Hepatoid or α-fetoprotein (AFP)-producing adenocarcinomas of stomach growing in a solid pattern are highly aggressive tumors. It is difficult to detect hepatoid differentiation solely based on findings from hematoxylin and eosin stainings, especially in small biopsy specimens. Gastric adenocarcinomas with hepatoid differentiation should be distinguished from solid-type gastric adenocarcinoma because of their different biological behavior. We immunohistochemically analyzed hepatocellular markers (AFP, glypican 3, and Hepatocyte paraffin 1 [HepPar-1]) and possible markers of gastric hepatoid adenocarcinoma (Sal-like protein 4 [SALL4] and palate, lung, and nasal epithelium carcinoma-associated protein [PLUNC]) to detect hepatoid differentiation in 45 gastric hepatoid adenocarcinomas and 47 nonhepatoid solid-type poorly differentiated adenocarcinomas. There were a higher incidence of vascular invasion (P =.0055) and distant metastasis (P =.0458) in hepatoid adenocarcinoma than in nonhepatoid adenocarcinoma. AFP, SALL4, HepPar-1, and glypican 3 were significantly higher in hepatoid adenocarcinoma than in nonhepatoid adenocarcinoma. All 5 markers were positive in both the hepatoid/solid and the tubular component. In hepatoid adenocarcinoma, the frequency of distant metastasis was significantly higher in SALL4-negative cases than in SALL4-positive cases (P =.0381). HepPar-1 was associated with liver metastasis (P =.0452). PLUNC was correlated with lymph node metastasis (P =.0375). There was a significant difference in the survival rate between HepPar-1-positive and HepPar-1-negative groups (P =.0437). The coexpression of PLUNC and SALL4 and the other coexpression of HepPar-1 and PLUNC were associated with poorer prognosis (P =.0181 and P =.0443, respectively). AFP, SALL4, HepPar-1, and glypican 3 are useful for the detection of hepatoid differentiation. A combination of PLUNC, HepPar-1, and SALL4 could be a reliable prognostic indicator in hepatoid adenocarcinoma of the stomach.
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