Diagnostic value of a second generation CA 15-3 antibody to detect adenocarcinoma in body cavity effusions

Detecting malignant cells in body cavity effusions can be diagnostically challenging. Several monoclonal antibodies have been studied to improve the diagnostic yield of effusion cytology but without widespread acceptance. The CA 15-3 antibody has demonstrated high sensitivity but limited specificity for breast carcinoma in surgical pathology. A second generation CA 15-3 antibody has been developed that has not been studied in serous effusions to the authors' knowledge. The authors examined this second generation CA 15-3 antibody for its diagnostic utility in detecting adenocarcinomas in this cytologic setting.

Cell block material from 114 cases of unequivocally benign or malignant body cavity effusions were studied. Slides were stained for CA 15-3 by using the avidin-biotin complex method. The percentage of cells exhibiting strong staining was estimated both for breast carcinoma and for all adenocarcinomas as a group. These results were compared with CA 15-3 staining exhibited by benign mesothelium.

CA 15-3 was expressed in at least 10% of tumor cells in 97% of breast carcinoma cases and in 90% of adenocarcinomas overall. The highest sensitivity was observed in carcinomas of the breast, ovary, and lung. Of 40 cases of benign mesothelium, only 4 (10%) were positive (P < 0.001). The sensitivity of CA 15-3 was 97% for breast carcinoma and 91% for adenocarcinomas overall. Specificity was 95% for breast carcinoma and 91% for adenocarcinomas.

CA 15-3 is an immunostain with high specificity and sensitivity for adenocarcinomas in cell block material from effusions. The antibody holds particular promise for detecting breast carcinoma. Cancer (Cancer Cytopathol)