Renal adenoma is a small, usually noncancerous growth in the kidney, and many people have no symptoms at all. Many people first hear about renal adenoma after a scan done for another reason, because the early symptoms of renal adenoma are often absent or very mild. When symptoms do happen, they can include blood in the urine, side or back discomfort, or a kidney mass found on imaging. Renal adenoma is most often found in adults, may stay stable for a long time, and it is not usually linked to death by itself. Treatment for renal adenoma may involve watching it over time with scans or removing it if it is growing, causing symptoms, or looks too much like kidney cancer.
How many people live with Renal adenoma?
For renal adenoma, a small noncancerous growth in the kidney, global and U.S. population estimates are not consistently reported by a single authoritative source. This is mainly because it is often found by chance and has not been routinely tracked in a way that allows a reliable worldwide or U.S. count.
Overview
Renal adenomaSymptoms
Renal adenoma usually causes no symptoms and is often found by chance on imaging. If it grows or bleeds, some people may notice blood in the urine, side or back pain, or a lump near the kidney.
Outlook and prognosis
Renal adenoma usually has an excellent outlook. These small kidney growths often stay harmless and are often found by chance on imaging. Prognosis depends mainly on size and whether doctors are concerned it could actually be an early kidney cancer.
Causes and risk factors
The exact cause of renal adenoma is unclear. Risk appears to rise with older age and may be higher in people who smoke or live with obesity, high blood pressure, or long-term kidney disease.
Genetic influences
Genetics are not thought to play a major role in most renal adenoma cases. Unlike some kidney tumors, inherited gene changes have not been clearly linked, though research is still ongoing.
Diagnosis
Renal adenoma is usually found on imaging tests such as ultrasound, CT, or MRI, often when checking something else. Diagnosis of renal adenoma may need follow-up scans and sometimes a biopsy to rule out kidney cancer.
Treatment and drugs
Renal adenoma is often managed with regular imaging to watch for growth or changes. If it causes symptoms, gets larger, or looks uncertain on scans, surgery may be recommended. Care depends on the tumor’s size, location, and your overall kidney health.
Symptoms
Many people with renal adenoma feel completely well, and the growth is often found by chance during an ultrasound or CT scan done for another reason. When symptoms do happen, they usually overlap with those of other kidney growths, so renal adenoma cannot be recognized by symptoms alone. A healthcare professional can help sort out what’s typical aging and what warrants a closer look.
The early symptoms of renal adenoma are often absent, especially when the growth is small. Many people only learn it is there after imaging for kidney stones, back pain, or another unrelated issue.
Some people notice pink, red, or tea-colored urine if the growth irritates nearby kidney tissue. Even a small amount of blood in the urine should be checked because the same symptom can happen with infections, stones, or kidney cancer.
A dull ache in the flank, the area between the ribs and hip, can happen if the growth stretches tissue around the kidney. The pain is not specific, so it can be mistaken for a muscle strain or another kidney problem.
Less often, a larger kidney growth may cause pressure, fullness, or a lump in the side or upper abdomen. This is uncommon with renal adenoma because these growths are often very small.
How people usually first notice Renal adenoma?
Renal adenoma is usually first noticed by chance, when a scan such as an ultrasound, CT, or MRI is done for another reason and shows a small growth in the kidney. Most people with renal adenoma do not feel anything at all, but when symptoms do happen, the first signs can include blood in the urine, flank or back pain, or less often a lump your doctor can feel. Because these symptoms can also happen with other kidney conditions, including kidney cancer, doctors usually follow up with more imaging and sometimes other tests to find out exactly what the growth is.
Types of Renal adenoma
Renal adenoma usually means a small, noncancerous growth in the kidney. In everyday care, the types of renal adenoma are not as clearly separated as they are for some other conditions, and many are found by chance during a scan done for something else. When doctors do divide them, they usually mean different cell patterns seen under the microscope, which can affect how likely symptoms are to show up or how closely the growth may resemble a small kidney cancer on imaging. Symptoms don’t always look the same for everyone.
Papillary adenoma
This is the most common type linked with the term renal adenoma, and it is usually very small. Most people have no symptoms, but a larger growth may rarely be associated with blood in the urine or a dull ache in the side. In many cases, it is found incidentally during imaging or after surgery for another kidney problem.
