Transitional cell cancer of the renal pelvis and ureter is a rare form of cancer that develops in the lining of the upper urinary tract, where urine collects and flows from the kidneys to the bladder. This disease primarily affects older adults and shares many characteristics with bladder cancer, requiring careful diagnosis and treatment planning.
Understanding the Disease and How Common It Is
Transitional cell cancer of the renal pelvis and ureter is an uncommon disease that develops in the specialized cells lining parts of the urinary system. These cells, called transitional cells or urothelial cells, have a remarkable ability to stretch when the kidney or bladder fills with urine and shrink when emptied. The renal pelvis is the hollow area at the center of each kidney where urine collects before flowing into the ureters, which are the tubes connecting the kidneys to the bladder.[1]
This type of cancer represents only a small fraction of all kidney tumors. Transitional cell cancer of the renal pelvis accounts for approximately 7% of all kidney tumors, while cancer of the ureter is even less common, making up only about 4% of upper urinary tract tumors. Together, these cancers constitute roughly 10% of all transitional cell cancers, with the remaining 90% occurring in the bladder.[2]
The disease typically affects adults ages 65 and older, making age a significant factor in its occurrence. Men are diagnosed more frequently than women, with males being approximately four times more likely to develop bladder cancer and twice as likely to develop kidney cancers of this type. Despite its rarity, evidence suggests that the frequency of upper urinary tract malignancies may be increasing in recent years.[1][6]
More than 90% of cancers occurring in the renal pelvis and ureter arise from transitional cells, which is why this disease is also called urothelial carcinoma. The predominant pattern is a papillary tumor with stratified, non-keratinizing cells supported on a thin core. These upper tract cancers are histologically identical to bladder cancer, meaning they look the same under a microscope and behave similarly.[4][6]
What Causes This Cancer
The exact cause of transitional cell cancer of the renal pelvis and ureter remains unknown to doctors and researchers. However, the disease develops when healthy transitional cells in the renal pelvis or ureter undergo certain changes that affect how they function, particularly how they grow and divide into new cells. These cellular changes, called mutations, cause a normal cell to become cancerous and begin growing uncontrollably.[3]
While the precise trigger for these mutations is unclear, both genetic and environmental factors appear to play important roles. The disease is not caused by a single factor but rather emerges from a combination of influences that damage the cells lining the urinary tract over time. The cancer cells can form tumors that disrupt normal urine flow, cause bleeding, and lead to blockages in the urinary system.[1]
Because these upper tract cancers come from the same type of cells that line the bladder, they share common risk factors and can occur as part of what doctors call “field cancerization.” This means that exposure of the entire urothelium to substances excreted or activated in urine can lead to cancer at multiple sites. As a result, upper urinary tract tumors may be multifocal, appearing in more than one location, and in 2% to 10% of cases, they occur on both sides of the body.[6]
The connection between bladder cancer and upper tract cancer is particularly strong. Bladder tumors develop in 20% to 48% of patients who have upper urinary tract cancer, usually appearing within five years. Similarly, upper urinary tract cancer develops in 2% to 4% of patients who already have bladder cancer, with the risk rising to as high as 21% in those with certain types of bladder disease or occupational exposures.[6]
Who Is at Higher Risk
Several factors increase a person’s likelihood of developing transitional cell cancer of the renal pelvis and ureter. Understanding these risk factors can help individuals and their doctors remain vigilant for early signs of disease, though having one or more risk factors does not guarantee that cancer will develop.[3]
Cigarette smoking stands out as the most significant acquired risk factor for upper urinary tract cancer. Research suggests that approximately 70% of upper urinary tract urothelial tumors in men and 40% in women can be attributed to smoking. The harmful chemicals in tobacco smoke are filtered through the kidneys and collect in the urinary tract, where they can damage the delicate lining cells over extended periods.[6]
A personal history of bladder cancer significantly increases risk for developing cancer in the renal pelvis or ureter. This connection reflects the shared nature of the cells lining the entire urinary tract. When one area develops cancer, other areas remain vulnerable to similar changes.[1][3]
Occupational exposures to certain chemicals also raise risk substantially. Workers in the chemical, petrochemical, aniline dye, and plastics industries face increased risk, as do those exposed to coal, coke, tar, and asphalt. People who work with chemicals and dyes used in manufacturing plastics, rubber, printed materials, leather goods, and hairdressing supplies may also have elevated risk.[1][6]
Lynch syndrome, an inherited genetic condition that increases the risk of several types of cancer, also raises the likelihood of developing transitional cell cancer of the upper urinary tract. This syndrome affects how cells repair DNA damage, making cancer more likely to develop in affected individuals.[1]
Two chronic kidney disorders—Balkan endemic nephropathy and Chinese herbs nephropathy—have also been linked to increased risk of upper urinary tract tumors. Both conditions involve long-term damage to kidney tissue that can predispose the urinary tract lining to cancerous changes.[6]
Recognizing the Symptoms
Symptoms of transitional cell cancer of the renal pelvis and ureter may not appear immediately, which can delay diagnosis. The most common and often first noticeable symptom is blood in the urine, a condition called hematuria. This blood may be visible to the naked eye, making the urine appear pink, red, or cola-colored, or it may only be detectable under a microscope during routine testing.[1][7]
Back pain is another frequent symptom, particularly discomfort in the area between the ribs and hips on one side of the body, known as the flank. Some people experience persistent cramps in the side or back that do not go away with rest or simple pain relievers. This pain occurs because the growing tumor can obstruct urine flow or stretch the tissues surrounding the kidney or ureter.[1]
