Small Renal Masses and Kidney Cancer: What a Kidney Tumour Found on a Scan Means

Mr Neil Haldar, Consultant Urological Surgeon
Uro-oncology and minimally invasive kidney surgery

Last updated: August 2026

Finding out that you have a tumour on your kidney can be alarming — particularly when it appears unexpectedly on a scan performed for something completely unrelated.

This is increasingly how kidney tumours are discovered.

You may have had an ultrasound or CT scan for abdominal pain, gallstones, kidney stones, back pain or another problem and felt perfectly well. Then the scan report mentions a renal lesion, renal mass or kidney tumour.

The immediate assumption is often that this means kidney cancer and that the kidney needs to be removed.

Neither is necessarily true.

Small kidney tumours require careful assessment because some are benign, many kidney cancers detected at this size progress relatively slowly, and some can be safely monitored rather than treated immediately. When treatment is needed, it is often possible to remove or treat the tumour while preserving the rest of the kidney.

The key question is therefore not simply:

“How do we remove this tumour?”

It is:

“What is this renal mass, how likely is it to cause harm, and which management option gives this particular patient the best balance between cancer control and avoiding unnecessary treatment?”

That distinction is central to modern management of the small renal mass.

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Key points

• A small renal mass usually means a solid kidney lesion measuring 4 cm or less.
• Many small renal masses are discovered incidentally on scans performed for another reason.
• Not every kidney mass is cancer. Benign tumours such as oncocytoma and angiomyolipoma can sometimes resemble kidney cancer on imaging.
• Current NICE kidney cancer guidance published in March 2026 recommends offering renal biopsy for suitable lesions measuring 4 cm or less when an adequate solid component can be sampled, and the result may help guide management.
• A kidney tumour under 2 cm does not automatically require surgery. Active surveillance is now a recognised option for appropriately selected patients.
• When treatment is required, partial nephrectomy is often preferable where it can be achieved safely, as it preserves healthy kidney tissue.
• Thermal ablation and, in selected circumstances, stereotactic ablative radiotherapy (SABR) may provide alternatives for patients in whom surgery is unsuitable.
• The correct decision depends on much more than tumour size: age, general health, kidney function, tumour position, biopsy findings, growth rate and individual preferences all matter.

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What is a small renal mass?

A small renal mass, often abbreviated to SRM, generally refers to a solid or enhancing tumour within the kidney measuring 4 cm or less at its largest diameter.

If such a tumour is confined to the kidney, it falls within the T1a category of kidney cancer staging.

However, the term renal mass is important.

It does not automatically mean cancer.

A scan shows us that a structural abnormality is present. Determining what that abnormality represents — and what to do about it — requires further assessment.

This distinction matters particularly with small tumours.

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How common is kidney cancer in the UK?

Around 14,500 people are diagnosed with kidney cancer each year in the UK, making it the sixth most common cancer nationally. Kidney cancer accounts for approximately 4% of new cancer diagnoses.

The commonest adult kidney cancer is renal cell carcinoma (RCC).

The main subtypes include:

• Clear cell RCC — approximately 70–80% of renal cell cancers
• Papillary RCC — approximately 5–10%
• Chromophobe RCC — approximately 3–5%
• A number of less common tumour types with different biological behaviours

Modern pathological classification has become considerably more sophisticated as our understanding of the genetics and molecular biology of kidney cancer has developed.

Another important category is urothelial carcinoma of the renal pelvis. Although this occurs within the kidney, biologically it behaves more like bladder cancer and is investigated and treated differently.

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Does a kidney mass always mean cancer?

No.

This is one of the most important things for patients with a newly discovered small renal mass to understand.

Benign kidney tumours include:

Oncocytoma

Renal oncocytomas are generally benign but can look extremely similar to renal cell carcinoma on CT or MRI.

Angiomyolipoma

An angiomyolipoma, or AML, contains varying amounts of blood vessels, muscle and fat. Those containing obvious fat can often be recognised on imaging, but fat-poor AMLs can be difficult to distinguish from kidney cancer.

Other benign and low-risk renal tumours also occur.

This uncertainty is one of the reasons why renal mass biopsy has assumed a much greater role in modern kidney cancer practice.

Removing a kidney tumour without knowing its histology may sometimes be entirely appropriate. But in other patients, particularly those with small lesions, establishing what the tumour actually is can prevent unnecessary treatment.

