The bladder is an inflatable, hollow muscular organ situated in the pelvis. The main function of the bladder is to store urine until it is excreted from the body through the urethra. In a normal adult, it can hold up to 800 mL of urine.
The walls of urinary bladder consist of mainly three layers: mucosa (made up of transitional epithelium cells), lamina propria (made up of connective tissue), and muscularis propria (made up of 3 layers of smooth muscle fibers).
Read risk factors of bladder cancer.
Bladder Cancer Staging
Staging for bladder cancer is called as TNM staging system. It helps in disease prognostication and choosing an appropriate treatment strategy.
Stage 0 Bladder Cancer
Stage 0 bladder cancer includes cases of TaN0M0 and TisN0M0. This means Tis or Ta disease (as discussed below) without the involvement of regional nodes or distant spread of tumor.
The figure below shows the epithelium, that is the innermost layer of the bladder wall.
is the carcinoma in situ
which is a flat tumor limited to the epithelium.
is the papillary tumor
which is limited to the epithelium. Non-invasive papillary carcinoma also known as the papillary urothelial neoplasm of low malignant potential (PUNLMP)
Stage 1 Bladder Cancer
Stage 1 bladder cancer includes cases with T1N0M0 disease, that it T1 disease (as discussed below) without involvement of regional nodes or distant spread.
The layer of the bladder wall outside the epithelium is called as lamina propria, as shown in the figure below.
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.
Stage 2 Bladder Cancer
Stage 2 includes cases with T2N0M0 disease, that it T2 disease (as discussed below) without spread to regional lymph nodes or distant organs.
To understand it better, let’s see the layers of the bladder wall first. Outer to lamina propria lies this layer, called an inner muscle layer. And on the outermost aspect lies the outer muscle layer.
When bladder cancer infiltrates into the inner muscle layer, it is called as T2a.
when it infiltrates into the outer muscle layer
Stage 3 Bladder Cancer
Stage 3 tumor can be further classified into Stage 3a and Stage 3b.
Stage 3 includes cases of T3N0M0, T4aN0M0, T1-4aN1-3M0.
When the tumor infiltrates through the bladder wall to involve the perivesical tissue it is called as T3 disease. T3 disease without involvement of regional nodes or spread to distant organs is Stage 3a disease.
Also, when the bladder cancer extends outwards to involve the nearby structures, like prostate, uterus, vagina, or seminal vesicles (T4a disease), without spread to regional lymph nodes or distant sites, it comes under stage 3 disease.
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
Also, stage 3 bladder cancer includes cases of T1 to T4a disease (as discussed above), but with one or more regional lymph node positive (perivesical, obturator, internal or external iliac, sacral or common iliac lymph node).
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.
N1 – Involvement of one regional lymph node in true pelvis
N2 – Involvement of multiple regional lymph node in true pelvis
N3 – Involvement of common iliac lymph nodes
The involvement of any lymph node(s) by bladder cancer makes it stage 3 disease.
Stage 4 Bladder Cancer
Bladder cancer may also extend laterally to involve the pelvic or abdominal wall, as shown in the figure below. This is called as T4b disease, and is included in stage 4a baldder tumor.
also includes cases with tumor spread to lymph nodes beyond common iliacs (non-regional), like retroperitoneal, aortocaval, mediastinal nodes, etc (M1a
Stage 4b includes tumor spread to one or more distant organs such as lungs, bones, liver, peritoneum, etc (M1b).
Bladder cancer metastasis to distant sites largely depends on the extent of local infiltration, i.e. whether it is non-muscle invasive or muscle invasive. The muscle invasive bladder cancer has a higher likelihood of spread, owing to increased chances of cancer cells entering into systemic circulation. It also depends on the histology of bladder cancer, whether it is transitional cell or of atypical histology. Usually, atypical histology has a higher chance of distant metastasis.
The most common sites of metastasis
in decreasing order are lymph nodes, bone, lung, liver and peritoneum. The sites of metastasis is usually similar in different T stages, but in atypical histology tumors, peritoneal metastasis is more common than transitional cell histology.
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
4 Stages of Bladder Cancer
Based on the TNM staging discussed above, bladder cancer may be classified into 4 stages as mentioned below.
||Ta N0 M0
||Tis N0 M0
||T1 N0 M0
||T2a N0 M0 T2b N0 M0
||T3 N0 M0 T4a N0 M0 T1-4a N1 M0
||T1-4a N2-3 M0
||T4b Any N M0 Any T Any N M1a
||Any T Any N M1b
It is calculated based on whether the disease is Localised, Regional or Dstant.
- Cancer is limited to the bladder.
- 5 year survival 70%.
- Cancer has spread to nearby structures or lymph nodes
- 5 year survival 36%.
- Cancer has spread to distant body parts like lungs, liver or bones.
- 5 year survival 5%.