% of cases. A non-invasive tumor can be single or multiple. These tumors generally have a good prognosis. About 15% of them progress to invasive forms. MIBT are tumors that invade the muscle tissue. They can form metastases, primarily in the lymph nodes, bones, lungs, or liver.

💡 DID YOU KNOW ?

The formation of metastases is the real challenge posed by cancer.

Without metastasis, treating the primary tumor with localized treatments, such as surgery or radiotherapy, would be enough to cure most cancers. The presence of metastases results from the spread of cancer cells away from the primary tumor, requiring the use of treatments that also circulate throughout the body (systemic treatments), such as chemotherapy, targeted therapies, hormone therapies, or immunotherapies.

This spread of cancer cells to form metastases is a complex process. Cancer cells must leave the primary tumor, travel through lymphatic vessels and/or blood vessels to circulate in the body, then exit these vessels and invade a new organ where they multiply and form metastases.

In France, in 2023, 14,062 new cases of bladder cancer were diagnosed.

In terms of incidence (the number of new cases per year), bladder cancer ranks fifth among cancers in men and fifteenth among cancers in women. However, the number of cases is increasing among women, likely due to the rise in smoking among them.

1 - Dyrskjøt, L. et al. Bladder cancer. Nat Rev Dis Primers 9, 58 (2023).

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Article updated on Jan 20, 2025

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