Some basic notions useful for understanding bladder cancer.
At the origin of bladder cancer, there is uncontrollable development of bladder cells.
When these cancer cells develop, they form a tumour that can spread to other parts of the body through remote metastases.
The bladder is a hollow organ of the small pelvis whose wall is very flexible and essentially composed of muscle.
Its main function is to store urine in the interval between urination.
Urine is produced by the kidneys and goes down into the bladder following channels called ureters.
During urination, the bladder muscle contracts, and urine is expelled from the bladder through a canal called the urethra.
Promotion and dissemination of bladder cancer
The bladder wall consists of several layers, each consisting of different cell types (see bladder cancer classification for a description of the different cell layers).
Most bladder cancers are born from the most inner layer of the bladder wall, the one that is in contact with urine.
This layer is called urothelium because its structure is that of a transitional epithelium.
As this cancer develops, it penetrates deep into the other layers of the bladder wall.
The more advanced the cancer, the more difficult it is to treat.
When this cancer has invaded the entire thickness of the bladder wall, it develops outside the bladder, invading adjacent structures and surrounding organs.
It also spreads into the lymph nodes, which are the primary pathways for cancerous spread, and to other organs located at a distance from the bladder, via metastases, especially to the bones, liver, and lungs.
Superficial or infiltrating bladder cancer
The severity of bladder cancers is often assessed based on the extent to which they extend into the depth of the bladder wall.
Surface cancers are limited to the most internal layers of the bladder wall: the transitional epithelium, and possibly after passing through the basal membrane the connective chorion under the mucous membrane.
They don’t reach the bladder muscle.
Intrusive cancers invade the bladder muscle and sometimes extend to perivenous fat. These cancers are more likely to spread and are also more difficult to treat.
Papillomatous carcinomas and planar carcinomas
Bladder cancers can occur as papillomatous carcinomas or planar carcinomas.
The difference is in the way the tumour develops.
Papillomatous carcinomas are visible to the eye of the operator during bladder endoscopy in the form of slender, digitiform tumours, such as algae or raspberries, from the bladder wall.
These papillomatous tumours develop towards the centre of the bladder, often without developing in the deeper layers of the bladder wall.
Flat Timor carcinomas do not develop towards the bladder cavity.
At the level of urothelium, normal urothelial cells are replaced by cancerous cells.
This tumour is also called in-situ plane carcinoma (ISC).
- American Cancer Society. Cancer Facts & Figures 2015. Atlanta, Ga: American Cancer Society; 2015.
- American Cancer Society. Cancer Facts & Figures 2016. Atlanta, Ga: American Cancer Society; 2016.
- American Cancer Society. Cancer Facts & Figures 2017. Atlanta, Ga: American Cancer Society; 2017.
- Kaufman DS, Shipley WU, Feldman AS. Bladder cancer. Lancet. 2009;374:239-249.