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Why are so many kidney tumours now discovered accidentally?

Most renal tumours are now identified through ultrasound, CT or MRI performed for other medical reasons rather than because the tumour itself has produced symptoms.

This is sometimes called an incidental renal mass.

It has fundamentally changed kidney cancer practice.

When kidney cancer presented primarily because a patient developed visible blood in the urine, flank pain or a palpable mass, tumours were frequently large by the time they were detected.

Modern imaging increasingly identifies tumours when they are only 1, 2 or 3 cm across.

And a 2 cm incidental renal mass presents a very different clinical problem from a large symptomatic kidney cancer.

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What symptoms can kidney cancer cause?

Small renal masses are usually asymptomatic.

When kidney cancer does cause symptoms, they can include:

• Blood in the urine (haematuria)
• Persistent pain or discomfort in the flank or side
• A palpable lump in the abdomen
• Unexplained weight loss
• Persistent fatigue
• Unexplained fever
• Anaemia or other abnormalities on blood testing

The traditional combination of haematuria, flank pain and an abdominal mass is now uncommon and tends to be associated with more advanced disease.

If you develop visible blood in your urine, it should be investigated even if it occurs only once.

You can read more in my guide to blood in the urine or about my Rapid Access Haematuria Service.

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What increases the risk of kidney cancer?

Recognised risk factors include:

• Smoking
• Being overweight or obese
• High blood pressure
• Chronic kidney disease
• Long-term dialysis
• A family history of kidney cancer
• Certain inherited cancer syndromes

Smoking remains one of the most important modifiable risk factors.

Most kidney cancers are nevertheless sporadic, meaning they occur without an identifiable inherited syndrome.

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Does kidney cancer run in families?

Occasionally.

Current European guidance estimates that hereditary kidney cancer may account for approximately 5–8% of cases, although this may underestimate the true number.

Genetic assessment deserves particular consideration where someone:

• develops renal cancer at 46 years or younger
• has tumours affecting both kidneys
• has several separate kidney tumours
• has a close relative with renal cell carcinoma
• has a relative with a known kidney-cancer-associated genetic mutation
• has tumour pathology suggestive of a hereditary condition

Inherited conditions associated with kidney tumours include:

• von Hippel–Lindau disease
• Birt–Hogg–Dubé syndrome
• hereditary leiomyomatosis and renal cell cancer
• hereditary papillary renal carcinoma
• succinate dehydrogenase-deficient RCC syndromes

Identifying an inherited syndrome can alter not only the patient’s own treatment and surveillance but potentially that of other family members.

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How is a small renal mass investigated?

Several pieces of information need to be brought together.

Ultrasound

Ultrasound is often where the abnormality is first discovered.

It is particularly useful in distinguishing a straightforward fluid-filled kidney cyst from a solid lesion.

An indeterminate or solid abnormality usually requires more detailed cross-sectional imaging.

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Contrast-enhanced CT

Contrast-enhanced CT is one of the principal investigations used to characterise renal masses.

A renal-protocol CT examines the kidney before and after contrast administration.

An important feature is enhancement — whether the solid part of the tumour takes up contrast.

Current EAU guidance considers an increase of approximately 15 Hounsfield units or more between unenhanced and enhanced CT images as evidence of enhancement within viable tumour tissue.

The CT also provides information about:

• tumour size
• tumour position
• proximity to the collecting system
• nearby blood vessels
• the renal vein
• the opposite kidney
• surrounding tissues
• lymph nodes
• evidence of more advanced disease

This information becomes important when deciding whether partial nephrectomy is technically feasible.

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Do I always need a CT scan of my chest?

Not necessarily.

Chest imaging is important when staging kidney cancer because the lungs are one of the common sites to which renal cancer may spread.

However, the likelihood of metastatic disease from a very small incidental T1a tumour in an otherwise well patient is extremely low.

Imaging therefore needs to be proportionate to the patient’s individual situation rather than applied mechanically.

Bone scans, brain scans and PET-CT are also not routinely required for otherwise localised kidney cancer unless symptoms or other findings provide a specific reason for them. Current EAU guidance advises against routine bone scanning or FDG-PET/CT for primary RCC staging.

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What is the Bosniak classification?

Not every kidney lesion is solid.

Kidney cysts are extremely common, and most simple cysts are harmless.

More complex cystic lesions are assessed using the Bosniak classification.

