Plasma CEA, tumor CEA, and tumor histology

Carcinoembryonic antigen (CEA) has been thought to be a diagnostic and prognostic indicator of colorectal cancer. Initial descriptions of CEA as a tumor specific antigen suggests a relationship between tumor CEA and circulating plasma CEA. To define the relationship between CEA and colorectal carcinoma, we have studied the CEA concentration of preoperative plasma, tumor tissue, and normal bowel distant from tumor in 35 patients who had clinically curative resections. Tumor histology was evaluated for Dukes class, histologic grade, necrosis, and vessel invasion. Regression analysis yielded no evidence of correlation between tumor CEA and plasma CEA. No correlation could be shown between tumor concentration of CEA and the histological parameters previously noted. CEA was found in all specimens of normal bowel. Furthermore, in 34% of the cases studied, the tumor CEA was not significantly higher than in normal bowel. No significant difference was shown when histopathological findings were compared to normal and abnormal plasma CEA values. These findings suggest the following conclusions: CEA is not tumor specific. Increased levels of CEA in tumor tissue are not a constant finding in colorectal carcinoma. Tumor levels of CEA do not appear to correlate with histologic degree of tumor differentiation. Elevated plasma levels of CEA do not necessarily connote elevated tumor tissue levels of CEA, and conversely, normal plasma levels of CEA do not necessarily mean low levels of tumor CEA.