Peritoneal seeding of hepatocellular carcinoma: clinicopathological characteristics of 17 autopsy cases.

Peritoneal seeding (PS) of hepatocellular carcinoma (HCC) is uncommon, and the clinicopathological features are poorly understood. A total of 181 autopsy cases of HCC, including 171 cases with detailed clinical information, was investigated for PS and evaluated. PS was identified in 17 cases (9.4%), and was locally (70.6%) or entirely (29.4%) distributed in the peritoneal cavity, involving the diaphragm (76.5%), omentum (47.1%), or alimentary tract serosa (47.1%). Compared with primary HCC, PS showed similar or slightly undifferentiated features (88.2%) and exhibited more differentiated features (11.8%). In 15 cases (88.2%) of HCC with PS, primary HCC showed membranous β-catenin immunoreactivity. However, in five cases (33.3%), respective PS lost this immunoreactivity. PS was significantly associated with rupture of HCC (P= 0.012), direct diaphragmatic invasion (P= 0.001), and lymph node metastasis (P < 0.001), indicating these are high risk factors for PS; there was no significant association with a past history of percutaneous fine-needle biopsy, percutaneous ethanol injection and/or radiofrequency ablation (P= 0.97), or metastasis to lung (P= 0.13), bone (P= 0.71), or adrenal gland (P= 0.79). PS can infrequently proliferate aggressively with more differentiated features. Loss of membranous β-catenin expression may be associated with PS of HCC.