Bladder Cancer Types

Globally, bladder cancer is the sixth most common cancer in men, and the 10th most common cancer overall¹.

Bladder cancer occurs when cells that make up the bladder begin to grow in an abnormal and uncontrolled way. Bladder cancers are assigned to different types according to the cell type they arise from, as determined by microscopic examination of urine samples and tissue biopsies. There are several types of bladder cancer, and each is associated with different risk factors and outlooks.

In this article we discuss the different types of bladder cancer and explain some of the terms that are often used to describe them.

What is the most common type of bladder cancer?

Urothelial carcinoma, also called transitional cell carcinoma, is the most common type of bladder cancer, accounting for approximately 9 out of every 10 cases.² This type of cancer starts in the urothelial cells lining the inner surface of the bladder wall. Cancerous urothelial cells form a tumour that can grow into the deeper layers of the bladder wall and spread to nearby lymph nodes and organs. In some instances, cancer cells may break away from the bladder tumour(s) and form new tumours in distant parts of the body. This is called metastatic bladder cancer.

Urothelial carcinoma bladder tumours may be classified as ‘non-muscle invasive’ or ‘muscle invasive’ and assigned to a specific ‘T’ category according to the nature and extent of their growth.

Non-muscle invasive urothelial carcinoma

Urothelial carcinoma is classified as non-muscle invasive if it has not spread beyond the urothelium or underlying connective tissue into the muscular layer of the bladder wall. Most patients (around 80%³) are diagnosed with this type of the disease.

Non-muscle invasive urothelial carcinoma tumours may be:

• Papillary or ‘Ta’ tumours. These finger-like tumours are based in the urothelium and grow outwards into the hollow centre of the bladder.
• Flat or ‘Tis’ tumours. These are flat tumours that can appear as a reddened, velvet-like area on the bladder lining. Also commonly referred to as ‘carcinoma in situ’, they have a greater tendency than papillary tumours to spread into the deeper layers of the bladder wall.
• T1’ tumours. This tumour type extends beyond the urothelium into the underlying connective tissue of the bladder wall.

Muscle invasive urothelial carcinoma

Muscle invasive urothelial carcinoma tumours have spread into or through the muscle layer of the bladder wall.

• ‘T2’ tumours have spread into the muscle layer of the bladder wall.
• ‘T3’ tumours have spread through the muscle layer and into the fatty tissue surrounding the bladder.
• ‘T4’ tumours have spread to nearby pelvic organs, the pelvic wall, or the abdominal wall.

As well as assigning a ‘T’ category, the commonly used ‘TNM’ clinical staging system also assigns urothelial carcinoma to an ‘N’ category (describes spread to nearby lymph nodes) and an ‘M’ category (describes spread to distant lymph nodes or organs). For further information regarding bladder cancer classification, see Bladder Cancer Stages.

Metastatic urothelial carcinoma

If urothelial carcinoma of the bladder spreads to distant organs or lymph nodes outside the pelvis it is called metastatic urothelial carcinoma. It is more common for muscle invasive tumours than non-muscle invasive tumours to spread in this way. Urothelial carcinoma can metastasise to almost any organ, but the most common sites are lymph nodes, bones, lung, and liver. 

What other types of bladder cancer are there?

Several less common types of bladder cancer make up the remaining approximately 10% of bladder cancers. Some examples of the uncommon types include:

• Squamous cell carcinoma: Squamous cells develop in the lining of the bladder as a result of irritation or inflammation. These cells may eventually become cancerous. Although squamous cell carcinoma is uncommon, making up around 4% of all bladder cancers,² it has a high likelihood of progression.
• Adenocarcinoma: This type of bladder cancer consists of glandular-type cells and is usually invasive. Overall, around 2% of bladder cancers are adenocarcinomas.²
• Small cell carcinoma: Small cell carcinomas of the bladder start in nerve-like cells. This bladder cancer type is rare, accounting for less than 1% of bladder cancers, but can grow rapidly and spread to other parts of the body.
• Sarcoma: A sarcoma is a type of cancer that begins in the body’s supporting tissues, such as bone, muscle, fibrous tissues, and fat. Very rarely, sarcomas may arise from the muscle or fat layers of the bladder.

Although the treatment for most bladder cancer types (other than sarcoma) is similar for early-stage tumours, different drugs may be used if chemotherapy is undertaken.

Other terms often used to describe bladder cancer

Although bladder cancer types are assigned based on the cells that the cancer originates from, several other terms may be used to describe the disease.

• Advanced bladder cancer is another term that may be used to describe metastatic bladder cancer. It means that the cancer has spread to distant parts of the body such as the lungs, bones, liver, or lymph nodes outside the pelvis.
• Locally advanced bladder cancer refers to cancer that has grown through the bladder wall, and possibly into nearby lymph nodes or organs, but has not spread to distant sites in the body.
• Bladder cancer stage describes where the cancer is located within the bladder and any sites of spread. As described above, the ‘TNM’ staging system assigns a patient’s bladder cancer to a tumour (T), lymph node (N) and metastasis (M) category. These categories may also be combined to give an overall stage number: an overall stage of 0 or 1 describes early disease, while stage 4 is the most advanced. For further information regarding staging, see Bladder Cancer Stages.
• Bladder cancer grade is based on the microscopic appearance of cancer cells and suggests how fast a cancer might grow. Low-grade cancer cells appear similar to normal cells and usually grow slowly, whereas high-grade cancer cells have a very abnormal appearance and tend to grow quickly. High-grade cancers are more likely than low-grade cancers to spread.

What is the most aggressive form of bladder cancer?

In general, bladder cancers that are muscle invasive and/or have high-grade cells are the most serious and aggressive. The less common types of bladder cancer such as squamous cell carcinoma, adenocarcinoma, and small cell carcinoma have a greater tendency to be muscle invasive compared to urothelial carcinoma. However, if left untreated, initially low-grade, non-muscle invasive urothelial carcinoma can progress into the bladder wall and spread to other parts of the body.

The prognosis for bladder cancer is very favourable when the disease is detected early, so it is important to see your doctor if you are experiencing symptoms that could be due to bladder cancer. The most common early sign of bladder cancer is the presence of blood in the urine (‘haematuria’). Other symptoms that may be experienced include urinary irritation (e.g., pain or a burning sensation during urination) and changes in bladder habits. For further information regarding the signs and symptoms of bladder cancer, see Bladder Cancer Symptoms.

How is bladder cancer detected? 

Several tests and procedures, including non-invasive genomic urine tests like Cxbladder, are available to determine whether an individual has bladder cancer or to establish an alternative diagnosis. Some of these clarify the presence of symptoms (such as haematuria) and others identify alternative causes of these symptoms (such as an infection). Importantly, these tests and procedures are used in combination to determine an overall diagnosis.
Learn more about bladder cancer detection     Learn more about Cxbladder 

 

Last Updated: 22 Oct 2024 06:45 am

• References
  1. World Cancer Research Fund International
  2. American Society of Clinical Oncology (ASCO). Bladder Cancer: Introduction. Accessed August 10, 2021.
  3. Afonso JP, Freitas R, António Morais FL, et al. Urothelial bladder cancer progression: lessons learned from the bench. J Cancer Metastasis Treat 2015;1:57-66.
  4. American Urological Association. Small Cell Carcinoma. Accessed August 16, 2021.

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