Grading And Staging

GRADING AND STAGING OF BLADDER CANCER

An important part of assessing bladder cancer is grading the cancer according to how aggressive the cancer cells appear under a microscope, and staging which is assessing the extent of the cancer within the bladder and, more rarely, elsewhere in the body.  A bladder cancer will be described by using letters and numbers - these are explained below.

CATEGORIES OF BLADDER CANCER

Bladder cancers fall into five broad categories based on their grade and stage - a full explanation of these terms can be found below:

  • Low risk non-muscle invasive bladder cancer
    These are small (less than 3cm), single low grade Grade 1 or Grade 2) bladder cancers that haven't grown beyond the inner layer of the bladder. They are usually described as papillary (or mushroom like) and are called pTa - where the p indicates that this has been found out by biopsy.
  • Intermediate risk non-muscle invasive bladder cancer
    These are larger (greater than 3cm) or multiple low grade pTa bladder cancers. Small, single low grade pT1 tumours are also in this category where T1 indicates that the cancer has grown a little further into the bladder wall. Also if low risk tumours keep growing back they fall into this category.
  • High risk non-muscle invasive bladder cancer
    These are Grade 3 pTa or pT1 bladder cancers. All larger (greater than 3 cm) or multiple T1 tumours are also included. Carcinoma in Situ (CIS - where the cancer is present as a patch on the inner lining of the bladder) is also in this category.
  • Muscle invasive bladder cancer
    These are bladder cancers which are pT2 or pT3 which indicates that the cancer has grown further into the bladder wall and is found in the inner muscle layer.
  • Advanced bladder cancer
    These are bladder cancers which are pT4 which indicates that it has grown through the bladder wall or have spread to nearby lymph nodes to varying degrees - referred to as N1, N2 or N3) or to other sites in the body referred to as M1.

 

The majority of bladder cancers fall into either the low or intermediate risk non-muscle invasive category. These cancers are rarely life-threatening but unfortunately commonly grow back requiring surveillance and repeat treatments. Treatments for patients in these two categories are aimed at keeping and protecting your bladder.

High risk non-muscle invasive cancer is more difficult to treat and can progress to something more serious if not treated successfully. The most common treatment currently is called Immunotherapy (where BCG vaccine is used to encourage your immune system to ‘fight' the cancer) or, if that is either not appropriate or doesn't work it may be necessary to remove your bladder to avoid it spreading further.

If you have been diagnosed with muscle-invasive or advanced bladder cancer, a stage T2, T3 or T4 cancer, the cancer will have grown into the outer muscle layer of the bladder or beyond.  You may have been diagnosed straight after your first operation to remove your cancer tumour - referred to as a TURBT or Transurethral Resection of a Bladder Tumour or surveillance of a non-muscle invasive cancer which shows it has spread.  In either case, your clinician will very likely carry out further cancer staging and more intensive treatment which usually includes having to remove your bladder.

GRADING OF A BLADDER CANCER

Grading of a bladder cancer is assessing how aggressive it is in terms of how abnormal its cells look under a microscope. Those that are very abnormal grow more quickly.  Grade can be divided into low (cells look relatively normal and are therefore less aggressive) or high (cells are abnormal or poorly differentiated and therefore more aggressive) or can be scored from 1 (less aggressive, slowly growing) to 3 (aggressive, faster growing). Often this number has a G as a prefix to show it represents the grade, e.g. G1, G2 or G3.

 

Grade 1 (low) is the least aggressive meaning that the tumour is less likely to spread

Grade 2 is moderately aggressive

Grade 3 (high) is the most aggressive and most likely to grow and spread

STAGING OF A BLADDER CANCER

Staging is the process used by a doctor to assess the extent of a cancer in the bladder or, rarely, elsewhere in your body - with bladder cancer they will be looking to see how aggressive it is, how deep it has invaded into the bladder wall and whether it has spread to lymph nodes or other sites in the body.  Lymph nodes are glands which are found all over the body and are involved in helping the body fight infection as well as carrying fluid around the body. An example of swollen lymph nodes is when the glands in your neck swell during a throat infection.  Staging is based upon findings when examining the bladder cancer under a microscope and also based on imaging often a CT scan.

This system of staging can also be called the TNM system, which stands for tumour (T), lymph nodes (N) and spread to other sites in the body, also known as metastasis (M).

The bladder wall has 3 main layers as shown in the basic diagram below. The bladder lining is the urothelium, under this is connective tissue and deeper is the bladder wall muscle.

dia3.jpg

Staging – what the terms mean

The majority of bladder cancers fall into one of the following categories.

 

Ta

Papillary bladder cancer - if the bladder cancer is confined to the bladder lining or urothelium.  Usually looks like small growths, a bit like mushrooms, which can be removed by surgery and may not come back.

CIS

Carcinoma in situ - High grade cancer cells confined to the innermost layer of the bladder lining, the tumour is flat and not growing out of the bladder wall.  CIS is an aggressive form of bladder cancer despite it being confined to the innermost layer of the bladder.  It is more likely to come back than other types of superficial bladder cancer. 

T1

If the bladder cancer has grown from the bladder lining into the next layer, lamina propria, the connective tissue under the urothelium.  High grade T1 tumours can grow quickly.  About 30-40% of T1 bladder cancers come back.

T2

If the bladder cancer grows into the bladder muscle - muscle-invasive bladder cancer.

T3

If the bladder cancer grows through the bladder muscle to outside the bladder and into the fat around the bladder.

T4

If the bladder cancer grows through the bladder muscle to outside the bladder and into surrounding tissues such as the pelvic wall, prostate, womb or vagina.

 

If a small letter p or c is written in front of the T, eg pTa or cT3, or it is written with an N or M instead of a T

 

pT

The stage has been based on pathological or microscopic findings.

cT

The stage has been based on clinical (often based on imaging) findings.

N1, N2, N3

If the bladder cancer has spread to lymph nodes, numbered depending on the number and position of the lymph nodes. If lymph nodes are not involved it is staged N0.

M1

If the bladder cancer has spread to other places in the body. The vast majority of bladder cancers have not spread and are staged M0.

 

Diagram of bladder cancer stages

Diagram of different layers of the bladder showing stages

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