Portal vein invasion and intrahepatic micrometastasis in small hepatocellular carcinoma by gross type

Background/ aims: Recurrence due to clinically undetectable intrahepatic metastasis and portal vein invasion of HCC cells is not ‘uncommon’ even in small HCCs. The present study investigated the relationship between these factors and macroscopic types of HCC. Methods: Surgically resected 209 cases of small HCC less than 3 cm in diameter were examined. Macroscopically, 209 cases were divided into ‘vaguely nodular type’, ‘single nodular type’, ‘single nodular type with extranodular growth’ and ‘confluent multinodular type’. Results: None of the vaguely nodular type had intrahepatic metastasis or portal vein invasion, and their diameter was significantly smaller than the other three types. ‘Single nodular type with extranodular growth’ and ‘confluent multinodular type’ show higher frequency of portal vein invasion and intrahepatic metastases than ‘single nodular type’. Among 149 metastatic lesions, the distance was 10 mm or shorter in 118 (79.2%). Conclusions: It is important to precisely determine the gross type of small HCC by diagnostic imaging in order to predict portal vein invasion and micrometastasis. It is also important to ablate the tumor with enough surrounding tissue 1 cm in width at least to prevent the recurrence from those micrometastasis.