MDCalc Guideline Summary: Renal Mass and Localized Renal Cancer

For patients presenting with a solid renal mass or a complex cystic lesion, clinicians should order high-resolution, multiphase, cross-sectional imaging of the abdomen to properly define the tumor's features, including complexity of the mass, contrast enhancement, and presence of fat.

Clinicians should order a CMP, CBC, and a urinalysis. Assessment for metastatic disease should include imaging of the chest.

In patients who have a solid renal mass or a Bosniak category 3 or 4 cystic renal mass, clinicians should use eGFR to determine the stage of CKD along with the level of proteinuria present.

Clinicians should counsel patients using up-to-date understanding of tumor biology along with an individualized risk assessment that accounts for sex, tumor size and complexity, histology (if available), and imaging findings. For cT1a tumors specifically, clinicians should discuss how many small renal masses carry a favorable oncologic outlook.

When counseling patients with a solid or Bosniak 3/4 complex cystic renal mass, clinicians must go over the most frequent and significant urologic and non-urologic complications associated with each treatment option, as well as how the patient's age, comorbidities or frailty, and life expectancy factor into therapeutic decisions.

Clinicians should discuss why recovery of kidney function matters when managing a renal mass, covering the risk of worsening CKD, the possibility of needing dialysis or another form of renal replacement therapy in the near or distant future, and how these factors relate to long-term survival.

Patients may benefit from nephrology referral, particularly those with elevated risk for CKD progression: this includes those with an eGFR <45 mL/min/1.73m², confirmed proteinuria, diabetic patients who already have CKD, or cases where eGFR is anticipated to drop below 30 following treatment.

Patients should be seen by genetic counselors in the following situations:

1. All patients aged 46 or younger who have renal malignancy.

2. Those with renal masses that are multifocal or bilateral.

3. Personal or family history raises concern for a hereditary renal neoplastic syndrome. 

4. A first- or second-degree relative has a history of renal malignancy or a confirmed clinical or genetic diagnosis of a familial renal neoplastic syndrome, even without a documented case of kidney cancer in that relative. 

5. The patient's pathology reveals histologic features consistent with such a syndrome.

When discussing whether a renal mass biopsy (RMB) would be useful, clinicians should counsel patients on the reasoning behind it, its positive and negative predictive values, the risks involved, and the rate at which results may be non-diagnostic.

Clinicians should think about performing an RMB when there's suspicion that a mass may be hematologic, metastatic, inflammatory, or infectious in nature.

For a solid renal mass, the decision to pursue RMB should be guided by whether the results would actually change management. RMB can be skipped for: 

1. Older or frail patients who will receive conservative management no matter what the biopsy shows.

2. Younger or healthier patients who don't wish to deal with the uncertainty it introduces.

In patients with a solid renal mass who choose to undergo RMB, the procedure should involve multiple core biopsies rather than fine needle aspiration (FNA) to optimize diagnostic yield.

For patients whose solid renal mass is under 2 cm in size, or whose mass is complex but mostly cystic, clinicians have the option of initially managing with active surveillance, allowing for intervention to be delayed if needed.

In patients with a solid or Bosniak 3/4 complex cystic renal mass, clinicians should favor AS or expectant management whenever the expected risks of treatment, or competing mortality risks, exceed the likely oncologic benefit of active intervention. For patients without symptoms, the panel advised periodic surveillance through clinical evaluation and/or imaging, guided by shared decision-making.

When the risk/benefit calculation for treating a solid or Bosniak 3/4 complex cystic renal mass is unclear and the patient leans toward AS, clinicians should consider obtaining an RMB (provided the mass is solid or has solid components) to better stratify risk. Follow-up cross-sectional imaging should be performed roughly 3-6 months afterward to check for growth. From there, ongoing surveillance can be tailored to the observed growth rate through shared decision-making, with a shift toward intervention if the mass grows substantially or if other findings indicate the risk/benefit balance no longer favors continuing AS.

When the anticipated oncologic benefit of treating a solid or Bosniak 3/4 complex cystic renal mass clearly outweighs the treatment risks and competing mortality risks, clinicians should recommend intervention. In such cases, clinicians should encourage RMB (if the mass is mostly solid) to further clarify risk. If the patient still opts for AS, clinicians should recommend close surveillance with both clinical follow-up and cross-sectional imaging, alongside periodic reassessment and ongoing counseling. 

Clinicians should consider thermal ablation (TA) as an alternative treatment approach for cT1a solid renal masses <3 cm. Among patients who choose TA, percutaneous approach is preferable to a surgical one when feasible to reduce complications.

Patients choosing TA may be offered either radiofrequency ablation (RFA) or cryoablation as treatment options.

A RMB should ideally be done before ablation, or at least at the time of the procedure, in order to establish a pathologic diagnosis and inform future surveillance.

Counseling on TA should address the higher likelihood of residual tumor or local recurrence compared with surgical removal, noting that this can often be managed with a repeat ablation if the patient opts for further treatment. 

When intervention is warranted for a cT1a renal mass, clinicians should favor partial nephrectomy (PN), as it lowers the risk of developing or worsening CKD while still delivering strong oncologic outcomes, including excellent control of the tumor locally.

Nephron-sparing techniques should be prioritized for patients with a solid or Bosniak 3/4 complex cystic renal mass who also have an anatomically or functionally solitary kidney, tumors in both kidneys, a known hereditary form of RCC, proteinuria, or known CKD.

Clinicians should also consider nephron-sparing techniques for patients with a solid or Bosniak 3/4 complex cystic renal mass who are younger, have masses in multiple locations, or have conditions likely to affect kidney function down the line, such as moderate-to-severe hypertension, diabetes, recurrent kidney stones, or severe obesity, among others.

