title: The PAS positive material in gastric cancer cells of signet ring type is not mucin.
abstract: OBJECTIVE
  The purpose of this study is to assess the exocrine and neuroendocrine properties of tumour cells in diffuse gastric cancer with signet ring cell differentiation.
  
  
  METHODS
  Mucin mRNA and protein expressions (MUC1, 2, 3, 4, 5AC, 6 and MUC13) were assessed by immunohistochemistry and in situ hybridization. The neuroendocrine properties were evaluated by protein and mRNA expression of the general neuroendocrine markers chromogranin A and synaptophysin.
  
  
  RESULTS
  No MUC expression was observed in signet ring tumour cells including the amorphous substance in any of the nine cases. All cases showed immunoreactivity to synaptophysin, and seven out of nine cases immunoreactivity to chromogranin A in signet ring and non-signet ring tumour cells. Chromogranin A mRNA expression was observed in tumour cells in all samples with retained mRNA.
  
  
  CONCLUSIONS
  The lack of MUC protein and mRNA in signet ring tumour cells suggests the amorphous substance is not mucin. The lack of MUC mRNA expression in non-signet ring tumour cells questions exocrine differentiation in this tumour group. The abundant protein expression of the general neuroendocrine markers CgA and synaptophysin, and mRNA expression in tumour cells strengthens the hypothesis that this tumour group may be of neuroendocrine origin.
authors.affiliation: Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway. Electronic address: oystein.sordal@ntnu.no.
authors.forename: Øystein
authors.initials: Ø
authors.lastname: Sørdal
authors.affiliation: Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway; Department of Gastroenterology and Hepatology, St. Olavs University Hospital, Trondheim, Norway.
authors.forename: Gunnar
authors.initials: G
authors.lastname: Qvigstad
authors.affiliation: Department of Pathology and Medical Genetics, St. Olavs University Hospital, Trondheim, Norway; Department of Laboratory Medicine, Children and Woman Health, NTNU, Trondheim, Norway.
authors.forename: Ivar Skjåk
authors.initials: IS
authors.lastname: Nordrum
authors.affiliation: Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway; Department of Gastroenterology and Hepatology, St. Olavs University Hospital, Trondheim, Norway.
authors.forename: Arne K
authors.initials: AK
authors.lastname: Sandvik
authors.affiliation: Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway; Department of Gastroenterology and Hepatology, St. Olavs University Hospital, Trondheim, Norway.
authors.forename: Bjørn I
authors.initials: BI
authors.lastname: Gustafsson
authors.affiliation: Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway; Department of Gastroenterology and Hepatology, St. Olavs University Hospital, Trondheim, Norway.
authors.forename: Helge
authors.initials: H
authors.lastname: Waldum
mesh_terms: D014408:Biomarkers, Tumor / Q000378:metabolism; D018279:Carcinoma, Signet Ring Cell / Q000378:metabolism*; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D053379:Chromogranin A / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D009077:Mucins / Q000378:metabolism*; D010503:Periodic Acid-Schiff Reaction; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013274:Stomach Neoplasms / Q000378:metabolism*; D016708:Synaptophysin / Q000378:metabolism
chemical_list: D014408:Biomarkers, Tumor; D053379:Chromogranin A; D009077:Mucins; D012333:RNA, Messenger; D016708:Synaptophysin
keywords: Mucin; Neuroendocrine; Signet ring cell