Glypican-3 as a useful diagnostic marker that distinguishes hepatocellular carcinoma from benign hepatocellular mass lesions.

Context: Histopathologic distinction between hepatocellular carcinoma (HCC) and benign hepatocellular mass lesions, particularly hepatocellular adenoma, can sometimes be challenging. The currently available ancillary tools are suboptimal in terms of sensitivity and specificity.
Objective: To further characterize the diagnostic value of glypican-3 (GPC3), a cell surface proteoglycan that has recently been shown to be overexpressed in HCC, in the distinction between HCC and benign hepatocellular mass lesions.
Design: A total of 221 surgically resected liver specimens were subjected to immunohistochemical staining using a monoclonal antibody specific for GPC3. These included 111 HCCs, 48 hepatocellular adenomas, 30 focal nodular hyperplasias, and 32 large regenerative nodules in the background of cirrhosis.
Results: Cytoplasmic, membranous, and canalicular staining for GPC3 was detected in 84 (75.7%) of the 111 HCCs, among which, 61 (72.6%) of the 84 cases exhibited diffuse immunoreactivity. In contrast, none of the 110 cases of hepatocellular adenoma, focal nodular hyperplasia, and large regenerative nodule showed detectable GPC3 staining. Focal GPC3 immunoreactivity was detected in cirrhotic nodules in 11 (16.4%) of 67 HCC cases with a cirrhotic background, but no background staining was observed in the remaining 44 HCCs without cirrhosis. GPC3 expression in HCCs did not correlate with the size, differentiation, or stage of the tumors; the presence or absence of cirrhotic background; or the underlying etiologies.
Conclusions: GPC3 is a specific immunomarker for HCC that can be used to distinguish HCC from benign hepatocellular mass lesions, particularly hepatocellular adenoma. However, the diagnosis of HCC should not rely entirely on positive GPC3 immunostaining because focal immunoreactivity can be detected in a small subset of cirrhotic nodules. In addition, GPC3 expression in HCC can also be focal, and thus, the lack of GPC3 staining does not exclude the diagnosis of HCC.