Immunohistologic study on the expressions of α-fetoprotein and protein induced by vitamin K absence or antagonist II in surgically resected small hepatocellular carcinoma

Sixty-eight cases of single hepatocellular carcinoma (HCC) with less than 3 cm of diameter were immunohistochemically examined for the expressions of α-fetoprotein (AFP) and protein induced by vitamin K absence or antagonist II (PIVKA-II). In cancerous tissues, the expression rate was significantly higher for PIVKA-II (34 cases [50%]) than AFP (21 cases [31%]) (P < .05), suggesting a higher specificity of PIVKA-II to small HCC. Sixteen of the 68 cases (24%) were positive to both AFP and PIVKA-II, and in 8 of the 16 cases, AFP and PIVKA-II expressing areas within a nodule were clearly divided by a fibrous septum. According to histologic grades, PIVKA-II expression was confirmed in 2 of the 15 well-differentiated HCCs, and in the well-differentiated component of 6 of the 12 “nodule-in-nodule”–type well-differentiated HCCs. AFP expression was not found in well-differentiated HCCs, but found in 16 of the 40 moderately differentiated HCCs (40%) and in the moderately differentiated component of 3 of the 12 “nodule-in-nodule”–type well-differentiated HCCs. The positive rate in the tissues was correlated to the serum levels for both AFP and PIVKA-II. In addition, frequency of tissue–PIVKA-II expression was higher than tissue-AFP expression in the cases whose serum protein level was within the normal range. This indicates that AFP and PIVKA-II have different patterns of tissue expression and of secretion to the blood. In comparison with tissue-AFP–negative cases, tissue-AFP–positive HCCs had a larger tumor size, higher frequencies of portal vein invasion and intrahepatic metastasis, a high Ki-67 labeling index, and a lower rate of recurrence-free survival. Thus, tissue-AFP–positive HCCs are suggested to be biologically more malignant than those HCCs that are AFP-negative and PIVKA-II–positive.