Key Points
➤ ASCO defines small renal masses (SRMs) as incidentally image-detected,
contrast-enhancing renal tumors ≤4 cm in diameter that are usually
consistent with stage T1a renal cell carcinoma.
➤ On rare occasions, SRMs may be unusual malignant tumor types such as
lymphoma, sarcoma, or a metastasis to the kidney.
➤ More than one imaging modality may be required to confirm that the lesion
is solid and/or enhancing.
➤ With more widespread use of axial imaging, usually ordered for nonspecific
gastrointestinal or musculoskeletal symptoms, there has been a continued
increase in the rate of incidentally detected SRMs.
➤ As many as 25% of SRMs are benign renal cortical tumors (eg, oncocytoma,
metanephric adenoma, and angiomyolipoma), and another 25% are indolent
in nature with limited metastatic potential (eg, chromophobe, type 1
papillary renal cancer).
• Although certain renal tumor histologies have distinct imaging characteristics, current
radiologic imaging cannot reliably discriminate benign from indolent or potentially
malignant tumors. In addition to the diagnostic dilemma, the natural history of these
lesions is variable, and many tumors demonstrate an indolent course.
Diagnosis
➤ On the basis of tumor-specific findings and competing risks of mortality, all
patients with an SRM should be considered for renal tumor biopsy when the
results may alter management (Strong Recommendation: EB-I).
➤ Active surveillance should be an initial management option for patients
who have significant comorbidities and limited life expectancy (Moderate
Recommendation: EB-I).
Qualifying statement:
▶ Absolute indication: high risk for anesthesia and intervention or life expectancy <5 years
▶ Relative indication: significant risk of end-stage renal disease if treated, SRM (<1 cm),
or life expectancy <10 years
➤ Partial nephrectomy (PN) for SRMs is the standard treatment that should be
offered to all patients in whom an intervention is indicated and who possess a
tumor amenable to this approach (Strong Recommendation: EB-I).
Treatment