Broadly:

• Bosniak I — simple benign cyst
• Bosniak II — benign or essentially benign cystic lesion
• Bosniak IIF — requires imaging follow-up
• Bosniak III — indeterminate lesion with a significant possibility of malignancy
• Bosniak IV — contains features strongly suggestive of malignancy

Management depends on the cyst’s size, its solid component, imaging characteristics and the patient’s circumstances.

Importantly, modern management does not mean that every Bosniak III or small Bosniak IV lesion automatically proceeds directly to surgery.

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What is a RENAL or PADUA score?

When planning partial nephrectomy, tumour size alone does not tell the whole story.

A 3 cm tumour sitting prominently on the outside surface of the kidney may be considerably easier to remove while preserving the kidney than a 2.5 cm tumour buried deep beside major vessels and the urine drainage system.

Scoring systems such as RENAL and PADUA describe this anatomical complexity.

They assess features including:

• tumour size
• how much lies within versus outside the kidney
• proximity to the collecting system
• location within the kidney
• relationship to important structures

They do not tell us whether a tumour is malignant.

Instead, they help us understand how technically demanding kidney-preserving surgery may be.

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Do small kidney tumours need a biopsy?

This is one area where UK kidney cancer practice is changing significantly.

The first dedicated NICE guideline on kidney cancer — NG256, published in March 2026 — recommends offering renal biopsy to adults with a suitable renal lesion measuring 4 cm or less when there is enough solid tissue to obtain a meaningful sample.

A biopsy may be especially valuable when its result could alter the choice between:

• active surveillance
• surgery
• thermal ablation
• another form of treatment

It is also important before ablative treatment because ablation destroys the tumour without producing the same complete surgical specimen obtained during partial nephrectomy.

Biopsy may be unnecessary when it would not change management, or when obtaining a safe and adequate sample is technically inappropriate.

European EAU guidance is slightly more selective, recommending biopsy particularly before ablation and in selected patients considering active surveillance.

The important principle is therefore not:

“Every kidney tumour must be biopsied.”

It is:

“Would knowing the histology materially improve this patient’s treatment decision?”

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Is kidney tumour biopsy safe?

Modern renal mass biopsy is generally a safe image-guided procedure.

It is usually performed using a core biopsy needle, often under CT or ultrasound guidance.

Patients understandably sometimes worry that putting a needle into a cancer may spread it.

This concern originates from much older experience. With modern coaxial biopsy techniques, clinically significant tumour seeding is regarded as exceptionally uncommon.

The more common limitation is simply that a biopsy may occasionally fail to obtain enough representative tissue to make a definite diagnosis, in which case repeat biopsy may be considered.

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What happens if my kidney tumour is less than 2 cm?

This is an especially important question following the publication of the new NICE guideline.

For localised solid renal masses under 2 cm, NICE recommends that active surveillance should be considered after appropriate imaging, staging and multidisciplinary discussion. If the patient does not wish to continue surveillance, surgery or thermal ablation can then be considered.

That is a significant conceptual shift.

It recognises that treating every tiny incidental renal mass immediately may expose some patients to procedure-related risks for a tumour that might never have caused harm.

This does not mean a 1.8 cm tumour can simply be ignored.

It means considering its biology, imaging characteristics, biopsy findings where appropriate, growth, and the patient’s wider health before intervention.

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What are the treatment options for a small renal mass?

There are four principal strategies:

1. Active surveillance
2. Partial nephrectomy
3. Thermal ablation
4. Radical nephrectomy

SABR has also emerged as an option for selected patients who are not suitable for surgery or conventional ablation.

Tumour size alone does not determine the best treatment.

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1. Active surveillance

Active surveillance means deliberately monitoring a kidney tumour rather than treating it immediately.

It is not the same as doing nothing.

Patients remain in a structured programme of imaging and clinical review so treatment remains available if the tumour later shows concerning behaviour.

Studies of small renal masses managed in this way show that metastatic progression is uncommon. A systematic review cited by the EAU found metastatic disease in approximately 1.8% of patients with small renal masses undergoing surveillance, although patients selected for surveillance are not identical to those selected for immediate surgery.

The prospective DISSRM programme has also demonstrated very slow median growth among many lesions selected for surveillance.

Who might be suitable?

Active surveillance may be particularly attractive when:

• the tumour is very small, particularly under 2 cm
• the patient is older
• there are important competing health problems
• surgery carries substantial risk
• kidney function is already impaired
• there is a solitary kidney
• imaging or biopsy suggests an indolent tumour
• the patient wishes to defer treatment following an informed discussion

It can also be entirely reasonable in selected younger and fitter patients when the tumour and circumstances support that decision.

