Bladder cancer occurs when cells in the lining of the bladder grow uncontrollably and form tumors that can invade normal tissues and spread to other parts of the body.
Cancers are described by the types of cells from which they arise. Bladder cancers arise almost exclusively from the lining of the bladder. In the United States, 98% of bladder cancers are called transitional cell carcinomas. This simply means that the cancer started in the lining of the bladder, which is made up of transitional cells that appear elliptical under the microscope. Less commonly are other types of cancers that arise from the lining of the bladder, called adenocarcinomas, squamous cell carcinomas and small cell carcinomas. A common way for bladder cancers to grow is called a papillary growth pattern. When a bladder cancer grows this way, it can be noninvasive, i.e., not invading into tissues at all, and hence not having a risk for distant spread (as long as it is treated). In addition to other invasive cancers, patients are sometimes diagnosed with precancerous lesions, called carcinoma-in-situ. Carcinoma-in-situ occurs when the lining of the bladder undergoes changes similar to can cerous changes without any invasion into the deeper tissues. Hence, while the cells themselves have cancer-like qualities, there is no risk of spread, as no invasion has occurred. However, both papillary bladder cancers and cancer-in-situ may become invasive and cause problems if not treated.
How is bladder cancer diagnosed and staged?
Anyone with either gross or microscopic hematuria should undergo a work-up to insure the symptoms are not from bladder cancer. Often, the first thing that is done is a urine cytology, which as mentioned above, is looking at the urine under a microscope to detect cancerous appearing cells. Again, if these cells are seen, it is diagnostic. However, the test does not detect all cases of bladder cancer. If bladder cancer is highly suspected, or after diagnosis, an X-ray imaging of the upper urinary tract (including the ureters and kidneys) is done, to rule out any involvement of these structures with cancer. Ultrasound can be used to study the kidneys and a CT scan is often very good at studying the entire length of the urinary tract. A simpler method of studying the (upper) urinary tract is with an intravenous pyelogram (IVP). This involves administering a dye through a patient's vein and taking a regular x-ray a short time later. The dye can be seen in the x-ray, showing the full extent of the kidney collecting system, ureters, and often the bladder.
Though the above tests are useful or even required, the mainstay of diagnosis and staging is endoscopic evaluation. In this case, this type of evaluation is called a cystoscopy. It involves placing a fiber optic camera into the bladder via the urethra. Cystoscopy allows for direct visualization of the entire bladder and also allows for biopsy for any suspicious lesions. If the biopsy reveals cancer, a repeat cystoscopy and resection (called a transurethral resection (TUR)) is done to completely evaluate the tumor and the extent and depth of disease.
With a diagnosis of bladder cancer obtained, a complete physical examination is done as well as the previously mentioned radiological studies to fully evaluate the urinary tract, the local extent of disease, and any metastasis disease.
The staging of a cancer basically describes how much it has grown before the diagnosis has been made, documenting the extent of disease. Bladder cancer often presents at an early stage, as it produces hematuria early on in the course of the disease. Unfortunately, sometimes bladder cancer can advance to invasive disease prior to causing symptoms. As will be discussed in the treatment section, a big distinction is whether the bladder cancer is superficial or invading into the muscle, because the treatments are much different. Before the staging systems are introduced, first some background on how cancers grow and spread, and therefore advance in stage.
Cancers cause problems because they spread and can disrupt the functioning of normal organs. Bladder cancers often start very superficial, involving only the lining of the bladder. Eventually, however, bladder cancers can invade into the bladder, involving the muscular layers of the wall. If the bladder cancer is allowed to grow long enough or is aggressive enough, it may eventually invade the entire way through the wall and into the fat surrounding the bladder or even into other organs (prostate, uterus, and vagina). This local extension is the most common way bladder cancer spreads.
Cancer can also spread by accessing the lymphatic system. The lymphatic circulation is a complete circulation system in the body (somewhat like the blood circulatory system) that drains into various lymph nodes. When cancer cells access this lymphatic circulation, they can travel to lymph nodes and start new sites of cancer. This is called lymphatic spread. Bladder cancer can spread this way. If it does, it usually first spreads to the lymph nodes while surrounding the bladder (perivascular lymph nodes). From there, it can spread to lymph nodes that are in close proximity to the external iliac and internal iliac arteries and veins, which are the very large blood vessels that run into the leg and into the pelvis, respectively. The presence of lymph node spread is best evaluated by CT scan or at surgical exploration.
Bladder cancer can also spread through the bloodstream. Cancer cells gain access to distant organs via the bloodstream and the tumors that arise from cells traveling to other organs are called metastases. Cancers of the bladder generally spread locally or to lymph nodes before spreading distantly through the bloodstream, though this is not always the case. If spread through the bloodstream does occur, the lungs and bones are the most common sites to be involved.
The staging system used to describe bladder tumors is the "TNM system", as described by the American Joint Committee on Cancer. The TNM systems are used to describe many types of cancers. They have three components: T-describing the extent of the "primary" tumor (the tumor in the bladder itself); N-describing the spread to the lymph nodes positive for metastatic disease, if any; M-describing the spread to other organs (i.e.-metastases).
There are two "T" stages that are often reported: the clinical stage, which is based on the physical exam of the physician, and the pathologic stage, which is noted after the tumor is rejected, or taken out surgically.
- T1-Physician feels nothing on exam prior to transurethral resection (TUR)
- T2-Physician feels nothing on exam after TUR
- T3a-Any visually incomplete TUR or persistent tumor felt after TUR
- T3b-Any tumor that extends beyond bladder on exam
- T4-Tumor that involves other organs
- Ta-noninvasive papillary tumor
- Tis-carcinoma-in-situ (explained above)
- T1-tumor invading the mucosa (lining of bladder)
- Above are considered "superficial"
- T2-tumor invades superficially into muscle of wall
- T3a-tumor invades deeply into muscle of the bladder wall
- T3b-tumor invades the entire way through the wall
- T4-tumor invades other organs
The "N" stage is as follows:
- N0-no spread to lymph nodes
- N1-tumor spread to a single lymph node, but this tumor spread must be less than 2 cm
- N2-tumor spread to lymph nodes sized 2-5 cm
- N3-tumor spread to lymph nodes greater than 5 cm
The "M" stage is as follows:
- M0-no tumor spread to other organs (or sites)
- M1-tumor spread to other organs, sites
The overall stage is based on a combination of these T, N, and M parameters. Though complicated, these staging systems help physicians determine the extent of the cancer, and therefore make treatment decisions regarding a patient's cancer. The stage of cancer, or extent of disease, is based on information gathered through the various tests done as the diagnosis and work-up of the cancer is being performed. An important distinction in bladder cancer is between superficial disease (Ta, Tis, and T1) or muscular invasive disease. It has large implications for treatment, as will be discussed below.