by Jason Wasserman MD PhD FRCPC
June 3, 2022
Papillary urothelial carcinoma is a type of cancer that starts in a part of the body called the urinary tract. The urinary tract includes the bladder, ureters, urethra, and kidneys. Most tumours are found in the bladder.
Papillary urothelial carcinoma starts from specialized urothelial cells that cover the inside surface of the urinary tract and create a barrier called the urothelium. Tumours that are only found in the urothelium are called non-invasive while tumours that have spread into surrounding tissues are called invasive.
The diagnosis of papillary urothelial carcinoma is usually made by looking at a urine sample under a microscope. The diagnosis can also be made after a small sample of tissue is removed from the urinary tract during a procedure called a biopsy. After the diagnosis of papillary urothelial carcinoma is made, the entire tumour is usually removed in a procedure called transurethral resection (TURBT). For larger tumours that involve the bladder or kidney, part or all of the organ may need to be removed in a procedure called a resection.
Pathologists divide papillary urothelial carcinoma into two grades – low and high based on how the tumour cells look when examined under the microscope. Low-grade tumours are made up of cells that look more like normal urothelial cells while high-grade tumours are made up of more abnormal-looking cells that tend to be larger, darker, and less organized than normal urothelial cells. The grade is important because high-grade tumours are more likely to re-grow after treatment and spread to other parts of the body.
All papillary urothelial carcinomas start in a thin layer of tissue called the urothelium that covers the inside surface of the urinary tract. Non-invasive means that after careful microscopic examination, the entire tumour is seen within the urothelium. Because the tumour is non-invasive, the tumour cells are unable to spread to other parts of the body.
An invasive papillary urothelial carcinoma is a tumour that has spread into the layers of tissue below the urothelium. These layers include the lamina propria, muscularis propria, and perivesical soft tissue. Unlike non-invasive tumours, invasive tumours are able to spread to other parts of the body.
The distance that the tumour cells have travelled is called the depth of invasion and it can only be determined after the tumour is examined under the microscope. The depth of invasion is very important because tumours that invade deeper into the surrounding tissue are more likely to spread to other parts of the body. The depth of invasion is also used to determine the pathologic tumour stage (pT).
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 specialized vessels called lymphatics. The term lymphovascular invasion is used to describe tumour cells that are found inside a blood or lymphatic vessel. Lymphovascular invasion is important because these cells are able to metastasize (spread) to other parts of the body such as lymph nodes or 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 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 pathologic nodal stage (pN). Finding tumour cells in a lymph node is associated with a 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 margin means that no tumour cells were seen at the cut edge of the tissue. A margin is called 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 a 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 are given a tumour stage from T1 to T4 based on the depth of invasion.
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 0 or 1 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.