What Is Bladder Cancer?
A plain-language overview of bladder cancer, where it starts, its main types, and how it is found and treated, based on National Cancer Institute resources.
Source: National Cancer Institute · NCI reviewed 2023-02-16 · Verified 2026-07-02
The 30-second version
Bladder cancer happens when cells in the bladder start to grow without control. The bladder is a hollow, balloon-shaped organ in the lower abdomen that stores urine. Almost all bladder cancers start in the cells that line the inside of the bladder. Using tobacco, especially smoking, is a major risk factor.
Key takeaways
- Bladder cancer occurs when cells in the bladder grow without control.
- The bladder is a hollow, balloon-shaped organ in the lower abdomen that stores urine made by the kidneys.
- Almost all bladder cancers are urothelial carcinoma, which begins in the cells that line the bladder.
- Using tobacco, especially smoking cigarettes, is a major risk factor for bladder cancer.
- Doctors also describe bladder cancer as non-muscle-invasive or muscle-invasive, depending on whether it has reached the muscle wall.
- Many bladder cancer symptoms are also seen with other, less serious conditions.
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The full explanation.
The simple version
Bladder cancer occurs when cells in the bladder start to grow without control. The bladder is a hollow, balloon-shaped organ in the lower part of the abdomen that stores urine.
The bladder has a muscular wall. This lets it get larger to store urine made by the kidneys, and shrink to squeeze urine out of the body.
In short: bladder cancer begins when cells in the bladder grow out of control.
How the bladder works
The bladder and kidneys work together to remove wastes from the body through urine:
- Tiny tubules in the kidneys filter and clean the blood.
- These tubules take out waste products and make urine.
- The urine passes from each kidney through a long tube called a ureter into the bladder.
- The bladder holds the urine until it passes through a tube called the urethra and leaves the body.
There are two kidneys, one on each side of the backbone, above the waist.
Types of bladder cancer
Bladder cancers are named after the type of cell where the cancer started.
- Urothelial carcinoma (also called transitional cell carcinoma) begins in the urothelial cells, which line the urethra, bladder, ureters, renal pelvis, and some other organs. Almost all bladder cancers are urothelial carcinomas. These cells are also called transitional cells because they can stretch when the bladder is full and shrink when it is empty.
Other types of bladder cancer are rare:
- Squamous cell carcinoma begins in thin, flat cells lining the inside of the bladder. It may form after long-term irritation or infection.
- Adenocarcinoma begins in glandular cells in the lining of the bladder. These cells make mucus and other substances.
- Small cell carcinoma of the bladder begins in nerve-like cells that release hormones into the blood.
In short: almost all bladder cancers are urothelial carcinoma, which starts in the cells that line the bladder.
In place or spread
There is another way to describe bladder cancer, based on whether it has reached the muscle wall:
- Non-muscle-invasive bladder cancer has not reached the muscle wall of the bladder. Most bladder cancers are non-muscle-invasive.
- Muscle-invasive bladder cancer has spread through the lining of the bladder and into the muscle wall of the bladder or beyond it.
Risk factors and finding it
Using tobacco, especially smoking cigarettes, is a major risk factor for bladder cancer. Your healthcare team can explain other risk factors and what you can do to lower your risk.
Many bladder cancer symptoms are also seen with other, less serious conditions. Doctors use several tests to diagnose and stage bladder cancer, and there are different ways it can be treated.
Everyone's situation is different. Your care team is the best source of information about your own health and any next steps.
Watch instead
Animated lessons are in production. Here’s the planned video slate for this topic — each one will be based on the same NCI-sourced explanation you’re reading.
What Is Bladder Cancer: the quick overview
A one-breath explanation you can watch before an appointment.
Coming soonWhat Is Bladder Cancer, explained simply
The core ideas with friendly animation and plain language.
Coming soonUnderstanding what is bladder cancer — full lesson
A deeper walkthrough covering the key takeaways and common questions.
Coming soonVideo transcript▾
A full, readable transcript will appear here when the video is published — so the lesson is accessible whether you prefer to watch, listen, or read. For now, the article above is the complete text version.
Suggested animation storyboard▾
- 1Open on a calm title card: "What Is Bladder Cancer?" with the Cancer Explained mark.
- 2Narrator reads the 30-second summary while a soft animated diagram builds on screen: "Bladder cancer happens when cells in the bladder start to grow without control. The bladder is a hollow, balloon-shaped organ in the lower abdomen that stores urine. Almost all bladder cancers start in the cells that line the inside of the bladder. Using tobacco, especially smoking, is a major risk factor."
- 3Scene 2: illustrate the idea — "Bladder cancer occurs when cells in the bladder grow without control."
- 4Scene 3: illustrate the idea — "The bladder is a hollow, balloon-shaped organ in the lower abdomen that stores urine made by the kidneys."
- 5Scene 4: illustrate the idea — "Almost all bladder cancers are urothelial carcinoma, which begins in the cells that line the bladder."
- 6Close on a reminder card: this is educational only; talk with your healthcare team, and a link to the NCI source.
Words to know
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Quick knowledge check
According to this article, what is the bladder?
Frequently asked questions
▸Where does bladder cancer start?
Bladder cancer starts in the bladder, a hollow, balloon-shaped organ in the lower part of the abdomen that stores urine. Almost all bladder cancers begin in the urothelial cells that line the inside of the bladder.
▸What is the most common type of bladder cancer?
Urothelial carcinoma, also called transitional cell carcinoma, is by far the most common type. It begins in the urothelial cells that line the urethra, bladder, ureters, and renal pelvis. Almost all bladder cancers are urothelial carcinomas.
▸What does non-muscle-invasive bladder cancer mean?
Non-muscle-invasive bladder cancer is cancer that has not reached the muscle wall of the bladder. Most bladder cancers are non-muscle-invasive. Muscle-invasive bladder cancer has spread through the lining and into the muscle wall or beyond it.
▸What is a major risk factor for bladder cancer?
Using tobacco, especially smoking cigarettes, is a major risk factor for bladder cancer. Your healthcare team can explain other risk factors and steps that may lower your risk.
▸How is the bladder connected to the kidneys?
The kidneys filter and clean the blood and make urine. The urine passes from each kidney through a tube called a ureter into the bladder, where it is stored until it leaves the body through a tube called the urethra.
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Questions to ask your healthcare team
Consider bringing these questions to your next appointment.
- What type of bladder cancer do I have, and where did it start?
- Is my bladder cancer non-muscle-invasive or muscle-invasive?
- What tests do I need to learn more about my bladder cancer?
- What are my treatment options, and what are the possible side effects?
- How will treatment affect my daily life?
- Where can I find reliable information and support?
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