Variation of estrogen and progesterone receptor status in breast cancer

In a series of fifty breast cancer patients two estrogen and progesterone receptor assays were performed. In two simultaneous assays (tissue samples taken at the same time) disordant results in estrogen receptor, progesterone receptor and double receptor status were detected in 12%, 12% and 21% of cases respectively. In sequential assays (tissue samples taken with an interval between the samples) this variation was more pronounced, 24%, 36% and 36% respectively. The variation in simultaneous assays was similar between two samples of the same primary tumour as between samples from a primary tumour and a metastasis. In sequential assays there was no difference in the time between assays in concordant and discordant samples. The variation in receptor status is said to be due to the heterogeneity within the primary tumour.