Simultaneous Assay of ErbB-2 Protein and Carcinoembryonic Antigen in Cyst Fluid as an Aid in Diagnosing Cystic Lesions of the Breast.

C-erbB-2 oncoprotein (ErbB-2 protein)and carcinoembryonic antigen (CEA)were simultaneously evaluated in the breast cyst fluid of 6 patients with intracystic cancer, 6 patients with intracystic papilloma, and 42 patients with gross cystic disease. A combination test, using 12 ng of ErbB-2 protein and 150 ng of CEA/ml of cyst fluid, respectively, as cutoff values resulted in a positive detection rate of 83%(5/6 cases) for intracystic breast cancer. Two of the 6 patients with intracystic papilloma and 2 of the 42 patients with gross cystic disease were positive. In addition, elevated levels of these markers in cyst fluid correlated well with the expression of these antigens in the corresponding tumor. Thus, it can be concluded that measurements of ErbB-2 protein and CEA aid in the diagnosis of intracystic breast cancer, and the assay of ErbB-2 protein is valuable for detecting tumors in which this protein is overexpressed.