Grading and staging of bladder cancer: How aggressive is my tumour?
Bladder cancers are not all the same. Some are small and confined to the bladder lining, whereas others are large, aggressive and invade into the bladder muscle. There are also tumours that are somewhere in between these two extremes.
The majority of bladder cancers do not invade the bladder muscle and so can be treated without removing the bladder (although this may be necessary in some cases). Many of these non-muscle invasive bladder cancers require repeated treatments as the cancer has a tendency to grow back inside the bladder but are not life-threatening. As a result, your urologist will want to keep a close eye on you and see you regularly for check-ups.
Hopefully, this webpage will make it easier for you to understand how urologists assess how aggressive a bladder cancer is based on the features of the cancer when looked at under a microscope and also based on additional findings from scans and telescopic examinations of your bladder.
Types of Bladder Cancer
There are several different types of bladder cancer and treatment will depend very much on the type, grade and stage of the cancer.
The type of bladder cancer is named after the type of cells in which they first occur, these are:
- Transitional cell carcinoma (TCC)
- Squamous cell carcinoma (SCC)
- Small cell carcinoma
TCC is the most common type of bladder cancer in the UK.
Grading of a Bladder Cancer
Grading of a bladder cancer is assessing how aggressive it is in terms of how abnormal its cells look like 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 of a bladder cancer is assessing how aggressive it is in terms of how deep it is invading 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 which is often performed with a CT scan.
This system of staging is also known as 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.
If the bladder cancer is confined to the bladder lining or urothelium it is staged Ta.
High grade cancer cells confined to the innermost layer of the bladder lining is staged CIS or carcinoma in situ. Unfortunately CIS is an aggressive form of bladder cancer despite it being confined to the innermost layer of the bladder.
If the bladder cancer grows into the connective tissue under the urothelium it is staged as T1.
The majority of bladder cancers fall into one of the above three categories and are termed non-muscle invasive bladder cancer.
If the bladder cancer grows into the bladder muscle it is staged T2.
If the bladder cancer grows through the bladder muscle to outside the bladder and into the fat around the bladder it is staged T3.
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 it is staged T4.
Sometimes a small letter p or c is written in front of the T, eg pTa or cT3.
- pT means the stage has been made based on pathological or microscopic findings.
- cT means the stage has been based on clinical (often based on imaging) findings.
If the bladder cancer has spread to lymph nodes then this is staged as N1, N2 or N3 depending on the number and position of the lymph nodes. If lymph nodes are not involved it is staged N0.
If the bladder cancer has spread to other places in the body it is staged M1. The vast majority of bladder cancers have not spread and are staged M0.
How aggressive is my bladder cancer?
Bladder cancers fall into five broad categories based on their grade and stage:
- Low risk non-muscle invasive bladder cancer
These are small (less than 3cm), single low grade (G1 or G2) pTa bladder cancers.
- Intermediate risk non-muscle invasive bladder cancer
These are large (greater than 3cm) or multiple low grade pTa bladder cancers. Small, single low grade pT1 tumours are also in this category. Also if low risk tumours keep growing back they fall into this category.
- High risk non-muscle invasive bladder cancer
These are high grade (G3) pTa or pT1 bladder cancers. All large (greater than 3 cm) or multiple T1 tumours are also included. CIS is also in this category.
- Muscle invasive bladder cancer
These are bladder cancers which are pT2 or pT3.
- Advanced bladder cancer
These are bladder cancers which are pT4 or have spread to lymph nodes (N1, N2 or N3) or other sites in the body (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 the bladder. Further details of treating bladder cancer can be found on this website.