OBJECTIVE To conduct a comparative study of the effects of treatment using microwave ablation versus surgical resection on hematogenous dissemination of cancer cells, and on the level of immune cells of the peripheral blood in patients with small primary hepatocellular carcinoma (PHC, ≤5 cm).METHODS Forty patients with small PHC (maximal diameter ≤5 cm) were divided into a microwave group (19 cases) and a surgical operation group (21 cases). A real-time (RT) quantitative nested RT-PCR examination was performed for peripheral blood alpha-fetoprotein (AFP) mRNA. Studies were conducted to determine the level of CD3, CD4, CD8 and CD4/CD8 cells and for liver function at 30 min before, and 30 min,1 day and 3 days after the treatment.RESULTS Compared to the value before ablation, no obvious changes of CD3, CD4, CD8 and CD4/CD8 cells were found in patients of the microwave group within 7 days after ablation, but CD3, CD4 and CD4/CD8 cells in the operation group were lower compared to that before operatioh. The copy number of AFP mRNA in the peripheral blood samples of the patients of the 2 groups before operation was determined in 67.5% of the patients (27/40). There was an rise in the expression after treatment but no statistical difference was found in comparing the 2 groups. Follow-up of the patients was conducted for 1 to 16 months. For patients with continuous expression of peripheral blood AFP mRNA, the possibility of relapse and metastasis was increased.CONCLUSION Surgical resection or microwave ablation can cause more exfoliation of hepatoma carcinoma cells in the peripheral blood of patients with small PHC. The immune function of peripheral blood cells decreased in the patients after surgical resection, however, the immune function was better protected following microwave ablation. Microwave ablation causes minor reduction in liver function, and the treatment method presents a definite value for PHC therapy.