Pathologic features of small hepatocellular carcinoma.

Twenty-one nodules of small hepatocellular carcinoma (HCC) were examined. Histologically, the nodules often presented formation of plump trabeculae, marked nuclear atypism, or aggressive growth comprising capsular invasion, vascular invasion, and replacement of adjacent pseudolobules. Aside from these characteristic findings of HCC, it was important to reveal the following features for the diagnosis of well differentiated type of small HCC: variable thickening or distortion of trabecular structure in association with nuclear crowding, acinar formation, selective cytoplasmic accumulation of Mallory bodies, nuclear abnormalities consisting of thickening of nucleolus, hepatic cords in close contact with bile ducts or blood vessels, and hepatocytes growing in a fibrous environment. During the invasive growth, the tumor cells may well be subtly blended with benign hepatocytes, giving rise to a pattern of "mixed cellularity". It is also emphasized that connective tissue septa of pseudolobules could be a route of rapid tumor spreading.