Patient education › Kidney cancer
Kidney cancer
Most kidney tumours today are found by accident, on a scan ordered for something else entirely. That changes the conversation, because many are small, some are not cancer at all, and not every one needs to come out immediately.
Walk in prepared
Kidney masses are often found unexpectedly, which means you may be meeting a urologist with no warning and no time to prepare.
Dr. Weiner uses WellPrept to help patients gather their records and write down their questions ahead of time. It is free, takes about ten minutes, and you do not need to be his patient to use it. If you are seeing another urologist, or preparing for a second opinion anywhere, it works just as well.
Organize your records and questions before you sit down. Free, and yours to keep whichever doctor you see.
Found while looking for something else
More than half of kidney masses are discovered incidentally during imaging done for unrelated reasons. The classic textbook presentation of blood in the urine, flank pain and a lump you can feel is now uncommon. Because of this, the typical kidney tumour today is small and confined, and outcomes for localized disease are good.
Not everything on a scan is cancer
This is the single most useful thing to understand. A meaningful proportion of small kidney masses removed at surgery turn out to be benign, and the smaller the mass, the likelier that is. Under a centimetre, benign findings are common; above seven centimetres they are rare. Some benign tumours, such as angiomyolipomas, can often be recognized on imaging because they contain fat.
The practical consequence: for a small mass, "we found something on your kidney" is not the same sentence as "you have cancer," and it is fair to ask which one your doctor means.
When a biopsy is worth doing
A kidney biopsy is not automatic, because for many people the result would not change what happens next. It earns its place when it would: when lymphoma, infection or a spread from another cancer is possible, when kidney function is poor enough that surgery is a serious risk, when the choice is between removing part or all of the kidney, and always before or during ablation, since ablation destroys the tissue that would otherwise be examined.
It is worth knowing the limits. A biopsy that shows cancer is highly reliable. A biopsy that shows no cancer is much less so, because the needle may simply have missed. Around one in seven biopsies come back uninformative, and grade is not always accurate on a needle sample. Serious complications are uncommon.
Four reasonable paths
For a small, localized mass, more than one answer can be correct. Which fits depends on the tumour, your kidneys, your other health and your priorities.
Active surveillance
Reasonable initial management for solid masses under about two centimetres, and for masses that are mostly cystic. It is prioritized when the risks of a procedure or competing health problems outweigh what treatment would gain. Monitoring means repeat imaging within a few months to establish how fast it is growing, then at individualized intervals. Growth beyond about three centimetres, growth faster than roughly half a centimetre a year, or a worrying change in appearance are the usual reasons to act.
Partial nephrectomy
Removing the tumour and leaving the rest of the kidney. Prioritized for tumours up to four centimetres, and strongly favoured for anyone with a solitary kidney, tumours on both sides, an inherited syndrome, existing kidney disease or protein in the urine. It preserves substantially more kidney function than taking the whole kidney, at the cost of a somewhat higher rate of urinary complications.
Radical nephrectomy
Removing the whole kidney. Appropriate when the tumour is complex enough that removing only part of it would be difficult even in expert hands, and when your other kidney is healthy and your function is expected to stay reasonable afterwards. It is a good operation in the right situation, and the wrong one when kidney tissue could have been saved.
Thermal ablation
Freezing or heating the tumour, usually through the skin rather than through an incision. An option for solid masses under about three centimetres. Recurrence after a single treatment is somewhat higher than after surgery, but repeat ablation largely closes that gap, and recovery is easier. Effectiveness falls off above three centimetres.
Things that get missed
Genetics, if you are young or have more than one tumour
Inherited syndromes account for a small but real share of kidney cancers, and they tend to appear decades earlier than sporadic disease. Genetic counselling is recommended if you are 46 or younger, if you have tumours in both kidneys or several in one, if your pathology suggests a syndrome, or if there is kidney cancer in the family. It matters for your relatives as much as for you.
Protecting the kidney you keep
After treatment, the things that slow kidney disease are unglamorous and effective: controlling blood pressure and diabetes, stopping smoking, avoiding substantial weight gain, and being careful with anti-inflammatory painkillers and unnecessary contrast scans. Ask whether you should see a nephrologist, particularly if your kidney function is already reduced or you have protein in your urine.
Follow-up runs longer than people expect
How closely you are followed depends on the pathology, running from roughly six months out to several years, with imaging of the abdomen and chest and periodic blood tests. Higher-risk pathology is watched more closely and starts sooner. It is worth knowing that a meaningful minority of recurrences appear more than five years later, which is why surveillance is not always over at the five-year mark.
Risk factors you can act on
Smoking and obesity together account for a substantial share of kidney cancer, and high blood pressure contributes as well. None of this is a reason for self-blame after a diagnosis, but all of it is worth addressing afterwards, because it affects your kidneys and your heart regardless of the cancer.
Worth asking out loud
With a small kidney mass you usually have time. Use it to ask properly.
About the mass
- How large is it, and how complex?
- What is the chance it is benign?
- Would a biopsy change what you recommend?
- Has it been imaged with contrast, before and after?
About the options
- Is active surveillance reasonable for me?
- Can you remove the tumour and leave the kidney?
- If not, why not, specifically?
- Am I a candidate for ablation instead?
About my kidneys
- What is my kidney function now?
- What would it likely be after each option?
- Do I have protein in my urine?
- Should I see a nephrologist?
About afterwards
- What does follow-up look like, and for how long?
- Should I have genetic counselling?
- What can I do to protect the kidney I keep?
- What would make you want to see me sooner?
Sources and further reading
This page was written for patients and reviewed by Dr. Weiner. It reflects current professional guidelines, which are written for clinicians. The patient-facing versions below are free and often easier to read.
- Renal Mass and Localized Renal Cancer: AUA Guideline, American Urological Association.
- Kidney cancer, Urology Care Foundation.
- Urology Care Foundation, the AUA's patient education arm.
- NCCN Guidelines for Patients, free plain-language versions of the treatment guidelines.
This is general education, not medical advice. It cannot account for your imaging, your pathology, your other health conditions or what matters to you. Take it to your own doctor and work through it together. If anything here conflicts with what your urologist has told you, raise it with them directly rather than assuming either of us is wrong.
Last reviewed September 2026 by Adam B. Weiner, MD.