Cancerous tumours of the renal pelvis and ureter

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

Urothelial carcinoma (also called transitional cell carcinoma) is the most common cancer of the renal pelvis or ureter. It makes up about 90% of all upper urinary tract tumours. Urothelial carcinoma starts in the urothelial cells that line the inside of the renal pelvis and ureter (the lining is called the urothelium).

Urothelial carcinoma starts in the renal pelvis more often than the ureter. It may also be found in both the renal pelvis and ureter.

About 20% to 40% of people with urothelial carcinoma of the renal pelvis or ureter will develop bladder cancer as well. So if urothelial carcinoma of the renal pelvis or ureter is diagnosed, doctors will check other parts of the urinary tract for cancer. This includes checking the bladder and urethra.

Urothelial carcinoma may be described as non-invasive or invasive based on how much it has grown into the wall of the renal pelvis or ureter.

Non-invasive urothelial carcinoma is when the cancer is only in the inner lining of the renal pelvis or ureter. It can be described as papillary or flat (sessile) based on how they grow:

Papillary urothelial carcinomas look like small fingers and tend to grow toward the centre of the renal pelvis or ureter. Non-invasive papillary urothelial carcinoma can be low or high grade. Some low-grade tumours have a small chance of becoming invasive cancer. These tumours are called papillary urothelial neoplasms of low malignant potential (PUNLMP).

Flat urothelial carcinomas are tumours that grow along the lining of the renal pelvis or ureter. They are high grade and more likely to grow deeper into the layers of the renal pelvis or ureter wall. Non-invasive flat urothelial carcinoma is more commonly called carcinoma in situ (CIS).

Invasive urothelial carcinoma has grown into deeper layers within the wall of the renal pelvis or ureter. It may have grown through the wall to areas outside the renal pelvis or ureter.

Sometimes invasive urothelial carcinoma has different types of cells mixed with the usual urothelial cancer cells (called divergent differentiation). When this happens, cancer of the renal pelvis or ureter usually grows and spreads faster (it is aggressive). It is then more likely to be 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 renal pelvis or ureter are rare.

Squamous cell carcinoma of the renal pelvis or ureter is when flat squamous cells develop in the lining of the renal pelvis or ureter. It is often associated with long-term (chronic) irritation or inflammation of the renal pelvis and ureter. This irritation may happen from chronic urinary stones or chronic urinary tract infections (UTIs).

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

Adenocarcinoma starts in gland cells. This cancer can start in the renal pelvis or ureter, but more often it spreads to the renal pelvis or ureter from another site (called secondary adenocarcinoma). So doctors need to know where the adenocarcinoma started to make a proper diagnosis.

There are many subtypes of adenocarcinoma of the renal pelvis or ureter including mucinous, signet-ring and clear cell.

Adenocarcinoma of the renal pelvis or ureter is usually treated with surgery. It tends to come back, so chemotherapy is also used to treat it.