Increasedabdominalimaginghasledtoanincreaseinthedetectionoftheincidentalsmallrenalmass(SRM).WithincreasingrecognitionthatthemalignantpotentialofSRMsisheterogeneous,rangingfrombenign(15%-20%)toaggressive(20%),enthusiasmformoreconservativemanagementstrategiesintheelderlyandinfirmed,suchasactivesurveillance(AS),havegrownconsiderably.AsthemanagementoftheSRMevolvestoincorporateablativetechniquesandASforlowriskdisease,theroleofrenalmassbiopsy(RMB)tohelpguideinpidualizedtherapyisevolving.Historically,theroleofRMBwaslimitedtotheevaluationofsuspectedmetastaticdisease,renalabscess,orlymphoma.However,inthecontemporaryera,theroleofbiopsyhasgrown,mostnotablytoidentifypatientswhoharborbenignlesionsandforwhomtreatment,particularlytheelderlyorfrail,maybeavoided.WhenperformingaRMBtoguideinitialclinicaldecisionmakingforsmall,localizedtumors,themostrelevantquestionsareoftenrelegatedtoproofofmalignancyanddocumentation(ifpossible)ofgrade.However,significantintratumoralheterogeneityhasbeenidentifiedinclearcellrenalcellcarcinoma(ccRCC)thatmayleadtoanunderestimationofthegeneticcomplexityofatumorwhensingle-biopsyproceduresareused.HeterogeneousgenomiclandscapesandbranchedparallelevolutionofccRCCswithspatiallyseparatedsubclonescreatesanillusionofclonaldominancewhenassessedbysinglebiopsiesandraisesimportantquestionsregardinghowtumorscanbeoptimallysampledandwhetherfutureevolutionarytumorbranchesmightbepredictableandultimatelytargetable.Thisworkraisesprofoundquestionsconcerningthegeneticlandscapeofcancerandhowtumorheterogeneitymayaffect,andpossiblyconfound,targeteddiagnosticandtherapeuticinterventions.Inthisreview,wediscussthecurrentroleofRMB,theimplicationsoftumorheterogeneityondiagnosticaccuracy,andhighlightpromisingfuturedirections.