Metanephric adenoma
This is a rarer benign kidney tumor that is sometimes discussed as a variant of renal adenoma. It may still cause no symptoms, but some people notice blood in the urine, side pain, or a kidney mass seen on imaging. Compared with papillary adenoma, it is more likely to come to attention because it is larger rather than because it causes dramatic symptoms.
Can I slow down the onset of symptoms?
Probably not in any proven way: there is no strong evidence that lifestyle changes or medicines can meaningfully delay symptoms from renal adenoma, which is a small, usually noncancerous growth in the kidney, and many never cause symptoms at all. Healthy habits like not smoking, keeping blood pressure in a healthy range, staying active, and managing weight may support overall kidney health, but they have not been shown to prevent this growth or reliably postpone symptoms. There are no standard preventive drugs or routine screening programs for renal adenoma, but if one has already been found, regular follow-up with your doctor can help catch changes early and guide care in a steady, sensible way.
What genetics can tell you about symptoms
For most people with renal adenoma, genetics cannot clearly predict which symptoms will happen, and many of these small kidney growths cause no symptoms at all and are found by chance on a scan. In a minority of cases, inherited genetic conditions that raise the risk of kidney tumors can make kidney growths appear earlier or alongside other kidney problems, which may affect when symptoms begin and how serious they feel. Even so, symptoms usually depend more on the tumor’s size and location than on a specific gene change.
Causes and risk factors
The exact cause of renal adenoma is often unclear. Renal adenoma is seen more often in older adults and in people with chronic kidney disease. Risk also seems higher in people on long-term dialysis and in those who develop acquired kidney cysts. Smoking and some chemical exposures may add to the risk, and researchers are still learning how these pieces fit together. Some gene changes can arise in kidney cells over time, but renal adenoma is usually not a condition passed down through families.
What are the most common causes or risk factors?
Doctors do not know one exact cause of renal adenoma, but it is more often found in older adults, people who smoke, and people living with long-term kidney disease or kidney failure, including those on dialysis. Risk also seems to be higher in men and in some people with a strong family history of kidney tumors or a rare inherited condition that makes kidney growths more likely, although these genetic causes are much less common.
Environmental and biological risk factors
Renal adenoma is a small, noncancerous growth in the kidney that is often found by chance. The main risk factors for renal adenoma are biological rather than environmental, and this condition is less studied than kidney cancer. Doctors often group risks into internal (biological) and external (environmental). For renal adenoma, age and long-term kidney damage are the clearest links, while outside exposures are not well defined.
Renal adenoma becomes more common as people get older. This likely reflects years of ongoing cell turnover and repair in kidney tissue.
Some studies have found renal adenoma more often in men than in women. Sex alone does not mean someone will develop it, but it appears to influence risk.
Renal adenoma is seen more often in people with long-standing kidney failure, especially end-stage kidney disease. For many, this means the kidney tissue has been damaged over time and replaced in part by scarred or abnormal tissue.
People on long-term dialysis can develop multiple kidney cysts, a change called acquired cystic kidney disease. This type of damaged kidney environment can make renal adenoma more likely.
Genetic risk factors
In most people, renal adenoma does not come from a clearly inherited gene change. Because these small kidney growths are often found by chance, the genetic causes of renal adenoma are still being studied, but several patterns are well known. Some risk factors are inherited through our genes. The best-described findings involve extra chromosome material and, in some families, changes in genes linked to papillary kidney tumors.
Sporadic changes: Most renal adenomas are not inherited from a parent. They usually begin after kidney cells develop DNA changes that are found only in the growth itself.
Chromosome gains: Many papillary renal adenomas have extra copies of chromosomes 7 and 17. These added copies can push kidney cells toward extra growth.
Y loss: In men, papillary renal adenoma often shows loss of the Y chromosome in tumor cells. This is a well-known genetic pattern, especially in the papillary type.
MET changes: In some families, changes in the MET gene raise the chance of papillary kidney growths, including renal adenoma. MET helps control cell growth signals, so certain variants can make growth more likely.
Family history: A strong family history of papillary kidney tumors can point to an inherited risk. This is uncommon, but it can matter when several close relatives have similar kidney growths or kidney cancer.
Lifestyle risk factors
Renal adenoma is a benign kidney tumor, and the lifestyle risk factors for renal adenoma are not as clearly established as they are for some other kidney tumors. Even so, some habits are linked to poorer kidney health and to a higher risk of renal masses in general. Lifestyle changes are not a guaranteed way to prevent renal adenoma, but they may help lower related kidney risks.
