Measuring of immunoreactivity of carcinoembryonic antigen (CEA) in colorectal cancer by microdensitometry.

In 32 patients with colorectal carcinomas, the immunoreactivity of carcinoembryonic antigen (CEA) was measured on section preparations of the tumours by means of a computer controlled microdensitometric method. By measuring numerous single points, the intensity of the immunohistochemical staining reaction of CEA was evaluated. This method is superior to the commonly used semiquantitative method (+, ++, ) for the assessment of various degrees of staining intensity whenever the antigen to be measured is not homogeneously dispersed in the tissue. The results show that highly differentiated colorectal carcinomas of stage A according to Dukes classification have a lower CEA immunoreactivity than highly differentiated carcinomas of stage B. A correlation between CEA immunoreactivity and degree of malignancy could only be found in patients in stage B. Stage C carcinomas of all degrees of differentiation appeared with a very low CEA immunoreactivity. CEA follow-up controls in our study were of little value for detecting local recurrences; metastases, however, almost always caused an increase in serum CEA titers. Prognostically, a preoperatively increased serum CEA level seems to be as unfavourable as a low CEA immunoreactivity in the tumour.