Metastatic transitional cell carcinoma is an advanced form of cancer that begins in the cells lining the urinary system and spreads to other parts of the body. Understanding this condition, its patterns, and how it affects people can help patients and families navigate a challenging diagnosis with greater knowledge and support.

Epidemiology

Transitional cell carcinoma, also called urothelial carcinoma, is a type of cancer that starts in the special cells lining the inside of the urinary system. These cells, called transitional cells or urothelial cells, are found in the bladder, the renal pelvis (the central part of the kidney where urine collects), and the ureters (the tubes that carry urine from the kidneys to the bladder). These remarkable cells can stretch when the bladder fills with urine and shrink when it empties.^[1]

This type of cancer is relatively uncommon when it occurs in the upper urinary tract. Transitional cell cancer of the renal pelvis accounts for only about 7% of all kidney tumors. Cancer of the ureter is even rarer, making up only about 4% of upper urinary tract tumors.^[6] In contrast, transitional cell carcinoma is much more common in the bladder, where it accounts for about 90% of all bladder cancer cases in the United States.^[3]

Between 5% and 10% of people with urothelial cancer already have metastatic disease at the time of diagnosis. This means the cancer has spread beyond its original location to other parts of the body.^[13] Approximately 10% to 15% of patients are diagnosed at the advanced stage IV, when the cancer has already metastasized.^[23]

Gender plays a significant role in who develops this disease. Men are four times more likely to develop bladder cancer and are also twice as likely to develop kidney cancers compared to women.^[3] Upper urinary tract urothelial cancer is diagnosed more often in men than in women overall.^[4]

Age is another important factor. Most people diagnosed with this type of cancer are over the age of 65.^[3] The disease is more common in older people, reflecting how cancer risk generally increases as we age.^[4]

Race also appears to influence risk, though the reasons are not fully understood. Caucasian men may be at greater risk for developing bladder cancer.^[1]

Causes

Medical researchers do not know exactly what causes transitional cell carcinoma to develop and spread. However, they do understand that it involves changes in how specific cells in the urinary system function. A healthy transitional cell undergoes a change, or mutation, that transforms it into a cancer cell. These cancer cells can then form tumors. Without treatment, the cancer can spread from its original location to other parts of the body.^[3]

The process that leads a normal cell to become cancerous involves changes in how the cells grow and divide. In transitional cell cancer, certain changes occur in the way transitional cells in the renal pelvis and ureters function, particularly affecting how they grow and create new cells.^[1]

When transitional cell cancer becomes metastatic, it means the cancer cells have traveled from the bladder, kidney, or ureter to other organs. The cancer typically spreads to the pelvic lymph nodes first, and then to distant sites including the lungs, liver, and bones. In some cases, especially after patients have received systemic chemotherapy, the cancer can also spread to the brain.^[2]

In rare instances, the cancer can spread to unusual locations. One documented case described a patient whose transitional cell carcinoma from the bladder had metastasized to the soft tissue of the shoulder girdle, an extremely uncommon site for this type of cancer.^[2]

Risk Factors

Several factors can increase a person’s risk of developing transitional cell carcinoma. Understanding these risk factors can help people recognize their potential vulnerability to the disease, though having one or more risk factors does not guarantee that someone will develop cancer.

Smoking is one of the most significant risk factors. Cigarette smoking increases the risk of urothelial carcinoma substantially. People who smoke may be up to four times more likely to develop bladder cancer compared to non-smokers.^[3] This is because harmful chemicals from tobacco smoke are filtered through the kidneys and concentrated in the urine, exposing the lining of the urinary system to these cancer-causing substances.

A personal history of bladder cancer significantly increases the risk of developing transitional cell cancer in the renal pelvis and ureters. People who have had bladder cancer are at increased risk for developing cancer in other parts of the urinary tract.^[1] In fact, after someone has had transitional cell cancer in the upper urinary tract, the likelihood of developing subsequent bladder cancer ranges from 30% to 50%. When the upper tract cancer involves both the renal pelvis and the ureter, the risk of later bladder cancer increases to 75%.^[6]

Exposure to specific substances can also increase risk. Aristolochic acid, produced by aristolochia plants, may be found in some herbal remedies and can cause kidney damage and increase cancer risk.^[4] Exposure to radiation and certain chemotherapy drugs, such as cyclophosphamide, have also been linked to bladder cancer.^[23]

Certain genetic conditions raise the risk as well. Lynch syndrome, an inherited condition, increases the risk of several cancers, including urothelial cancer.^[4]

However, many people develop bladder cancer for no known reason. A significant number of patients never had any identifiable risk factors, which can be frustrating for those trying to understand why they developed the disease.^[23]

Symptoms

The symptoms of metastatic transitional cell carcinoma can vary depending on where the cancer has spread, but there are common signs that often appear first. Recognizing these symptoms and seeking medical attention promptly can be crucial.

