Alpha-fetoprotein-producing gastric carcinoma presenting focal hepatoid differentiation in metastatic lymph nodes

Hepatoid adenocarcinoma (HA) is a rare variant of adenocarcinoma of the stomach, which is clinically characterized by increased level of serum alpha-fetoprotein (AFP) and poor prognosis. Microscopic findings include both adenocarcinomatous and hepatoid elements. A case of gastric adenocarcinoma with focal hepatoid differentiation confined within the metastatic lymph nodes occurred in a 55-year-old woman, who developed an advanced gastric carcinoma composed entirely of a typical papillo-tubular adenocarcinoma. Metastatic tumors were present in 8 of 13 perigastric lymph nodes, and 3 of these showed medullary and trabecular tumour growth reminiscent of hepatocellular carcinoma with immunohistochemical positivity for AFP. Preoperative serum AFP was 630 ng/ml and dropped to 76 ng/ml 2 weeks after the operation. Microscopic and immunohistochemical studies on the entire primary tumour tissue failed to demonstrate a focus of hepatoid or an AFP-positive area. This suggests that elevation of serum AFP may be reflected by focal hepatoid differentiation only in the metastatic lymph nodes, requiring extensive evaluation of the metastatic tumour in regional lymph nodes in the case of AFP-producing gastric carcinoma.