The key features favoring metastatic adenocarcinoma over HCC are columnar cells with polar nuclei, acinar formation, and evidence of mucin production. The key features favoring primary HCC are polygonal cells with granular cytoplasm, central nuclei, balls of cells with endothelial wrapping and transgressing vessels. Intranuclear cytoplasmic invaginations are more common in HCC than in metastatic carcinomas but also are common in benign hepatocytes. Hyaline bodies are much more common in HCC than in metastatic tumors. Mucin production favors metastatic adenocarcinoma but does not completely exclude HCC. Elevated serum levels or cellular expression of AFP favors HCC. Elevated serum levels or cellular expression in HCC. A diffuse pattern of cytoplasmic CEA staining is typical of adenocarcinomas, while HCC characteristically shows a predominantly pericanalicular pattern (unique to benign or malignant liver cells).