Pathology of small hepatocellular carcinoma. A proposal for a new gross classification.

Review of 61 surgically resected small hepatocellular carcinomas (HCC) less than or equal to 3 cm in diameter yielded a simple gross classification system of five types based on tumor shape, which is highly correlated with microscopic and clinical features, including prognosis. Type 1 (single nodular type) tumors (n = 13) are expansile, roughly spheric, and often encapsulated. In Type 2 tumors (single nodular type with extranodular growth) (n = 21), replacing growth is often seen in the area of extranodular growth. Type 3 tumors (contiguous multinodular type) (n = 19) consist of small nodules growing in contiguity, often with replacing growth at the periphery. Type 4 (poorly demarcated nodular type) is a rare tumor showing infiltrating growth at its border. The authors define early HCC (n = 5) as the presence of tumor without destruction of the underlying liver structure. The lesions experienced are tiny (less than or equal to 1.2 cm) and well differentiated. Poorly differentiated histologic characteristics and elevated alpha fetoprotein are more common in Types 2 and 3 than in Type 1. Type 1 has the highest rates of positive serum hepatitis B surface antigen and liver cirrhosis; portal vein tumor thrombus (PT) and/or intrahepatic metastasis (IM) is rare (7.7%), and the effect of transcatheter arterial embolization (TAE) is remarkable. This contrasts with Type 2, which has a high rate of PT and/or IM (71.4%) and multiple local recurrences (40%), and with Type 3, which shows a poor response to TAE.