The decision should be individual, not based on age alone.

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What does active surveillance actually involve?

Current NICE guidance suggests imaging:

• 3–6 months after starting surveillance
• again at approximately 12 months
• at least annually during years 2–5

CT, MRI, or ultrasound may be used depending on the characteristics of the tumour and the patient. Alternating imaging techniques can sometimes reduce cumulative radiation exposure.

NICE recommends discussing intervention if, among other factors:

• the tumour grows by more than 5 mm in a year
• it is likely to exceed 4 cm before the next scan
• there is evidence of stage progression
• the patient’s circumstances change
• the patient decides they would prefer treatment

This provides a much clearer framework than the sometimes misleading idea of simply “watching and waiting.”

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2. Partial nephrectomy — removing the tumour while preserving the kidney

When surgery is appropriate for a small localised kidney tumour, the objective is often to remove the tumour while retaining as much healthy kidney as possible.

This operation is called a partial nephrectomy or nephron-sparing surgery.

Instead of removing the whole kidney, the surgeon removes the tumour with an appropriate margin and reconstructs the remaining kidney.

This is particularly important for patients with:

• reduced kidney function
• only one functioning kidney
• tumours in both kidneys
• conditions that increase their future risk of chronic kidney disease

But kidney preservation is desirable more widely whenever it can be achieved safely without compromising cancer treatment.

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Open, laparoscopic or robotic partial nephrectomy?

Partial nephrectomy can be performed:

• through open surgery
• laparoscopically
• using robotic-assisted laparoscopic surgery

Current EAU evidence indicates that partial nephrectomy can be performed appropriately by any of these approaches, depending on tumour complexity and surgeon expertise.

Robotic assistance has become widely used for partial nephrectomy because the magnified view and articulated instruments can facilitate tumour excision and kidney reconstruction, particularly in complex cases.

However, the technology itself is not the treatment objective.

The important questions are:

• Can the cancer be adequately treated?
• Can useful kidney tissue be preserved?
• What is the complexity of this particular tumour?
• Which approach can be performed most safely by an appropriately experienced surgeon?

I have performed more than 600 laparoscopic kidney operations during my career. When a patient’s tumour would be better treated with a technique outside my practice, I refer to a colleague with the appropriate specialist expertise rather than letting the availability of a particular technique determine treatment.

You can read more about my approach to kidney cancer treatment and kidney surgery.

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What is warm ischaemia?

During some partial nephrectomy operations, blood flow to the kidney is temporarily reduced by clamping the renal artery while the tumour is removed and the kidney reconstructed.

This is called warm ischaemia.

Historically, considerable attention was given to achieving a particular maximum number of minutes of clamping.

Modern thinking is more nuanced.

The overall aim is to:

• preserve as much healthy functioning kidney as possible
• avoid unnecessary interruption of blood flow
• perform a precise cancer operation
• reconstruct the kidney safely

Off-clamp or selective-clamping techniques can be useful in certain situations, particularly where renal function is already compromised, but they are not automatically superior for every patient. Current EAU evidence shows similar functional outcomes between off-clamp and on-clamp approaches in appropriately selected patients with two normally functioning kidneys.

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What are the risks of partial nephrectomy?

Recognised risks include:

• bleeding
• infection
• urine leakage if the collecting system is entered
• reduced kidney function
• the need for radiological embolisation to control delayed bleeding
• conversion to radical nephrectomy if kidney preservation proves unsafe or technically impossible
• general risks associated with major surgery and anaesthesia

The complexity of the individual renal tumour strongly influences these risks.

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3. Thermal ablation

Thermal ablation destroys a renal tumour without surgically removing it.

The principal techniques include:

Cryoablation

The tumour is frozen to destroy the cancer cells.

Radiofrequency ablation

Radiofrequency energy generates heat that destroys the tumour.

Microwave ablation

Microwave energy heats and destroys tumour tissue.

These procedures are often performed through needles placed through the skin under image guidance.

They may be particularly attractive for:

• small tumours
• patients at increased surgical risk
• people with significant medical conditions
• selected patients with reduced kidney function
• patients with a solitary kidney
• those who wish to avoid surgery where oncologically appropriate

Tumour position matters considerably. A small tumour projecting away from the kidney and located safely away from the bowel, ureter and other vulnerable structures may be far more suitable for percutaneous ablation than an anatomically central lesion.