Tobacco use is the lifestyle factor most consistently linked with a higher risk of kidney tumors overall. While a direct cause-and-effect link with renal adenoma is not firmly proven, avoiding smoking may reduce harmful exposure to kidney tissue.
Overweight and obesity are associated with metabolic and hormonal changes that can affect the kidneys. These changes are more clearly tied to malignant kidney tumors, but keeping a healthy weight may also support lower overall renal tumor risk.
Physical inactivity can contribute to weight gain, insulin resistance, and poorer blood pressure control, all of which can strain the kidneys. Regular exercise may help reduce some of the broader kidney-related risks that can overlap with renal masses.
Diets high in ultra-processed foods, excess calories, and salt can worsen obesity and blood pressure, which may indirectly affect kidney health. A balanced eating pattern with vegetables, fruits, whole grains, and moderate sodium supports healthier kidney function.
Risk prevention
There is no sure way to prevent renal adenoma, and many are found by chance during scans done for something else. Prevention is about lowering risk, not eliminating it completely. Most people never notice early symptoms of renal adenoma, so the practical focus is protecting kidney health and reducing risks linked with kidney growths in general. This matters even more for people who smoke, have high blood pressure, or live with long-term kidney disease.
Smoking raises the risk of abnormal growths in the kidneys and is one of the clearest avoidable risks. Quitting can help protect kidney tissue over time, even if you have smoked for years.
High blood pressure can strain the kidneys year after year and is linked with a higher risk of kidney tumors. Keeping it in a healthy range with food choices, activity, and medicine when needed may lower that risk.
Carrying excess weight can change hormone and inflammation signals in ways that may increase kidney tumor risk. Regular movement and steady weight management can support overall kidney health as well.
Frequent use of pain relievers such as ibuprofen or naproxen, especially at high doses or for long periods, can stress the kidneys in some people. Avoiding unnecessary exposure to harmful chemicals at work and staying well hydrated can also help reduce kidney strain.
Can you prevent Renal adenoma?
There is no known, proven way to prevent a renal adenoma, which is a small noncancer growth in the kidney, because doctors do not fully understand why it forms. In general, not smoking and keeping a healthy weight may help lower the risk of some kidney problems, but this has not been clearly shown to prevent renal adenoma.
Transmission
Renal adenoma is not contagious, so it cannot be passed from one person to another through close contact, sex, blood, food, water, or the air. If you are wondering whether renal adenoma can spread from person to person, the answer is no.
For most people, renal adenoma is also not thought to follow a clear parent-to-child inheritance pattern and usually develops sporadically in kidney tissue. A doctor may ask about family history only if there are several kidney tumors or other signs that suggest a rare inherited kidney condition.
When to test your genes
Genetic testing is usually not needed for a solitary renal adenoma. It becomes more relevant if kidney tumors appear at a young age, if there are multiple or bilateral tumors, or if you have a strong family history of kidney cancer or features suggesting a hereditary tumor syndrome.
Diagnosis
Renal adenoma is often found by chance when imaging is done for something else, such as back pain, kidney stones, or a routine scan. Because these small kidney growths usually do not cause symptoms, the diagnosis of renal adenoma often starts with an unexpected finding rather than a clear warning sign. Doctors usually begin by looking closely at the size, shape, and location of the spot and deciding whether it could be another type of kidney tumor.
Ultrasound, CT scans, or MRI can show a small mass in the kidney and help estimate its size and appearance. These scans are often the first step when doctors are trying to tell a likely benign growth from a more concerning kidney tumor.
Your doctor will ask about symptoms, past kidney problems, smoking history, and any personal or family history of kidney tumors. A detailed family and health history can help put the scan findings in context, even though many people with renal adenoma feel completely well.
Blood tests check kidney function, and urine tests may look for blood or other changes that could point to a kidney problem. These results cannot confirm renal adenoma, but they help rule out other causes and guide next steps.
In some cases, a small sample of tissue is taken with a needle so it can be examined under a microscope. This can help with the diagnosis of renal adenoma, although very small kidney tumors can still be difficult to classify with complete certainty.
How is Renal adenoma diagnosed?
