Analysis of proliferative activity in small hepatocellular carcinoma (HCC) (<2 cm) using proliferating cell nuclear antigen (PCNA) immunostaining. Comparison with DNA ploidy study

We examined the relationship between DNA ploidy study using flowcytometry and proliferative activity evaluated by PCNA labeling index in 25 small HCC nodules (< 2 cm) resected. Of 18 diploidy nodules, 15 (83%) were well differentiated type, 2 (11%) moderately differentiated type and 1 (6%) poorly differentiated type. Of 7 aneuploidy nodules, 2 (29%) were well differentiated type, 2 (29%) moderately differentiated type and 3 (42%) poorly differentiated type. The incidence of microscopic aggressive lesions such as capsule invasion, vascular invasion or intrahepatic metastasis was 17% (3/18) in diploidy nodules, and 43% (3/7) in aneuploidy nodules. PCNA labeling index was significantly lower in diploidy nodules (average 7.0%) than in aneuploidy nodules (average 27.0%) (P < 0.05). Ln small HCC, the diploidy nodules were often well differentiated and had rare microscopic aggressive lesions. The proliferative activity of the diploidy nodules was significantly lower than that of the aneuploidy nodules.