Abstract
In order to clarify the pathomorphological characteristics of the capsule and fibrous septum of hepatocellular carcinoma (HCC), 47 surgically resected HCCs smaller than 3cm in diameter were studied grossly and histologically. Grossly, the majority of the resected HCCs shows an expansive growth pattern. Thirty six out of 47 the cases (76.6%) were single nodular type with or without perinodular tumor growth. Thin fibrous capsule and fibrous septa were observed in 29 (61.7%) and 38 cases (80.9%), respectively. Both capsule and septum were found in 26 cases (55.3%). Among 7 HCCs smaller than 1cm in diameter, the capsule and septum were seen only in one case, respectively. Thus, the capsule and septum of HCC seem to be formed when the tumor size reaches around 1.5cm in diameter in most cases. According to the fact that more thantwo-third of small HCC have the capsule and/or the septum, the imaging demonstration of them in space occupying lesions of the liver is quite helpful in diagnosis of HCC.
Three possible mechanisms were considered in the septum formation in HCC. Type 1. Engulfing of the old capsule within the tumor following extra-capsular tumor growth. Type 2. Condensation of fibrous components at the boundary of cancerous tissues exhibiting different histologic features. Type 3. In confluent multinodular tumor, fibrous stromas between each tumor nodule are retained within the tumor as the septum when tumors become confluent. Among the 38 resected HCCs with septum, Type 1 septum was seen in 24 cases (63.2%) and was the most common.
