Bladder cancer staging and grading are the two systems doctors use to determine how far a tumour has spread and how quickly its cells are likely to grow. Staging uses the Tumour, Node, Metastasis (TNM) system and is often expressed as Stage 0 through Stage IV, while grading classifies tumour cells as low-grade or high-grade based on how abnormal they appear under a microscope. Bladder cancer also presents differently in every patient, and identifying the tumour’s type, shape, stage, and grade helps determines the treatment strategy. After a tumour is removed, doctors assign each of these classifications to guide the course of action and treatment options.
Types of Bladder Cancer Tumours, Stages & Grades
Types of Bladder Cancer Tumours
Your cancer’s cell type, also called histological type, refers to what the cell structure looks like under the microscope and how the cells are arranged.
Bladder cancer includes many histological types:
- Transitional cell carcinoma is the most common bladder cancer type and accounts for about 90% of bladder cancers.
- Squamous cell carcinoma is cancer that begins in the thin, flat cells lining the inside of the bladder.
- Adenocarcinoma is cancer that begins in glandular cells that are found in the lining of the bladder. Glandular cells in the bladder make mucus and other substances.
- Small cell carcinoma starts in nerve-like cells called neuroendocrine cells. Less than 1% of bladder cancers are small cell carcinomas which includes neuroendocrine, micropapillary and mixed-pattern subtypes.
- Sarcomatoid/plasmacytoid is an extremely rare aggressive tumour variant comprising about 0.3% of all primary bladder cancer.
Shapes of Bladder Cancer Tumours
Some types of bladder cancer tumours are classified based on their shape. The shape of your tumour can indicate how serious and aggressive the cancer may be.
- Papillary tumours have long, finger-like projections that stretch out from the bladder wall toward your bladder’s interior.
- Sessile tumours lie flat and are superficial tumours that may grow deeper into the bladder wall.
- Carcinoma in situ (CIS) or a “flat tumour” is only found on or near the surface of the bladder. The doctor may also call it non-muscle invasive bladder cancer, superficial bladder cancer, or non-invasive flat carcinoma. This type of bladder cancer often comes back after treatment, usually as another non-invasive cancer in the bladder.
Staging & Grading of Bladder Cancer Tumours
Upon diagnosis of bladder cancer, it is imperative for the doctor to determine the stage or extent of the disease.
Laboratory analysis of the material taken out during a Transurethral Resection of Bladder Tumour (TURBT) is used to determine the stage and grade of the cancer.
The urologist typically sends a sample of the cancer tissue to a pathologist, a doctor who specializes in examining tissue. Upon review of the subsequent pathology report, the doctor will determine an optimal treatment plan.
Staging involves assessing whether the cancer has penetrated the bladder wall and if the disease has metastasized or spread, and if so, to which areas of the body.
Grade, on the other hand, pertains to the appearance of cancer cells and their rate of multiplication. A higher grade indicates greater cellular irregularity and proliferation. Grade is typically reported simply as low-grade or high-grade, and pathologists often write stage and grade together on a report. Understanding the grade aids the doctor in predicting the pace at which the bladder cancer will progress and spread.
Staging is generally described using the TNM system, which evaluates the primary Tumour (T), whether cancer has spread to nearby lymph Nodes (N), and whether it has Metastasized (M) to distant parts of the body; together these factors are often summarized as Stage 0 through Stage IV.
What Bladder Cancer Stages & Grades Mean
Tis – Carcinoma in situ (flat tumour), sometimes called Cis. This is classified as Stage 0.
Ta – Non-invasive papillary carcinoma. This is also classified as Stage 0.
T1 – The tumour is in the first layer of the bladder lining, but not the surrounding muscle. This corresponds to Stage I.
T2 – The tumour has grown into the muscle. In stage T2a, the tumour is in the inner half of the muscle layer and in stage T2b, the outer half. This corresponds to Stage II.
T3 – The tumour has spread to the fatty layer around the bladder muscle. T3a describes a microscopic tumour and T3b a large tumour that can be seen or felt. This corresponds to Stage III.
T4 – The tumour has spread to organs outside the bladder (T4a) or to the wall of the abdomen or pelvis (T4b). This corresponds to Stage IV, particularly when lymph node involvement (N) or distant metastasis (M) is also present.
Staging Bladder Cancer
Sometimes it may be difficult for your medical team to know the true extent of your tumour without surgery because there may be a difference between “clinical staging” and “pathological staging.”
The resection of the tumour or TURBT is part of the clinical staging process, which is done before treatment. Clinical staging also includes a physical exam, imaging tests (such as a CT scan), laboratory tests (such as blood tests), and biopsies.
Cancer can be further staged by examining the material removed during a radical cystectomy (bladder removal). This process is called pathologic staging. Complete staging combines the results of the clinical staging with the surgical results. If bladder removal is not recommended or you choose not to have your bladder removed, the medical team will determine the stage through the initial resection or clinical staging process.
Grading Bladder Cancer
The pathology report that follows the TURBT will generally show whether the tumour is “high grade” or “low grade.” A diagnosis of muscle-invasive bladder cancer may be based on the finding of high-grade tumours. If possible, keep a copy of the pathology report, which will tell you the stage and grade of your tumour.
- Low-grade tumours grow slowly and rarely invade other tissues or spread to other parts of the body.
- High-grade tumours are more likely to recur and may become invasive. These tumours contain cells that grow abnormally and can invade other tissues and spread to other parts of the body.
Illustration Credit: Zuzanna Gorski, Mypathologyreport.ca
There are many types and shapes of bladder cancer tumours that are identified after the tumours are removed for laboratory analysis. Determining the type and shape of a tumour helps doctors to know how to treat the bladder cancer.
Why Stage and Grade Matter for Treatment Planning
Stage and grade are the two factors your care team weighs most heavily when deciding on a treatment path, because each answers a different question. Stage tells the team how far the cancer has physically progressed and whether the priority is removing a contained tumour or addressing disease that has spread. Grade tells the team how the cancer is likely to behave over time and how closely follow-up and surveillance need to be managed, even after a tumour is removed.
Generally, non-muscle-invasive cancers (Stage 0-I) are often treated through TURBT alone or TURBT combined with intravesical therapies like BCG, with the grade determining how often follow-up cystoscopies are needed. Muscle-invasive and advanced cancers (Stage II-IV) more often require a combination of approaches, which may include chemotherapy and radiation, bladder removal surgery, or immunotherapy. Your urologist will use your specific stage and grade together to recommend the most appropriate path forward.
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