Tissue polypeptide antigen and carcinoembryonic antigen in colon tumors: serum levels and immunohistochemical localization.

Patients with malignant and benign colon disease (59 colon cancer and 96 polyps) were studied by means of tissue polypeptide antigen (TPA) and carcinoembryonic antigen (CEA) tests. The evaluation of the circulating levels of the markers showed that the overall sensitivity for the TPA test was 57.6% and for the CEA test was 55.9%. Their specificities were 89.5% and 94.7%, respectively. The analysis of results indicated no considerable difference between CEA and TPA in detecting individuals with malignant diseases. There was only a slight difference in Dukes stages: in stages A and B, TPA sensitivity was higher than CEA sensitivity. On the contrary, in the group of patients with polyps, more false-positive results were obtained with the TPA test than with the CEA test. Immunohistochemical studies on the small group of patients (12 colon cancers) allowed us to evaluate the relationship between the staining positivity for the anti-TPA and anti-CEA antibodies and the circulating levels of the markers. The staining in some cases was not correlated either with the stage of cancer or the circulating TPA or CEA levels. This fact further shows the need to investigate the mechanism that determines the blood levels of many tumor markers. All the specimens examined were positive for TPA and CEA staining, but they were composed of varying proportion of positive and negative tumor cells. The degree of positivity was frequently variable not only between the specimens but also within the same specimen.