Cancerous tumours of the bladder

A cancerous tumour of the bladder can grow into nearby tissue and destroy it. It can also spread (metastasize) to other parts of the body. Cancerous tumours are also called malignant tumours.

Bladder cancer is often divided into 3 groups based on how much it has grown into the bladder wall.

• Non-invasive bladder cancer is only in the inner lining of the bladder (urothelium).
• Non-muscle-invasive bladder cancer has only grown into the connective tissue layer (lamina propria).
• Muscle-invasive bladder cancer has grown into the muscles deep within the bladder wall (muscularis propria) and sometimes into the fat that surrounds the bladder.

Urothelial carcinoma (also called transitional cell carcinoma) is the most common type of bladder cancer and makes up more than 90% of all bladder cancers. It starts in the urothelial cells that line the inside of the bladder (the lining is called the urothelium).

Urothelial carcinoma can be found in more than one place in the urinary tract (multifocal). So if urothelial carcinoma of the bladder is diagnosed, doctors will check other parts of the urinary tract for cancer. This includes checking the renal pelvis, ureters and urethra.

Non-invasive urothelial carcinomas can be described as papillary or flat (sessile) based on how they grow.

Papillary urothelial carcinomas look like small fingers and often grow toward the centre of the bladder (called the lumen). Non-invasive papillary urothelial carcinoma can be low or high grade. Papillary urothelial neoplasm of low malignant potential (PUNLMP) is the term used to describe a tumour when there is only a small chance that it will become invasive bladder cancer.

Flat urothelial carcinomas are flat tumours found on the lining of the bladder. They are high grade and more likely to grow deeper into the layers of the bladder wall. Non-invasive flat urothelial carcinoma is more commonly called carcinoma in situ (CIS).

Invasive urothelial carcinoma has grown beyond the inner lining into the deeper layers of the bladder wall.

Sometimes invasive urothelial carcinoma has different types of cells mixed with usual urothelial cancer cells (called divergent differentiation). When this happens, the bladder cancer usually grows and spreads quickly (it is aggressive), and it is more likely diagnosed when it’s advanced. Squamous cells, gland cells and small cells are most commonly found mixed with urothelial cancer cells.

There are rare subtypes of urothelial carcinoma called variants. These subtypes usually grow and spread quickly and tend to have a poorer prognosis than the usual urothelial carcinoma. Variants of urothelial carcinoma are named based on how the cancer cells look under a microscope and include:

• nested
• microcystic
• micropapillary
• lymphoepithelioma-like
• plasmacytoid
• sarcomatoid
• giant cell
• poorly differentiated
• lipid-rich
• clear cell

The following cancerous tumours of the bladder are rare and make up less than 10% of all bladder cancers.

Squamous cell carcinoma of the bladder is when flat squamous cells develop in the lining of the bladder. It is often associated with long-term (chronic) irritation or inflammation of the bladder. This irritation may happen from tubes (catheters) constantly being placed in the bladder over a long period of time, urinary stones or chronic urinary tract infections (UTIs).

Squamous cell carcinoma is usually invasive and diagnosed at a later stage. It is usually treated with surgery and sometimes chemotherapy.

Adenocarcinoma of the bladder starts in the gland cells of the bladder. It makes up less than 2% of all bladder cancers. Adenocarcinoma can spread to the bladder from another site (called secondary adenocarcinoma of the bladder). So doctors need to know where the adenocarcinoma started to make a proper diagnosis.

There are many subtypes of adenocarcinoma of the bladder, including mucinous, signet-ring and clear cell.

Adenocarcinoma of the bladder is usually treated with surgery. A radical cystectomy is done to remove the whole bladder. Adenocarcinoma tends to come back so chemotherapy is also used to treat it.

The urachus (also called the urachal ligament) is a connection between the belly button (navel) and bladder formed during the development of a fetus. A fine ligament remains in adults, but it has no function. Tumours can develop along the urachus and can become cancerous. Urachal cancer usually develops where the urachus joins the top of the bladder.

Urachal cancer is usually treated with surgery to remove the bladder, urachus, nearby lymph nodes and other surrounding tissue. Chemotherapy may be given after surgery.

Small cell carcinoma (small cell neuroendocrine carcinoma) is a type of neuroendocrine tumour (NET) that starts in the cells of the neuroendocrine system. Neuroendocrine cells are found in almost every organ of the body. Small cell carcinoma is usually a high-grade bladder cancer that grows and spreads quickly. Some people with urothelial carcinoma may also have small cell carcinoma.

Treatment for small cell carcinoma of the bladder usually includes chemotherapy followed by surgery to remove the whole bladder. Radiation therapy may also be used.

Find out more about neuroendocrine tumours (NETs).

Cancer can start in the soft tissues of the bladder, such as the muscle, blood vessels or fat. It is called soft tissue sarcoma of the bladder or bladder sarcoma. Many people initially diagnosed with soft tissue sarcoma of the bladder actually have sarcomatoid urothelial carcinoma.

The main risk for soft tissue sarcoma of the bladder is having had radiation therapy for a different type of cancer 20 to 30 years earlier.

Leiomyosarcoma (in adults) and rhabdomyosarcoma (in children) are the most common soft tissue sarcomas of the bladder.

Find out more about soft tissue sarcoma and rhabdomyosarcoma.