Renal adenoma is usually found by chance on a kidney scan, such as an ultrasound, CT scan, or MRI. The challenge is that it can look a lot like a small kidney cancer on imaging, so doctors may repeat scans over time or take a small tissue sample to check it more closely. In many cases, the diagnosis is only confirmed after the tissue is examined under a microscope, often after a biopsy or surgery, and genetic testing is not usually needed.
Stages of Renal adenoma
Renal adenoma does not have defined progression stages. This is because it is usually a small, noncancerous kidney growth that is identified by what it looks like on scans or under the microscope, rather than by a steady pattern of worsening over time. Renal adenoma is often found by chance during imaging for something else, and many people do not notice symptoms at all, although symptoms of renal adenoma can overlap with other kidney problems. Different tests may be suggested to help confirm what the growth is, such as imaging scans and sometimes review of tissue if the diagnosis is uncertain.
Outlook and prognosis
The outlook for people with renal adenoma is generally excellent, because these tumors are usually small, slow-growing, and often found incidentally. Renal adenomas are considered benign, so they do not usually affect life expectancy or cause death on their own. The main uncertainty is that some small kidney tumors can look similar on imaging or pathology, and there is ongoing debate about whether certain lesions may represent an early stage on a spectrum with low-grade renal cell carcinoma. For that reason, prognosis depends partly on how confidently the diagnosis is established and whether the mass remains stable over time. When the lesion is confirmed as a true renal adenoma and appropriately monitored or removed if needed, recurrence, spread, and mortality are expected to be extremely rare.
Long-term effects
For many people, renal adenoma does not cause major day-to-day problems and is found by chance during imaging for something else. The long-term effects of renal adenoma are often limited, especially when the growth stays small and stable over time. It’s important to remember that long-term doesn’t always mean progressive. In some cases, doctors keep watching it because a small kidney growth can be hard to distinguish from an early kidney cancer on scans alone.
Many people with renal adenoma never notice any symptoms over the long term. If the growth becomes larger or is in a sensitive area, some may develop flank discomfort or blood in the urine.
Renal adenoma may lead to repeat ultrasounds, CT scans, or MRI scans over time to check whether it is changing. This can become a long-term part of care when the diagnosis is uncertain or the mass is being monitored rather than removed.
One of the main long-term issues is that renal adenoma can look similar to some small kidney cancers on imaging. Because of this, people may need ongoing review or sometimes surgery to make the diagnosis clear.
A small renal adenoma usually does not damage kidney function on its own. If surgery is needed, long-term kidney health often remains good, though this can depend on how much kidney tissue is removed and whether other kidney disease is present.
How is it to live with Renal adenoma?
For many people, living with a renal adenoma means living with uncertainty more than with symptoms, because these small benign kidney growths are often found by chance and usually do not change day-to-day life. Some may need follow-up scans and checkups to make sure the spot stays stable, and that waiting can bring worry even when the outlook is reassuring. Around you, family members may share that anxiety or help with appointments, but in most cases this condition does not cause major limits in work, exercise, or relationships.
Treatment and drugs
Renal adenoma is usually a small, noncancerous growth in the kidney, and treatment often depends on its size, whether it is causing symptoms, and how certain doctors are about the diagnosis. Many people with renal adenoma do not need medicine to shrink it, and care may simply involve repeat imaging scans over time to watch for changes. If the growth is large, causing problems such as pain or bleeding, or looks too similar to kidney cancer on a scan, treatment for renal adenoma may involve surgery to remove part or all of the growth. Finding the right therapy can take some time, because doctors want to balance avoiding unnecessary surgery with not missing a more serious kidney tumor. If you are being monitored for renal adenoma, regular follow-up visits are important so your care team can decide whether observation is still the safest plan.
Can you cure Renal adenoma?
A renal adenoma is a small, usually noncancerous growth in the kidney, and if it needs treatment, removing it can usually take care of it completely. Many living with a renal adenoma do not need treatment at all and are simply monitored over time because these growths often stay small and cause no problems. If it grows, causes symptoms, or is hard to tell apart from kidney cancer, surgery may be recommended.
Non-drug treatment
Many living with renal adenoma feel well and only learn about it after a scan done for something else, like back pain or a kidney stone. Because these growths are usually small and often do not cause symptoms, care is often focused on watching them closely and protecting kidney function. Managing this condition often means balancing the low chance of problems against the risks of unnecessary procedures. If the mass is growing, causing symptoms, or cannot be clearly told apart from kidney cancer, treatment may be more active.