For patients undergoing PN, clinicians should focus on preserving kidney function by maximizing the amount of healthy nephron tissue retained and minimizing prolonged warm ischemia time.

For patients undergoing PN, achieving negative surgical margins should be a priority. How much normal kidney tissue is removed should be left to the surgeon's judgment, factoring in the clinical picture and characteristics of the tumor, such as its growth pattern and how it interfaces with surrounding normal tissue. Tumor enucleation is worth considering for patients with hereditary RCC, disease in multiple locations, or severe CKD, as it helps preserve as much kidney tissue as possible.

Radical nephrectomy is the preferred approach when all of the following are present:

1. The tumor is highly complex, making PN difficult even for experienced surgeons.

2. The patient has no existing proteinuria or CKD.

3. The contralateral kidney is normal, such that the new baseline eGFR would likely stay above 45 mL/min/1.73m² even after RN.

If any of these conditions aren’t met, PN should be the preferred option unless there are significant concerns about its safety or oncologic effectiveness in that patient.

Clinicians should consider radical nephrectomy for patients with a solid or Bosniak 3/4 complex cystic renal mass when tumor size, RMB findings (if performed), and/or imaging point to greater oncologic risk.

When performing surgical excision of a renal mass, a minimally invasive technique should be considered as long as it doesn't compromise oncologic, functional, or perioperative results.

When a patient is having a renal mass surgically removed and imaging raises concern for regional lymph node involvement, clinicians should perform a lymph node dissection that removes all clinically positive nodes for staging purposes.

During surgical removal of a renal mass, clinicians should also remove the adrenal gland (adrenalectomy) if imaging or findings during surgery suggest that the tumor has spread to or directly invaded the adrenal gland.

After either PN or RN, the adjacent kidney tissue should be examined pathologically and the findings documented in order to check for underlying kidney disease; this is especially important for patients who have CKD or risk factors for CKD development.

Referral to medical oncology should be considered when there's concern for metastasis or incomplete resection.

Patients whose renal cancer was high-risk or locally advanced but fully removed should be counseled on the potential risks and benefits of adjuvant therapy and consider enrolling in adjuvant clinical trials.

Clinicians overseeing follow-up after treatment of a renal mass should talk with patients about the tumor's stage, grade, and histology, including the chances of recurrence and possible complications from treatment.

For patients whose mass proved pathologically benign, occasional clinical check-ins and lab work to monitor for treatment-related issues are appropriate, though routine imaging usually isn't necessary.

Patients treated for a malignant renal mass should have periodic follow-up consisting of a medical history, physical exam, lab work, and imaging to assess for metastasis, local recurrence, and treatment-related complications. Additional imaging targeted to specific sites can be ordered during follow-up if symptoms suggest recurrence or metastasis. Routine PET scans are not recommended, though they may be used selectively in certain cases.

For patients with treated malignant renal masses, routine lab monitoring should include serum creatinine, eGFR, and urinalysis. Additional labs, such as a CBC, LDH, LFTs, ALP, and calcium, can be ordered at clinician discretion or when concerned for advanced disease.

If a patient being followed for a treated renal mass develops worsening kidney function or proteinuria, they should be referred to nephrology.

During follow-up after treatment for malignant renal masses, a bone scan should only be ordered if the patient has at least one of the following:

1. Bone pain or other clinical symptoms. 

2. Elevated alkaline phosphatase.

3. Imaging suggestive of a bone tumor.

If findings suggest metastatic spread of renal cancer, the extent of disease should be worked up and the patient referred to medical oncology. In select patients with isolated or limited (oligo-) metastatic disease, surgical removal or ablative treatments may be considered.

If findings raise suspicion for a new primary renal tumor or local recurrence, patients should undergo metastatic workup, including imaging of the chest and abdomen. When the new primary or recurrence is confined to the same-side kidney and/or retroperitoneum, a urologist should be part of the decision-making process, and surgical removal or ablative therapy may be an option.

If a patient being followed after treatment for a malignant renal mass develops sudden neurological symptoms, they should promptly undergo MRI or CT imaging of the brain and/or spine.

For patients who underwent ablative therapy with confirmed malignancy or was non-diagnostic, pre- and post-contrast cross-sectional abdominal imaging should be obtained within 6 months (assuming no contraindications). After that, follow-up should proceed according to the IR postoperative protocol.

Clinicians should sort patients who underwent surgery (PN or RN) for a malignant renal mass into one of the following risk categories to guide follow-up: 

1. Low risk, defined as pT1 and Grade 1/2.

2. Intermediate risk, defined as pT1 and Grade 3/4 or pT2 any Grade.

3. High risk, defined as pT3 any Grade.

4. Very High Risk, defined as pT4 or pN1, macroscopic positive margin, or sarcomatoid/rhabdoid dedifferentiation.

If final microscopic surgical margins are positive for cancer, the risk category should be considered at least one level higher, and increased clinical vigilance should be exercised.

Patients who had surgery (PN or RN) for renal cancer should undergo abdominal imaging, with pre- and post-contrast CT or MRI being the preferred modalities.

Beyond the 2-year mark, alternating abdominal ultrasound with cross-sectional imaging may be an option for low-risk (LR) and intermediate-risk (IR) groups, at the physician's discretion. Past the 5-year mark, continuing abdominal imaging should be guided by shared decision-making between clinician and patient.

Patients who had surgery (PN or RN) for renal cancer should also undergo chest imaging as follows: chest X-ray (CXR) for LR and IR patients, and CT chest (preferred) for high-risk (HR) and very-high-risk (VHR) patients. After 5 years, further chest imaging should be guided by shared decision-making, and CXR may be substituted for chest CT in HR and VHR patients at that point.