Test Catalog

Test ID: C2729    
Breast Carcinoma-Associated Antigen, Serum

Useful For Suggests clinical disorders or settings where the test may be helpful

Serial testing in women with prior stage II or III breast cancer who are clinically free of disease


Predicting early recurrence of disease in women with treated carcinoma of the breast


Indicating that additional tests or procedures should be performed to confirm recurrence of breast cancer


This test is not useful for screening women for carcinoma of the breast.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Carcinoma of the breast is the most prevalent form of cancer in women. These tumors often produce mucinous antigens, which are large-molecular-weight glycoproteins with O-linked oligosaccharide chains.


Monoclonal antibodies directed against these antigens have been developed, and several immunoassays are available to quantitate the levels of tumor-associated mucinous antigens in serum. The antibodies recognize epitopes of a breast cancer-associated antigen encoded by the human mucin 1 (MUC-1) gene, which is known by several names including MAM6, milk mucin antigen, cancer antigen (CA) 27.29, and CA 15-3.


While CA 27.29 is expressed at the apical surface of normal epithelial cells, it is present throughout malignant epithelial cells of the breast, lung, ovary, pancreas, and other sites. The cancer-associated form of the antigen is less extensively glycosylated than the normal form and more specific for tumor cells.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.


> or =18 years: < or =38.0 U/mL (use not defined)


> or =18 years: < or =38.0 U/mL

Reference values have not been established for patients who are <18 years of age.

Serum markers are not specific for malignancy, and values may vary by method.

Interpretation Provides information to assist in interpretation of the test results

Increased levels of cancer-associated antigen (CA 27.29) (>38 U/mL) may indicate recurrent disease in a woman with treated breast carcinoma.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

At this time, this test provides results for female patients only.


The use of cancer-associated antigen (CA 27.29) has not been demonstrated to provide clinical benefit to these patients, which has led some Mayo clinical investigators to conclude there is insufficient justification for routine clinical use of this new marker.


Some patients who have been exposed to mouse antigens, either in the environment or as part of treatment or imaging procedure, may have circulating antimouse antibodies present. These antibodies may interfere with the assay reagents to produce unreliable CA 27.29 results.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Bon GG, Von Mensdorff-Pouilly S, Kenemans P, et al: Clinical and technical evaluation of ACS BR serum assay of MUC1 gene-derived glycoprotein in breast cancer, and comparison with CA 15-3 assays. Clin Chem. 1997;43:585-593

2. Chan DW, Beveridge RA, Muss H, et al: Use of Truquant BR radioimmunoassay for early detection of breast cancer recurrence in patients with stage II and stage III disease. J Clin Oncol. 1997;15:2322-2328

3. Lin DC, Genzen JR: Concordance analysis of paired cancer antigen (CA) 15-3 and 27.29 testing. Breast Cancer Research and Treatment. 2018;167:269-276