Influence of tissue heterogeneity on the determination of steroid receptors in breast cancer.

Biochemical determination of hormone receptors in carcinomas is influenced by the potential heterogeneity of the tissue samples. In order to check this, samples of 16 breast cancers were divided into 6 segments. These segments were alternately examined for their ratio of tumor tissue to connective tissue ("percentage of carcinoma") or for the content of estrogen and progesterone receptors. Only 3 of the tumors were homogeneous, and 9 of the heterogeneous tissues had hormone receptors. The segment with the maximum "percentage of carcinoma" was adjacent to that with the peak value of hormone receptors in all but 1 tissue. The same applied to the minima. The maximum and minimum values of estrogen and progesterone receptors were located within the same segment in all but one tissue sample. The results demonstrated that biochemical assay of hormone receptors is reliable. A reduction of the sample volume does not enhance the precision of the receptor assay, since it increases the possibility of a false negative result.