Bladder cancer TNM staging helps to determine the disease prognosis and to select an appropriate treatment strategy. It is the most commonly used system for staging bladder cancers by the medical community.
“T” stands for “Tumor Size”, “N” for “Lymph Nodes”, and “M” for “Metastasis”. Numbers and/or letters after T (a, is, 1, 2a, 2b, 3, 4a, and 4b), N (0, 1, 2, and 3), and M (0, 1a, and 1b) provide more details about each of these factors.
Higher the number means higher the severity of the disease. Once T, N, and M categories are determined through different diagnostic techniques, this information is combined to assign an overall stage (from 0 to IV) to the disease.
Ta – Non-invasive papillary carcinoma also known as the papillary urothelial neoplasm of low malignant potential (PUNLMP)
Tis – Carcinoma in situ (Flat tumor; Pre-cancerous or cancer cells present only in the superficial layer of bladder mucosa)
T1 – Tumor invades lamina propria (subepithelial connective tissue)
T2a – Tumor invades the inner muscular layer (superficial muscularis propria)
T2b – Tumor invades the outer muscular layer (deep muscularis propria)
T3 – Tumor invades the perivesical tissue (fatty tissue around bladder)
T4a – Tumor invades the surrounding structures like prostate, seminal vesicles, uterus, vagina
T4b – Tumor invades the pelvic wall or abdominal wall
N1 – Tumor has spread to one regional lymph node in true pelvis
N2 – Tumor has spread to multiple regional lymph node in true pelvis
N3 – Tumor has spread to common iliac lymph nodes
M1a – Tumor spread to lymph nodes beyond common iliacs (non-regional)
M1b – Tumor spread to one or more distant organs such as lungs, bones, liver, peritoneum, etc.
Bladder Cancer Staging
|0a||Ta N0 M0|
|0is||Tis N0 M0|
|I||T1 N0 M0|
|II|| T2a N0 M0 |
T2b N0 M0
|IIIa|| T3 N0 M0 |
T4a N0 M0
T1-4a N1 M0
|IIIb||T1-4a N2-3 M0|
|IVa|| T4b Any N M0 |
Any T Any N M1a
|IVb||Any T Any N M1b|
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Watch this video to better understand TNM staging for Bladder Cancer:
Consider this to be a cross section from the wall of the urinary bladder, with the upper part being the inside of the wall and lower part being the inside of the wall and lower part being outside. The innermost layer is called the epithelium outer to which lies this layer called as lamina propria. Outer to lamina propria lies this layer, called an inner muscle layer. And on the outermost aspect lies the outer muscle layer.
So after discussing this normal anatomy of the bladder, let’s have a look at the T-staging for bladder cancer. TIS is the carcinoma in situ which is a flat tumor limited to the epithelium. Ans Ta is the papillary tumor which is limited to the epithelium. Both Tis and Ta are the non-invasive sub-types of bladder cancer. When the tumor infiltrates into the lamina propria it is called T1.
When it infiltrates into the inner muscle layer, it is called as T2a. And T2b when it infiltrates into the outer muscle layer. Till T2 the tumor is limited to the bladder wall, but when the tumor infiltrates through the bladder wall to involve the perivesical tissue it is called as T3 disease. And in T4 disease, the tumor infiltrates through the bladder wall to involve the adjacent structures. It may extend downwards to infiltrate prostate gland in male, as you can see in this figure.
Whereas in females, it may extend posteriorly to involve the uterus or vagina. It may also extend laterally to involve the pelvic or abdominal wall. This finishes the T staging for bladder cancer. Now, let’s come to the N staging or the nodal staging. This figure shows the pelvic and iliac group of lymph nodes which are the regional lymph nodes for the bladder. Depending upon the number and location of the lymph nodes involved, it can be N1, N2, or N3.
Now let’s come to the M staging or the metastatic staging for the bladder cancer st. Distant metastases from bladder cancer may occur to the bones. Or to the liver in the form of multiple nodular deposits.
It may also spread to one or both the lungs as seen in this figure. Or to the peritoneum in form of multiple peritoneal deposits. So with this, we come to the end of Bladder cancer TNM staging.