This is the most common non-drug approach for a renal adenoma that is small and not causing problems. Regular imaging, such as ultrasound, CT, or MRI scans, helps track size and shape over time. For many, treatment begins not at the pharmacy, but with careful follow-up visits and repeat scans.
Surgery may be recommended if the lump is growing, bleeding, causing pain, or looks too much like an early kidney cancer on imaging. In this procedure, the surgeon removes the mass while keeping as much healthy kidney tissue as possible. This is often the main treatment for small renal adenoma when doctors cannot be sure the growth is harmless.
Some people may be offered radiofrequency or cryoablation, which destroy the mass with heat or cold instead of removing it with surgery. This can be a good fit for older adults, people with other health problems, or those who need to spare kidney tissue. Not every approach works the same way, and ablation is usually chosen case by case.
Healthy blood pressure, good blood sugar control, not smoking, and staying well hydrated can help protect the kidneys during surveillance or after a procedure. These steps do not shrink a renal adenoma, but they can lower strain on the kidneys and support recovery. Family members often play a role in supporting new routines, especially around follow-up appointments and daily habits.
Your genes may have an impact on how drugs work for you
For people with renal adenoma, medicines are usually not the main treatment, so genetic differences do not often play a big part in day-to-day care. Most small growths are watched over time, and if treatment is needed, it is more often a procedure or surgery than long-term medicine. In some cases, a person’s genes can still affect how their body breaks down common medicines such as pain relievers or anesthesia drugs used around a procedure, but this is part of general drug response and not something specific to renal adenoma itself.
Pharmacological treatments
For most people with renal adenoma, medicines are not the main treatment because this is usually a small, benign kidney growth. Care often focuses on watching the lesion over time and treating symptoms or related problems if they come up. Medication can feel like a big step, but in renal adenoma there is usually no standard drug that shrinks or removes the growth itself. In practice, treatment for renal adenoma is often about comfort and monitoring rather than tumor-specific medicine.
There is no established medicine that specifically treats or removes a renal adenoma. Many living with renal adenoma do not need drug treatment unless they have symptoms or another kidney-related issue.
If the growth causes flank discomfort, doctors may suggest pain medicines such as acetaminophen, also called paracetamol. Nonsteroidal anti-inflammatory drugs like ibuprofen may be used cautiously in some people, but kidney function has to be considered.
Some people with a kidney mass also have high blood pressure, even if the adenoma itself is not clearly the cause. Drugs such as ACE inhibitors, angiotensin receptor blockers, calcium channel blockers, or diuretics may be used to control blood pressure and protect kidney health.
Antibiotics are not used to treat renal adenoma itself. They may be prescribed if there is a separate urinary tract infection causing symptoms like burning, fever, or cloudy urine.
Genetic influences
Because renal adenoma is often found by chance on a scan, many people are left wondering why it developed. It’s natural to ask whether family history plays a role. For most people with renal adenoma, there is no clear sign that the growth was inherited, and doctors do not usually think of it as a strongly family-linked condition. Still, gene changes can develop in kidney cells over time, and rare inherited kidney-tumor syndromes can make benign and cancerous kidney growths more likely. If renal adenoma appears at a young age, in both kidneys, or along with a family history of kidney tumors, your care team may consider genetic counseling or testing. That kind of review can help sort out whether the risk is mainly personal and random or part of a broader family pattern.
Is Renal adenoma genetic?
Genetics are not thought to play a major role in most renal adenoma cases. Unlike some kidney tumors, inherited gene changes have not been clearly linked, though research is still ongoing.
Having a genetic risk is not necessarily a diagnosis
Changes in genes, often called genetic variants, are a normal part of being human and are very common in the general population. Most of these variants do not directly affect health and are simply part of the natural differences among people. For many genes, having a variant tied to a condition suggests a possible link rather than a certain diagnosis, especially when several genes and environmental factors also play a role. In some cases, though, a single well-studied variant in a particular gene can be enough to confirm a diagnosis.
