AIM:To assess the rate and risk factors for tumour seeding in a large cohort of patients.METHODS:Over an 8-year period,1436 hepatocellular carcinoma(HCC) patients with 2423 tumour nodules underwent 3015 image-guided percutaneous cryoablation sessions [1215 guided by ultrasonography and 221 by spiral computed tomography(CT)].Follow-up CT or magnetic resonance imaging was performed every 3 mo.The detailed clinical data were recorded to analyse the risk factors for seeding.RESULTS:The median follow-up time was 18(range 1-90) mo.Seeding was detected in 11 patients(0.76%) at 1-24(median 6.0) mo after cryoablation.Seeding occurred along the needle tract in 10 patients and at a distant location in 1 patient.Seeded tumours usually showed similar imaging and histopathological features to the primary HCCs.Univariate analyses identified subcapsular tumour location and direct subcapsular needle insertion as risk factors for seeding.Multivariate analysis showed that only direct subcapsular needle insertion was an independent risk factor for seeding(P = 0.017;odds ratio 2.57;95%CI:1.47-3.65).Seeding after cryoablation occurred earlier in patients with poorly differentiated HCC than those with well or moderately differentiated HCC [1.33 ± 0.577 mo vs 11.12 ± 6.896 mo;P = 0.042;95%CI:(-19.115)-(-0.468)].CONCLUSION:The risk of seeding after cryoablation for HCC is small.Direct puncture of subcapsular tumours should be avoided to minimise seeding. AIM: To assess the rate and risk factors for tumor seeding in a large cohort of patients. METHODS: Over an 8-year period, 1436 hepatocellular carcinoma (HCC) patients with 2423 tumor nodules underwent 3015 image-guided percutaneous cryoablation sessions [1215 guided by ultrasonography and 221 by spiral computed tomography (CT)]. Follow-up CT or magnetic resonance imaging was performed every 3 mo. The detailed clinical data were recorded to analyze the risk factors for seeding. RESULTS: The median follow-up time was 18 (range 1-90) mo. Seeding was detected in 11 patients (0.76%) at 1-24 (median 6.0) mo after cryoablation. Seeding occurred along the needle tract in 10 patients and at a distant location in 1 patient. Seeded tumors usually showed similar imaging and histopathological features to the primary HCCs.Univariate analyzes identified subcapsular location and direct subcapsular needle insertion as risk factors for seeding. Multivariate analysis showed that only direct subcapsular needle i nsertion was an independent risk factor for seeding (P = 0.017; odds ratio 2.57; 95% CI: 1.47-3.65). Seeding after cryoablation occurred earlier in patients with poorly differentiated HCC than those with well or moderately differentiated HCC [1.33 ± 0.577 mo CONCLUSION: The risk of seeding after cryoablation for HCC is small. Direct puncture of subcapsular tumors should be avoided to minimize seeding.