Resection remains the gold standard in the treatment of liver tumors. But radiofrequency ablation allows destruction of small liver tumors. The aim of this study was to evaluate the effect of surface application of a saline-linked dissecting sealer (TL) on the tumor bed that might contain residual microscopic tumor cells after resection (in situ margin).Five hepatitis-infected woodchucks bearing primary liver tumors were used. Tumors > 1 cm in diameter were removed by tumorectomy. Alternately, the in situ margins were treated or not by TL. All samples were frozen and stained with hematoxylin and eosin and nicotine adenine dinucleotide (cell viability test). The median tumor diameter was 22 mm (range 10 to 53 mm). Among 84 in situ retrieved samples, 50 were from TL-treated tumors and 34 were from untreated controls.The mean (+/-SD) heat-zone area was 12.6+/-2.8 mm in TL-treated tumors and 0.6+/-0.7 mm in controls (p < 0.001). Hematoxylin and eosin and nicotine adenine dinucleotide analyses showed 70% to 98% of cell destruction inside the heat-zone area in the TL-treated samples. There were macroscopic residual tumor cells (R2 resection) in 53 samples, with a median length of tumoral tissue inside the in situ margin of 3.5 mm. Among them, the heat-zone area was considerably longer in TL-treated versus untreated controls (13.3+/-2.6 mm versus 0.7+/-0.9 mm, p < 0.001). In samples with no residual tumor cells or microscopic residual tumor cells (R0/R1; n=31), the length of the tumoral margin was similar between TL-treated and untreated controls (0.7+/-0.2 mm and 0.9+/-0.2 mm, respectively, p=NS). Compared with controls, no viable cell was visible (up to 5 mm of depth) in the in situ margins in the TL-treated samples (p < 0.05).These results support the hypothesis that surface application of the TL device on the in situ margins after tumorectomy could induce a substantial heat-zone area ranging from 10 to 13 mm, inside which, on a regressive heat gradient, up to 98% of cells could be destroyed. These observations could help to reduce marginal recurrence, especially in patients requiring multiple tumorectomies or complex liver resections for malignancy.