Predictive classification of human breast carcinomas based on lactalbumin synthesis.

The milk protein lactalbumin was found in the cytosol fraction of 20 of 53 human breast carcinomas. Oestrogen receptor (E.R) was detected in 36 of the tumours. The presence of lactalbumin was closely associated with the presence of E.R.; in tumours containing both, there was a positive linear correlation between concentrations of lactalbumin and E.R. Synthesis of lactalbumin by a mammary carcinoma seems to indicate an intact oestrogen receptor mechanism and may therefore be useful in identifying tumours responsive to endocrine therapy.