Simultaneous hepatocyte paraffin-1–positive α-fetoprotein–producing gastric adenocarcinoma and gastric mucosal-associated lymphoid tissue

An 85-year-old Japanese woman was admitted to our hospital because of abdominal fullness. Computed tomography revealed multiple nodules in the liver; the interpretation was metastatic carcinoma. Serum laboratory test revealed extremely elevated α-fetoprotein (AFP) (8820 ng/mL; normal, <10 ng/mL). Upper and lower gastrointestinal endoscopy was performed and identified a large type-2 advanced gastric carcinoma and mucosal irregularity of the antrum. Biopsies were performed. The gastric carcinoma was well-differentiated papillotubular adenocarcinoma. Immunohistochemically, it was positive for pancytokeratins, AFP, hepatocyte paraffin-1 (HepPar1), p53 protein, and Ki-67 antigen (labeling, 70%) but was negative for vimentin, CEA, CA19-9, and lymphoid cell markers. Therefore, the lesion was diagnosed as AFP-producing gastric carcinoma with HepPar1 positivity. The biopsies of the gastric mucosal irregularity revealed severe lymphoid infiltration. The lymphoid cells were centrocyteslike cells with plasma cell differentiation and, immunohistochemically, were composed of CD20-positive B cells. A small number of CD3-positive T cells were also seen. Lymphoepithelial lesions were recognized. Therefore, the lesion was diagnosed as mucosal-associated lymphoid tissue lymphoma. Helicobactor pylori were recognized on Giemsa stain. The present case showed that AFP-producing gastric adenocarcinoma and mucosal-associated lymphoid tissue lymphoma can coexist. They may be associated with H. pylori infection. It was also interesting that the AFP-producing gastric carcinoma expressed HepPar1.