title: The prevalence of pancreatic acinar differentiation in gastric adenocarcinoma:  report of a case and immunohistochemical study of 111 additional cases.
abstract: Although pancreatic acinar metaplasia in the gastric mucosa is well recognized in chronic gastritis, gastric carcinoma with acinar differentiation is very rare. We encountered a case of gastric adenocarcinoma with prominent histologic and immunohistochemical features of pancreatic acinar differentiation in the absence of identifiable heterotopic pancreatic tissue. Distinct glandular and diffuse patterns of adenocarcinoma were also present, and there was focal mucin production. The tumor strongly expressed pancreatic exocrine enzymes trypsin and chymotrypsin, and focal neuroendocrine staining was also present. To investigate the prevalence of acinar differentiation in histologically typical gastric cancers, we performed immunohistochemical staining for trypsin and chymotrypsin on a tissue microarray containing 111 conventional gastric adenocarcinomas (60 intestinal, 28 mixed, 22 diffuse type, and 1 undifferentiated). No obvious morphologic evidence of acinar differentiation was identified in any of the 111 cases. Although some cases showed equivocal staining for at least 1 pancreatic exocrine enzyme on the initial tissue microarray sections, repeat immunohistochemical staining on representative whole-tissue sections failed to reproduce positive staining. Thus, acinar differentiation is rare in gastric adenocarcinomas, other than in histologically unusual cases such as the one we report, and in others from the literature, which are reviewed.
authors.affiliation: Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA.
authors.forename: Hwajeong
authors.initials: H
authors.lastname: Lee
authors.forename: Laura H
authors.initials: LH
authors.lastname: Tang
authors.forename: Emanuela F
authors.initials: EF
authors.lastname: Veras
authors.forename: David S
authors.initials: DS
authors.lastname: Klimstra
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000032:analysis*; D001706:Biopsy; D018267:Carcinoma, Acinar Cell / Q000201:enzymology* / Q000473:pathology* / Q000601:surgery; D002454:Cell Differentiation; D002918:Chymotrypsin / Q000032:analysis*; D005260:Female; D005743:Gastrectomy; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008679:Metaplasia; D008875:Middle Aged; D013274:Stomach Neoplasms / Q000201:enzymology* / Q000473:pathology* / Q000601:surgery; D046888:Tissue Array Analysis; D014357:Trypsin / Q000032:analysis*
chemical_list: D014408:Biomarkers, Tumor; D002918:Chymotrypsin; D014357:Trypsin