Fatigue is a common but non-specific symptom that many patients experience. This overwhelming tiredness does not improve with rest and can significantly affect daily activities. Unexplained weight loss may also occur as the cancer progresses, reflecting the body’s changing metabolism and the energy demands of the disease.[1]
Some individuals develop pain or a burning sensation when urinating, and others notice they need to urinate more frequently than usual. These symptoms occur when the cancer affects the normal function of the urinary tract or causes irritation to surrounding tissues. In some cases, a lump or mass may be felt in the kidney area, though this is less common.[1][7]
It is important to note that these symptoms can also be caused by conditions other than cancer, such as kidney stones, infections, or benign growths. However, anyone experiencing blood in their urine or persistent back pain should contact a healthcare provider promptly for evaluation. Early detection significantly improves treatment outcomes.[7]
Prevention Strategies
While there is no guaranteed way to prevent transitional cell cancer of the renal pelvis and ureter, certain lifestyle choices and preventive measures may reduce risk. The most impactful step a person can take is to avoid smoking or quit if they currently smoke. Because smoking is responsible for the majority of these cancers, eliminating tobacco use substantially lowers risk and benefits overall health in numerous other ways.[6]
People who work in industries with known chemical exposures should take appropriate safety precautions. This includes using protective equipment, following workplace safety guidelines, and minimizing direct contact with harmful substances. Employers in high-risk industries should provide proper ventilation and protective measures to reduce workers’ exposure to carcinogenic chemicals.[1]
For individuals with a personal history of bladder cancer, regular follow-up care and monitoring are essential. These patients have an elevated risk of developing cancer in the upper urinary tract and should work with their healthcare team to establish an appropriate surveillance schedule. Similarly, people with Lynch syndrome should undergo genetic counseling and may benefit from more frequent screening.[1]
Maintaining good overall health through a balanced diet, regular physical activity, and adequate hydration supports kidney function and may contribute to a healthier urinary system. While these measures have not been specifically proven to prevent upper urinary tract cancer, they support general well-being and reduce the risk of many other diseases.[7]
How the Disease Affects the Body
Understanding how transitional cell cancer disrupts normal body functions helps explain the symptoms patients experience and why treatment is necessary. In a healthy urinary system, the kidneys continuously filter blood to remove waste products and excess water, producing urine. This urine collects in the renal pelvis at the center of each kidney before draining through the ureters into the bladder, where it is stored until urination.[3]
The walls of the renal pelvis and ureters are composed of several layers. The innermost layer, called the urothelium, is made up of transitional cells that can stretch and change shape as urine flows through. Beneath this lies the lamina propria, a thin layer of connective tissue containing blood vessels, nerves, and glands. The outer layer, called the muscularis propria, consists of smooth muscle that contracts automatically to push urine from the kidney down to the bladder.[4]
When cancer develops, the normal flat lining of transitional cells begins to grow in an uncontrolled manner, forming masses or tumors. These tumors can take on a papillary pattern, growing outward into the hollow space where urine flows, or they can invade deeper into the wall of the renal pelvis or ureter. As tumors grow, they disrupt the smooth flow of urine through the urinary tract.[1]
Blockages caused by tumors can prevent urine from draining properly, leading to a backup of urine in the kidney. This obstruction can cause the kidney to swell, a condition called hydronephrosis, which produces pain and can damage kidney function if left untreated. The tumors are often fragile and bleed easily, which explains why blood in the urine is such a common symptom.[1]
The major prognostic factor in this disease is how deeply the cancer has infiltrated into or through the wall of the renal pelvis or ureter. Superficial tumors that remain on the surface of the inner lining are usually well-differentiated, meaning the cancer cells still resemble normal cells to some degree. These tumors tend to be less aggressive and have better outcomes.[2]
Invasive tumors that penetrate deeply through the layers of the urinary tract wall are more likely to be poorly differentiated, with cells that look very abnormal under the microscope. These aggressive tumors have a higher likelihood of spreading beyond the original site. Grade and stage of the tumor correlate closely—superficial tumors are generally low-grade (grades I or II), while infiltrative tumors are typically high-grade (grades III and IV).[17]
Without treatment, cancer cells can break away from the original tumor and spread to nearby lymph nodes or distant organs through the bloodstream or lymphatic system. Common sites of spread include the bladder, lungs, liver, and bones. The likelihood of the cancer spreading depends on its depth of invasion and grade at the time of diagnosis.[2]
Cancers that are superficial and confined to the renal pelvis or ureter are curable in more than 90% of patients when detected early and treated appropriately. However, patients with deeply invasive tumors confined to these areas have only a 10% to 15% likelihood of cure. Those with tumors that have penetrated through the wall or spread to distant sites usually cannot be cured with currently available treatments, though therapies can help manage symptoms and extend life.[2]
The cancer can also affect kidney function directly. When a tumor obstructs urine flow or when treatment requires removal of a kidney, the body’s ability to filter waste products may be compromised. In most cases, a single healthy kidney can perform adequately for the body’s needs, but pre-existing kidney disease or bilateral involvement can complicate treatment decisions and outcomes.[14]