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Is ablation as good as surgery?

The comparison is not straightforward because patients undergoing ablation are frequently older or less medically fit than those undergoing surgery.

Ablation can provide excellent cancer control in appropriately selected small tumours.

However, available comparative evidence suggests a greater risk of local tumour persistence or recurrence than after partial nephrectomy, and the EAU emphasises that the evidence comparing these approaches has limitations.

One advantage is that ablation can often be repeated if a residual or recurrent focus is subsequently detected.

A renal biopsy should generally be obtained before ablative treatment so that the tumour’s histology is known.

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4. Radical nephrectomy — removing the whole kidney

A radical nephrectomy removes the entire affected kidney.

This remains an extremely important and appropriate cancer operation.

The question is not whether radical nephrectomy is a good operation.

It is whether removing the whole kidney is necessary for this particular tumour.

Radical nephrectomy may be preferable where:

• the tumour is large
• it is highly central or anatomically complex
• safe partial nephrectomy is unlikely to be possible
• there is extensive involvement of important structures
• kidney preservation would introduce disproportionate surgical risk
• preserving the affected kidney would provide little useful functional benefit

For a straightforward small peripheral renal mass, by contrast, a recommendation to remove an otherwise functioning entire kidney deserves a clear explanation.

A second opinion is entirely reasonable if you have been advised to undergo radical nephrectomy for a relatively small tumour and you would like to understand whether kidney-preserving treatment is feasible.

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What is SABR for kidney cancer?

Stereotactic ablative body radiotherapy, usually abbreviated to SABR or SBRT, delivers highly focused radiotherapy to the tumour.

Its role in primary kidney cancer has developed rapidly.

NICE now includes SABR as an option in selected patients with localised renal tumours who cannot undergo surgery, particularly where thermal ablation is unsuitable and active surveillance is not appropriate or has been declined.

It is not currently the usual first treatment for a fit patient with an operable small renal tumour, but it represents an important additional option for patients who previously might have had very limited choices.

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How do you decide between surveillance, biopsy, ablation and surgery?

This is where specialist assessment matters most.

There is rarely a single number on a scan that determines the answer.

I consider:

The tumour

• size
• location
• whether it is solid or cystic
• degree of enhancement
• rate of growth
• anatomical complexity
• biopsy histology where available
• evidence of local extension

The kidneys

• overall kidney function
• function and appearance of the opposite kidney
• whether there is a solitary kidney
• pre-existing chronic kidney disease
• previous kidney surgery

The patient

• age
• general health and frailty
• cardiovascular risk
• other medical conditions
• life expectancy
• personal priorities and concerns

The available treatments

• probability of cancer control
• technical feasibility of partial nephrectomy
• surgical risks
• suitability for ablation
• consequences of losing an entire kidney
• potential future treatments if the tumour changes

The correct treatment for a fit 50-year-old with a 3.8 cm suspicious renal tumour may therefore be quite different from the correct treatment for an 82-year-old with significant heart disease and a 1.5 cm tumour that has not changed in size.

That is not an inconsistency.

It is personalised medicine.

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What happens with kidney tumours larger than 4 cm?

Once a renal tumour exceeds 4 cm, it no longer falls within the small renal mass/T1a category.

Broadly:

• T1a — 4 cm or smaller, confined to the kidney
• T1b — over 4 cm and up to 7 cm, confined to the kidney
• T2 — over 7 cm and confined to the kidney
• T3 — extension into major veins or surrounding tissues without extension beyond Gerota’s fascia
• T4 — invasion beyond Gerota’s fascia, including contiguous extension into the ipsilateral adrenal gland

Partial nephrectomy can sometimes still be performed for tumours larger than 4 cm.

Size alone does not determine whether the kidney must be removed.

The tumour’s anatomy and the patient’s circumstances are crucial.

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What if kidney cancer has spread?

Treatment for metastatic kidney cancer has changed enormously.

For many years, treatment relied principally on targeted drugs.

Modern systemic therapy frequently uses combinations involving immune checkpoint inhibitors and targeted therapies.

Current EAU first-line options for metastatic clear-cell RCC include combinations such as:

• nivolumab plus ipilimumab
• pembrolizumab plus axitinib
• pembrolizumab plus lenvatinib
• nivolumab plus cabozantinib

Choice depends on tumour subtype, prognostic group, previous treatment and the patient’s individual circumstances.