Pharmacogenetics—how genetics influence drug effects
For most people with renal adenoma, genetics do not usually point to a specific drug treatment, because these small kidney growths are often watched with scans or removed if they change in size or have features that are hard to tell apart from cancer. In everyday care, the bigger genetic question is whether the growth could be part of an inherited tendency to develop kidney tumors, especially if it shows up at a young age, if there is more than one kidney mass, or if several relatives have had similar problems. That kind of genetic testing can help doctors choose the right follow-up plan and decide whether family members may also need evaluation. Not every difference in response is genetic, but inherited differences in how the body handles medicines can sometimes affect pain relief, anesthesia, or other drugs used around a biopsy or surgery. If you are wondering how genetics affect renal adenoma treatment, it is often less about a medicine for the adenoma itself and more about confirming the diagnosis, planning monitoring, and spotting a hereditary condition when one may be present. Because renal adenoma can resemble some very early kidney cancers on imaging, doctors usually combine family history, scan results, and lab findings with any genetic information rather than relying on gene-based drug testing alone.
Interactions with other conditions
Renal adenoma is often found while doctors are checking for something else, and its main interaction with other diseases is usually through the health of the kidneys themselves. It appears more often in people living with chronic kidney disease, end-stage kidney disease, or acquired cystic kidney disease, especially after years of dialysis, so the wider kidney picture matters when it is discovered. Another important aspect is how it may link with other diseases: on scans, a renal adenoma can look similar to small kidney cancers, particularly papillary renal cell carcinoma, so doctors may need careful follow-up to tell them apart. For many, this can mean extra imaging or repeat checks rather than urgent treatment, especially if there are already other kidney problems in the background. Renal adenoma does not usually spread or directly trigger other illnesses, but if someone also has reduced kidney function, stones, cysts, or blood pressure problems, those conditions can shape symptoms and the safest treatment plan. This is one reason why early symptoms of renal adenoma, when they happen at all, are often assessed alongside other kidney and urinary conditions rather than in isolation.
How genes can cause diseases
Humans have more than 20,000 genes, each carrying out one or a few specific functions in the body. One gene instructs the body to digest lactose from milk, another tells the body how to build strong bones and another prevents the body's cells from beginning to multiply uncontrollably and developing into cancer. As all of these genes combined are the building instructions for our body, a defect in one of these genes can have severe health consequences.
Through decades of genetic research, we know the genetic code of any healthy/functional human gene. We have also identified that in certain positions on a gene, some individuals may have a different genetic letter from the one you have. We call these hotspots "Genetic Variations" or "Variants" in short. In many cases, studies have been able to show that having the genetic letter "G" in the position makes you healthy, but having the letter "A" in the same position disrupts the gene function and causes a disease. Genopedia allows you to view these variants in genes and summarizes all that we know from scientific research, which genetic letters (Genotype) have good or bad consequences on your health or on your traits.
What other conditions can cause similar symptoms to Renal adenoma?
The main condition doctors need to tell apart from a renal adenoma is kidney cancer, because a small harmless kidney growth can look similar on a scan. Kidney cysts, which are fluid-filled sacs, and other noncancer kidney masses can also be mistaken for it. If there are symptoms such as blood in the urine or pain in the side, kidney stones or a urinary tract infection may cause similar problems too.
History
Many people with renal adenoma do not notice anything day to day, and the growth is often found by chance during a scan done for something else, such as back pain or a kidney stone. That helps explain why its history is tied closely to the history of medical imaging and pathology, rather than to a long record of well-known symptoms.
Earlier doctors could only recognize small kidney growths when tissue was examined after surgery or at autopsy, so renal adenoma was mainly described by what it looked like under the microscope. Initially understood only through symptoms, later it became clearer that some of these small growths were being picked up in people who felt completely well. As medical science evolved, specialists also worked to sort out which kidney tumors were harmless, which were cancerous, and which sat in a gray area between the two.
This led to changes in how renal adenoma was classified over time. In older reports, small kidney gland-like tumors were sometimes grouped differently than they are today, and experts did not always agree on where to draw the line between a benign adenoma and a very early kidney cancer. For many living with an incidental kidney finding, this history matters because it explains why doctors may be careful with follow-up and why the wording in a pathology report can seem very specific.
More recently, better scans and more standardized pathology criteria have improved recognition of renal adenoma. Researchers later identified genetic and molecular differences between some benign kidney growths and cancers, which helped sharpen diagnosis, although classification can still depend on the exact tumor type and size. Today, the condition is generally understood as a small benign tumor of the kidney, but its history shows how kidney tumors have been redefined as knowledge has grown.