The value of monoclonal antibody B72.3 for the diagnosis of breast carcinoma: experience with the first commercially available source.

One hundred cases of invasive breast carcinoma were studied using the commercially available monoclonal antibody Anti-Human Tumor-Associated Glycoprotein-72 (MAb B72.3, Biomedical Technologies Inc, Stoughton, MA) prediluted at 8.5 micrograms/mL. Forty-three cases displayed positive reactivity with this antibody. Intensity and distribution of positive staining varied among the tumor cells. Twenty-two cases had 1% or less reactive cells, while eight cases contained 40% or more positive tumor cells. Apical cell membrane and diffuse cytoplasmic staining were present. In fifteen cases intracytoplasmic lumina and extra-cellular secretory material were highlighted by positive staining. Thirty-five cases had benign breast tissue adjacent to the tumor. Benign ductal and lobular epithelial cells were nonreactive except for two cases in which small foci of apocrine metaplasia were positive. Reactivity with MAb B72.3 was not dependent upon histologic grade, nuclear grade, nodal status, or patient age. Excluding the lower number of positively stained cases, our findings were similar to other MAb B72.3 investigations. The number of positively stained cases and the intensity of the positivity were increased by using MAb B72.3 at 5.0 micrograms/mL with overnight incubation, or by using MAb B72.3 at 40.0 micrograms/mL with 2 hours of incubation. Our findings confirm that MAb B72.3 shows reliable reactivity with breast carcinoma that is sensitive to antibody concentration and incubation time without loss of specificity for tumor cells. Our results are also consistent with the view that MAb B72.3 probably detects epithelial membrane-related antigens in breast carcinoma, as do several other antibodies.