A mucinous-like carcinoma-associated antigen (MCA) in the tissue and blood of patients with primary breast cancer.

The monoclonal antibody (MAb) b12 raised against human breast cancer cell lines was found to identify an epitope of a mucinous-like carcinoma associated antigen (MCA) that is strongly represented on breast tumor cells. The b12 MAb was used to develop an enzyme immunoassay (EIA) kit. MCA levels were measured with the EIA method in the cytosol of both breast cancer and normal breast tissue as well as in the blood of 147 patients with primary breast cancer and 92 healthy subjects. MCA cytosol levels were significantly higher in carcinoma than in normal breast tissue cytosol samples. Higher MCA levels were found in the cytosol of tumor without lymph nodal involvement. The 95th percentile of the MCA value distribution in the healthy control group (11.0 U/ml) was chosen as negative/positive cut-off level. The overall positivity rate in breast cancer group was 26.5% with MCA showing a trend toward higher levels in patients with more advanced disease. Significantly higher levels were found in patients with a higher number of positive lymph nodes.