This article will help you read and understand your pathology report for papillary urothelial carcinoma.
by Jason Wasserman MD PhD FRCPC, updated December 31, 2020
The bladder is a hollow organ located in the pelvis. The purpose of the bladder is to store urine and then to release it out of the body through a tube called the urethra. Urine is made in the kidneys and travels to the bladder by two long tubes called ureters.
The inside of the bladder is lined by cells called urothelial cells. These cells form a barrier on the inner surface of the bladder called an epithelium. The tissue directly below the epithelium is called the lamina propria. The inside of the ureters and urethra are also lined by urothelial cells.
Papillary urothelial carcinoma is a type of cancer. Papillary urothelial carcinoma develops from the urothelial cells in the epithelium. The tumour usually starts in the bladder but it can also start in the ureters or urethra.
The diagnosis of papillary urothelial carcinoma is usually made by looking at a urine sample under the microscope or on a biopsy taken from the bladder. After the diagnosis of urothelial carcinoma is made, the entire tumour is removed in a procedure called a resection.
When examined under a microscope, papillary urothelial carcinoma looks like finger-like projections of tissue covered in cancer cells. Pathologists call these projections papilla.
Most papillary urothelial carcinomas are non-invasive which means the cancer cells are only seen in the epithelium. A tumour is called invasive if the cancer cells have spread beyond the epithelium into the lamina propria below.
Whether or not a tumour is invasive can only be determined after tissue from the tumour is examined by a pathologist under the microscope.
Pathologists use the word grade to describe how different the tumour cells look compared to the normal, healthy urothelial cells. The size, shape, and colour of the tumour cells is used to determine the grade.
Based on the way the tumour cells look when examined under the microscope, papillary urothelial carcinoma is divided into two grades:
Grade is important because high grade tumours are more likely to re-grow after treatment and spread to other parts of the body.
This is the size of the tumour measured in centimetres (cm). The tumour is usually measured in three dimensions but only the largest dimension is described in your report. For example, if the tumour measures 4.0 cm by 2.0 cm by 1.5 cm, your report will describe the tumour as being 4.0 cm.
These tumours are often removed in multiple pieces. For this reason your pathologist may not be able to determine the size of the tumour.
There is a thick bundle of muscle in the wall of the bladder called the muscularis propria. When the bladder is full of urine, the muscularis propria squeezes which forces all of the urine out of the bladder and into the urethra.
The muscularis propria is found in the middle of the wall of the bladder below the lamina propria. Cancer cells that travel past the lamina propria can enter the muscularis propria. The movement of cancer cells into the muscularis propria is called invasion.
When examining a tissue sample from your bladder under the microscope, your pathologist will look for muscularis propria. If there is no muscularis propria in the tissue sample, your pathologist will not be able to say if there is invasion of the muscularis propria.
Tumours that invade the muscularis propria are more likely to spread to other parts of the body. and are less likely to respond to medications injected into the bladder. Invasion of the muscularis propria by cancer cells also increases the tumour stage (see Pathologic stage below).
All papillary urothelial carcinomas start in the epithelium on the inner surface of the bladder. Most tumours are called non-invasive which means the tumour cells were only found in the epithelium.
If the tumour cells spread beyond the epithelium into the lamina propria, the diagnosis changes to invasive papillary urothelial carcinoma. The movement of tumour cells from the epithelium into the lamina propria is called invasion.
When examining an invasive papillary urothelial carcinoma, your pathologist will look to see how far the tumour cells have traveled from the epithelium into the wall of the bladder.
The amount of invasion plays a very important role in the staging of papillary urothelial carcinoma (see Pathologic stage below) and is the most important feature when determining the type of treatment that will be offered.
Blood moves around the body through long thin tubes called blood vessels. Another type of fluid called lymph which contains waste and immune cells moves around the body through lymphatic channels.
Tumour cells can use blood vessels and lymphatics to travel away from the tumour to other parts of the body. The movement of tumour cells from the tumour to another part of the body is called metastasis.
Before tumour cells can metastasize, they need to enter a blood vessel or lymphatic. This is called lymphovascular invasion.
Lymphovascular invasion increases the risk that tumour cells will be found in a lymph node or a distant part of the body such as the lungs.
Lymph nodes are small immune organs located throughout the body. Tumour cells can travel from the tumour to a lymph node through lymphatic channels located in and around the tumour (see Lymphovascular invasion above). The movement of tumour cells from the tumour to a lymph node is called a metastasis.
Your pathologist will carefully examine all lymph nodes for tumour cells. Lymph nodes that contain tumour cells are often called positive while those that do not contain any cancer cells are called negative. Most reports include the total number of lymph nodes examined and the number, if any, that contain tumour cells.
Lymph nodes on the same side as the tumour are called ipsilateral while those on the opposite side of the tumour are called contralateral.
The number of lymph nodes found to contain tumour cells is used to determine the nodal stage (see Pathologic stage below). Finding tumor cells in a lymph node is associated with worse prognosis and may require additional treatment.
A margin is the normal tissue that surrounds a tumour and is removed with the tumour at the time of surgery.
A negative margins means that no tumour cells were seen at the cut edge of the tissue. A margin is considered positive when there is no distance between the tumour and the cut edge of the tissue. A positive margin is associated with a higher risk that the tumour will grow back (recur) in the same location after treatment.
The pathologic stage for papillary urothelial carcinoma is based on the TNM staging system, an internationally recognized system originally created by the American Joint Committee on Cancer.
This system uses information about the primary tumour (T), lymph nodes (N), and distant metastatic disease (M) to determine the complete pathologic stage (pTNM). Your pathologist will examine the tissue submitted and give each part a number. In general, a higher number means more advanced disease and worse prognosis.
All non-invasive papillary urothelial carcinomas are given a special classification called Ta in order to indicate their non-invasive status. In contrast, all invasive papillary urothelial carcinomas is given a tumour stage from T1 to T4 based on the extent of tumour invasion (see Invasion above).
Papillary urothelial carcinoma is given a nodal stage between 0 and 3 based on the number of lymph nodes that contain cancer cells and the location of those lymph nodes.
Papillary urothelial carcinoma is given a metastatic stage of M0 or M1 based on the presence of tumour cells at a distant site in the body (for example the lungs). The metastatic stage can only be determined if tissue from a distant site is submitted for pathological examination. Because this tissue is rarely present, the metastatic stage cannot be determined and is listed as MX.