Blood in the urine, called hematuria, is usually the first noticeable sign of transitional cell carcinoma. This may appear as pink, red, or cola-colored urine. Sometimes the blood is visible to the naked eye, while other times it can only be detected through laboratory testing. The bleeding is typically painless, which distinguishes it from bleeding caused by infections.^[3]

Pain can occur in different locations. Some people experience pain in their side, between the ribs and the hip, an area called the flank. This type of pain may indicate that the cancer is affecting the kidney or ureter.^[4] Others may have persistent low back pain or painful urination.^[3]

Changes in urination patterns are common. People may need to urinate more frequently than usual or feel an urgent need to urinate. These symptoms can sometimes be mistaken for a urinary tract infection, which is why proper testing is important.^[3]

General symptoms that affect overall health can also occur. Many patients experience significant fatigue that does not improve with rest. Unexplained weight loss, where a person loses weight without trying, is another concerning sign. Some people may feel a lump or mass in their kidney area, located on the side and back between the ribs and hips.^[3]

When the cancer has metastasized, symptoms may appear related to where it has spread. If the cancer has reached the bones, patients may experience bone pain. When it spreads to the lungs, breathing problems or persistent cough may develop. Spread to the liver can cause abdominal discomfort or jaundice (yellowing of the skin and eyes).^[2]

In one documented case, a patient with metastatic transitional cell carcinoma developed right shoulder and neck pain, with a palpable soft tissue mass in the posterior shoulder. This unusual presentation led to the discovery of cancer that had spread to multiple bones throughout the body.^[2]

Sometimes, symptoms may not appear right away or may be subtle and easily overlooked. In some cases, upper urinary tract urothelial cancer is discovered incidentally when a person is having a scan or test for an unrelated medical reason.^[4]

Prevention

While there is no guaranteed way to prevent transitional cell carcinoma, certain lifestyle choices and actions can help reduce the risk of developing this disease.

Not smoking is the single most important preventive step a person can take. Since smoking is one of the leading risk factors for transitional cell carcinoma, avoiding tobacco or quitting if you currently smoke can significantly lower your risk. For people who do smoke, cessation programs and support systems are available to help them quit.^[3]

Workplace safety is another important consideration. People who work with chemicals known to increase cancer risk should take all recommended precautions. This includes using proper protective equipment, following safety protocols, ensuring good ventilation, and minimizing direct exposure to harmful substances. If you work in an industry that involves dyes, rubber, leather, paint, textiles, or hairdressing supplies, talk to your employer about safety measures and consider regular health screenings.^[3]

Being cautious about herbal remedies is also wise. Some supplements may contain aristolochic acid, which can cause kidney damage and increase cancer risk. Always discuss any herbal products or supplements with your healthcare provider before using them.^[4]

For people who have had bladder cancer, close monitoring and regular follow-up care are essential. Since a history of bladder cancer increases the risk of developing transitional cell cancer in the upper urinary tract, these individuals should maintain regular contact with their healthcare providers and report any new symptoms promptly.^[3]

Understanding your family history can also be helpful. If you have Lynch syndrome or other genetic conditions that increase cancer risk, discuss screening options and preventive strategies with your doctor. Early detection through appropriate monitoring can make a significant difference in outcomes.^[4]

Pathophysiology

Understanding how metastatic transitional cell carcinoma develops and progresses involves looking at the changes that occur at the cellular and tissue level in the body.

The urinary system is lined with specialized transitional cells, also called urothelial cells. These cells have a unique ability to change shape. They can stretch and expand when the bladder fills with urine, and then collapse and shrink when the bladder empties. This flexibility is essential for the normal function of the urinary system. These transitional cells line the renal pelvis in the kidney, the ureters that connect the kidneys to the bladder, the bladder itself, and the urethra through which urine leaves the body.^[1]

When transitional cell carcinoma develops, genetic changes occur in these cells that cause them to grow and divide abnormally. Instead of following the normal cell life cycle of growth, division, and eventual death, cancer cells continue to multiply without stopping. They lose their specialized functions and their ability to respond to normal growth control signals in the body.^[1]

The depth of cancer invasion into the urinary tract wall is one of the most important factors determining how the disease will progress. Cancers are classified based on how deeply they have grown into the tissue layers. Superficial tumors remain on the inner surface of the urinary tract lining and have not invaded deeper layers. These cancers are generally well-differentiated, meaning the cells still look somewhat similar to normal cells and tend to grow more slowly.^[6]

Invasive tumors, on the other hand, have grown into or through the deeper layers of the urinary tract wall. These cancers are often poorly differentiated, meaning the cells look very different from normal cells and tend to be more aggressive. The more deeply a tumor invades, the worse the prognosis tends to be.^[6]

Most upper tract urothelial tumors are of transitional cell type, but less commonly, other types can occur. Squamous cell cancer makes up less than 15% of tumors of the renal pelvis and an even smaller percentage of ureteral tumors. This type is often associated with chronic kidney stones and long-term infection.^[6]

The grade of the cancer also matters. Cancer cells are examined under a microscope and assigned a grade based on how abnormal they appear. Low-grade tumors (grades I and II) have cells that look relatively similar to normal cells, while high-grade tumors (grades III and IV) have cells that look very abnormal. Generally, superficial tumors tend to be low-grade, while invasive tumors are more likely to be high-grade.^[6]

As transitional cell carcinoma progresses to the metastatic stage, cancer cells break away from the original tumor and travel through the body. They can spread through the lymphatic system, which is the network of vessels and nodes that helps fight infection. The cancer often first reaches the pelvic lymph nodes, which are located near the bladder and lower urinary tract.^[2]

Cancer cells can also enter the bloodstream and travel to distant organs, establishing new tumors at these sites. The most common places for metastatic transitional cell carcinoma to spread are the lungs, liver, and bones. After treatment with chemotherapy, the brain can also become a site of metastasis.^[2]

There is also a pattern of cancer recurrence in different parts of the urinary tract. When someone has had transitional cell cancer in the upper urinary tract, they have a 2% to 4% chance of developing cancer in the opposite kidney or ureter. The risk of developing bladder cancer after having upper tract cancer is much higher, ranging from 30% to 50%.^[6]

The behavior of metastatic transitional cell carcinoma reflects the aggressive nature of the disease at this advanced stage. The cancer has demonstrated its ability to invade deeply, break away from its original location, survive in the bloodstream or lymphatic system, and establish new growth in different organs. This spread makes treatment more complex and challenging, as the cancer is no longer confined to one area that can be surgically removed.^[6]