Histology and Cytometrics in Human Breast Cancers Assayed for the Presence of Prolactin Receptors

: Histology and cytometrics were evaluated in 50 cases of human breast infiltrating carcinomas (44 ductal, 6 lobular) assayed for the presence of prolactin receptors (PR). The tumors were considered PR positive when the level of specific binding reached or exceeded 0.5%. Twenty-six ductal infiltrating carcinomas and 4 lobular ones were PR positive. No strict correlation was found between PR and degree of histologic differentiation (expressed in grades) or menopausal status. Better differentiated (grade I) ductal carcinomas were, however, mostly PR negative. Evaluation of the mean nuclear diameter (MND) and of the maximal epithelial cellularity (MEC) revealed that in ductal carcinomas a high level of PR (greater than 3% specific binding) was significantly correlated with a high MND. It is concluded that, contrary to that observed in estrogen receptor-positive tumors, PR-positive human ductal carcinomas are more likely to have large nuclei, i.e., cytologically anaplastic, whereas better differentiated (grade I) carcinomas are generally PR negative.