Objective: To study the micrometastasis distribution in liver tissue surrounding hepatocellular carcinoma (HCC), and provide reference for appropriate surgical safety margin.
Methods: Thirty-six patients with HCC but without clinical metastasis underwent hepatectomy. Their specimens showing ample surgical margin were made into giant sections. Tumor micrometastasis in liver tissue around the primary tumor were examined microscopically. In each specimen, the surrounding tissue was divided into proximal(p) and distal(d) areas. In either area, three lines of demarcation 0.5 cm, 1.0 cm, and 2.0 cm away from the margin of the primary tumor were designated as L(0.5), L(1.0) and L(2.0). Therefore, the surrounding tissue was divided into six zones - Z(p0.5), Z(p1.0), Z(p2.0) and Z(d0.5), Z(d1.0), Z(d2.0). The maximum micrometastasis spread distance (MMSD) and density (D(p0.5), D(p1.0), D(p2.0) and D(d0.5), D(d1.0), D(d2.0)) in each zone were analyzed after search for micrometastasis in the giant sections.
Results: 72.5% (111/153) micrometastases were found in form of microscopic tumor emboli. Their spread distance could be up to 6.1 cm. In 66.7% (24/36) specimens, micrometastases were found in the surrounding tissue. In 91.7% (22/24) of them, the distal MMSD was less than 3 cm. The proximal MMSD was less than 1.5 cm in 92.3% (12/13). The comparison of micrometastasis density in the different zones were D(d0.5) > D(d1.0) > D(d 2.0); D(p0.5) > D(p1.0) > D(p2.0); D(d1.0) > D(p1.0); D(d2.0) > D(p2.0) with significant differences.
Conclusion: (1) Micrometastases of HCC exist mainly in form of microscopic tumor emboli, (2) The longer the distance from the primary focus, the lower the micrometastasis incidence, (3) In zones more than 0.5 cm away from the primary focus, tumor micrometastasis incidence is significantly lower in the proximal zones than that in the distal zones and (4) For HCC patients without clinical metastasis, a surgical margin of 3 cm wide in the distal area and 1.5 cm wide in the proximal area may reduce the rate of postoperative recurrence.