The distribution and localization of the monoclonal antibody-defined antigen 19-9 (CA19-9) in chronic pancreatitis and pancreatic carcinoma. An immunohistochemical study.

The carbohydrate antigen 19-9 (CA19-9) is considered to be of great importance in the diagnosis, differential diagnosis and follow-up of human pancreatic carcinoma. CA19-9 antigen has been isolated and characterized as the oligosaccharide sialylazed lacto-N-fucopentaose II and a monoclonal antibody against CA19-9 is commercially available. In this immunochemical study we have examined the localisation and distribution of monoclonal anti-CA19-9 in pancreatic tissue obtained from 20 patients with a normal pancreas (lacking pancreatic tumour or evidence of inflammation), from 50 patients with chronic pancreatitis and from 50 patients with pancreatic carcinomas of various types. In the normal pancreas (free from tumour or inflammation) we found anti-CA19-9 to be localized in the branches of the pancreatic ducts with discontinuities predominantly at the apical surfaces of the lining epithelium. In chronic pancreatitis a continuous positive reaction was found in the small, medium and large ramifications of the pancreatic ducts. In ductal epithelium exhibiting mucoid transformation, a mosaic-like, discontinuous positive reaction was found, whereas in epithelium showing pseudopapillary and papillary hyperplasia a uniform positive reaction was obtained. Multilayered epithelium ("squamous metaplasia") was negative. The fluid content of any cysts present and the tubular accumulations found in chronic pancreatitis showed a positive reaction. The reaction in chronic pancreatitis differed from that in normal pancreas in its distribution but not in its intensity. All carcinomas of the exocrine pancreas showed intensely positive reaction in a very varied distribution whereas the anaplastic carcinomas gave a negative reaction. Whilst in chronic pancreatitis the binding of anti-CA19-9 was unimpressive and strictly localized, in exocrine pancreatic carcinomas binding was and strictly localized, in exocrine pancreatic carcinomas binding was very marked and diffuse in distribution. From this we conclude that malignant cells display a greater number of CA19-9 epitopes than cells in chronic pancreatitis. The difference can only be regarded as quantitative, since the immunohistochemical reaction does not allow qualitative discrimination between chronic pancreatitis and pancreatic carcinoma; CA19-9 should not be therefore termed a "tumour marker". The glycoprotein nature of CA19-9 was confirmed by sialidase and chemical desialylation.