Peroxidase activity in human breast carcinomas: correlation with histological and biochemical parameters.

Peroxidase activity was found in 68% of 56 human breast carcinomas. Median activity was higher in ductal carcinomas than in tumors with lobular components. Activity did not correlate with tumor grade or stage, or the presence or absence of axillary node involvement. Activity, however, correlated with tumor cellularity, lymphocyte infiltration levels, and total protein and alkaline phosphatase levels. It is concluded that variation in peroxidase activity in human breast tumors is at least in part due to lymphocyte infiltration. Furthermore, this contamination of breast tumors with lymphocytes may explain the lack of correlation between estradiol receptor levels and peroxidase activity.