Surgery also remains an option for carefully selected patients.

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Is treatment needed after kidney cancer surgery?

Most people with small, low-risk localised kidney cancers do not require drug treatment after surgery.

For selected patients with clear-cell renal cell carcinoma at increased risk of recurrence, adjuvant pembrolizumab may be considered following nephrectomy.

NICE includes pembrolizumab as an option for appropriate higher-risk patients after surgery.

This decision is normally made through specialist multidisciplinary assessment.

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What is the outlook for kidney cancer?

Prognosis depends strongly on the stage and biological characteristics of the cancer.

Cancer Research UK reports that among people diagnosed in England between 2016 and 2020, approximately:

• 90% with Stage I kidney cancer survived their cancer for at least five years
• 75% with Stage II
• 75% with Stage III
• 15% with Stage IV

These are population statistics and cannot predict what will happen to an individual patient. Outcomes also continue to evolve as treatment improves.

For someone with a very small localised renal mass, the starting position is therefore often much more favourable than the word “cancer” initially suggests.

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Will I need dialysis after kidney surgery?

Usually not.

Partial nephrectomy is specifically intended to preserve functioning renal tissue.

Even after removal of an entire kidney, most people with a healthy opposite kidney do not require dialysis.

The risk becomes more important if there is:

• significant chronic kidney disease before surgery
• poor function in the opposite kidney
• a solitary kidney
• diabetes or severe hypertension
• bilateral kidney disease

Kidney function therefore forms part of treatment planning from the beginning rather than being considered only after surgery.

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Can you live normally with one kidney?

In most cases, yes.

A healthy remaining kidney can compensate significantly following removal of the other kidney.

Long-term measures generally include:

• maintaining good blood-pressure control
• maintaining a healthy weight
• avoiding smoking
• keeping adequately hydrated
• avoiding unnecessary long-term use of medicines that can damage kidney function, particularly certain anti-inflammatory drugs
• periodic monitoring of kidney function and blood pressure

Individual advice may differ if kidney function was already impaired before surgery.

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Frequently asked questions

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Getting a second opinion about a kidney tumour

A diagnosis of a renal mass often comes completely unexpectedly.

It is therefore understandable for patients to feel pressure to “get it out” as quickly as possible.

Sometimes that is exactly the right decision.

Sometimes it is not.

With a small renal mass, there may be time to establish the diagnosis more clearly, understand the tumour’s anatomy and biology, consider whether treatment is necessary now, and determine whether the kidney can be preserved if treatment is required.

If you have been told that you have a kidney tumour, renal mass or suspected kidney cancer, I can review your imaging and discuss the options with you.

This may include:

• renal mass biopsy
• active surveillance
• partial nephrectomy
• laparoscopic kidney surgery
• radical nephrectomy
• thermal ablation
• referral for robotic surgery or other specialist treatment where this is the better option

I also regularly see patients seeking a second opinion before kidney surgery, particularly when complete removal of the kidney has been proposed for a relatively small tumour.

Book a private consultation

You can also read more about:

• Kidney cancer diagnosis and treatment
• Blood in the urine
• Rapid Access Haematuria Service
• Clinic locations
• Fees and private medical insurance

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About Mr Neil Haldar

Mr Neil Haldar MBBS MD FRCS (Eng) FRCS (Urol) is a Consultant Urological Surgeon with more than 20 years’ experience in urology and a specialist interest in uro-oncology and minimally invasive surgery.

He has performed more than 600 laparoscopic kidney operations and sees patients with newly diagnosed renal masses and kidney cancer, including those seeking specialist second opinions.

Private consultations are available across Buckinghamshire, Berkshire, West Hertfordshire, North West London and the Thames Valley.

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Key sources

• NICE NG256 — Kidney cancer: diagnosis and management, published 19 March 2026
• European Association of Urology Guidelines on Renal Cell Carcinoma
• Cancer Research UK — Kidney cancer incidence and survival statistics
• DISSRM — Delayed Intervention and Surveillance for Small Renal Masses
• Bosniak Classification of Cystic Renal Masses, Version 2019

This article provides general medical information and does not replace assessment or advice from your own doctor. If a renal mass has been identified on a scan, it should be reviewed by an appropriately experienced clinician. Visible blood in the urine should always be investigated.