Gastrointestinal cancer-associated antigen CA 19-9 in histological specimens of pancreatic tumours and pancreatitis

The expression of the gastrointestinal cancer associated antigen CA 19-9, defined by the monoclonal antibody 1116 NS 19-9, was studied by immunoperoxidase staining in routine formalin-fixed, paraffin-embedded tissue sections from normal pancreata, pancreata with pancreatitis and from benign and malignant pancreatic neoplasms. The formalin-fixed specimens were treated with pepsin, which enhanced the staining intensity. Eighty-five per cent of well to moderately differentiated adenocarcinomas were positive. The staining was most intense in the apical border of cells lining the lumina of malignant glands, and in mucus inside the lumina, but cytoplasmic staining was also seen. In poorly differentiated adenocarcinomas the number of positive cells was smaller and in anaplastic carcinomas only occasional cells were stained. All mucinous cystadenomas and cystadenocarcinomas stained intensely, whereas serous cystadenomas, and all benign and malignant islet cell tumours were negative. Ducts in chronic pancreatitis and in normal pancreata were positive in 96% and 79%, respectively, but the staining was focal and usually weaker than in carcinomas. In acute pancreatitis (92% positive) the staining was more intense, and the CA 19-9 expression was seen predominantly in small terminal ducts and in centroacinar cells. There was an apparent correlation between the degree of differentiation of the ductal adenocarcinomas and the expression of CA 19-9, whereas the correlation between tissue expression and serum levels of CA 19-9 was poor.