AIM:ToinvestigateFusobacteriumnucleatum（F.nucleatum）abundanceincolorectalcancer（CRC）tissuesanditsassociationwithCRCinvasivenessinChinesepatients.METHODS:Theresectedcancerandadjacentnormaltissues（10cmbeyondcancermargins）from101consecutivepatientswithCRCwerecollected.Fluorescentquantitativepolymerasechainreaction（FQ-PCR）wasappliedtodetectF.nucleatuminCRCandnormaltissues.ThedifferenceofF.nucleatumabundancebetweencancerandnormaltissuesandtherelationshipofF.nucleatumabundancewithclinicalvariableswereevaluated.Fluorescenceinsituhybridization（FISH）analysiswasperformedon22CRCtissueswiththehighestF.nucleatumabundancebyFQ-PCRtestingtoconfirmFQ-PCRresults.RESULTS:ThemedianabundanceofF.nucleatuminCRCtissues[0.242（0.178-0.276）]wassignificantlyhigherthanthatinnormalcontrols[0.050（0.023-0.067）]（P<0.001）.F.nucleatumwasover-representedin88/101（87.1%）CRCsamples.TheabundanceofF.nucleatumdeterminedby2-ΔCTwassignificantlygreaterintumorsamples[0.242（0.178,0.276）]thaninnormalcontrols[0.050（0.023,0.067）]（P<0.001）.Thefrequencyofpatientswithlymphnodemetastaseswashigherintheover-abundancegroup[52/88（59.1%）]thanintheunder-abundancegroup[0/13（0%）]（P<0.005）.NosignificantassociationofF.nucleatumwithotherclinico-pathologicalvariableswasobserved（P>0.05）.FISHanalysisalsofoundmoreF.nucleatuminCRCthaninnormaltissues(mediannumber6,25th3,75th10vs2,25th1,75th5)（P<0.01）.CONCLUSION:F.nucleatumwasenrichedinCRCtissuesandassociatedwithCRCdevelopmentandmetastasis.
