Encyclopedia / C / Carcinoembryonic Antigen

Carcinoembryonic Antigen


Carcinoembryonic antigen (CEA) is an antigen (protein) present in very small quantities in adult tissue. A greater than normal amount may be suggestive of cancer. Normally, its values range from 0.0 to 2.5 nanograms per milliliter of serum (from blood), in non-smokers. CEA levels are higher, on average, in men, smokers, and older individuals.

Tests for its presence aid in screening, in evaluating recurrent or disseminated disease, and in gauging the success of surgical removal of malignant tumors.


CEA is a substance normally found in a fetus which, when found at elevated levels in the blood of adults, may indicate the presence of colorectal cancer or other types of cancer. CEA is therefore called a tumor marker.

It has been used to monitor patients for the recurrence of a number of different cancers, including breast, thyroid, lung, ovarian, pancreatic, stomach, and colon/rectal. It is also referred to as an "oncofetal antigen" because of its similarity to fetal tissue.

CEA levels can also be an indication of the effectiveness of treatment.


Why are you recommending a CEA test?

If the CEA level is low or normal does it positively rule out a tumor?

What are the chances of a false CEA reading?

If this could possibly indicate the presence of a tumor, what tests need to be done to determine where?