Ultrasonography (US) and computed tomography (CT) are the most effective screening methodologies for hepatocellular carcinoma (HCC). In our US screening, 20% of small HCC nodules less than 20 mm in diameter were detected as hyperechoic tumors. Among these hyperechoic HCC nodules, we have often observed (BL) which is defined as hypoechoic nodules in the hyperechoic tumor. In this study, we report that the BL is a sign of dedifferentiation of early stage of HCC with fatty change by US. From 1994 to 1998, we performed tumor targeting needle biopsy in 938 hepatic nodular lesions. Among them, 284 nodules <20 mm in diameter, histologically diagnosed as HCC, were studied. BL is defined as a hyperechoic tumor containing a hypoechoic nodule >4 mm in diameter by US. Among 284 nodules, well, moderately and poorly differentiated HCC were 183 (64.4%), 100 (35.2%) and 1 (0.4%), respectively. On US, hypoechoic, isoechoic, and hyperechoic nodules were 188 (66.2%), 32 (11.3%) and 64 (22.5%), respectively. Forty-seven nodules of 64 hyperechoic HCC nodules <20 mm in diameter, 47 nodules (73.4%) showed fatty changes. Of 64 hyperechoic HCC nodules, we recognized 22 nodules (34.4%) as BL. The proportion of BL type hyperechoic nodules increased with the tumor size. Two hyperechoic nodules followed by US changed to BL with tumor enlargement. Histologic examination of a resected HCC with BL showed that hyperechoic HCC nodule represented well-differentiated HCC with fatty change and inner hypoechoic lesion represented moderately differentiated HCC without fatty change. In US screening for HCC, BL was often observed in HCC nodules from 11 to 20 mm in diameter. Histologic examination revealed that BL of HCC on US was associated with tumor progression and indicated dedifferentiation showing moderately differentiated HCC in well-differentiated HCC with fatty change.
