Changes in estrogen and progesterone receptor content of primary breast carcinoma during the menstrual cycle.

This study was undertaken to determine if hormone receptor activity in breast cancers changes during different phases of the menstrual cycle. Estrogen (ER) and progesterone (PgR) receptors in seventy-eight primary breast carcinomas from premenopausal women were compared with the phase of the menstrual cycle at the time of biopsy. The frequency of ER positivity did not change, but PgR positivity became significantly higher after the early follicular phase. An increase in mean ER and PgR concentration was found (p less than .05) in the late luteal phase. The results indicate that tumor ER and PgR values change during the menstrual cycle, probably in response to endogenous hormonal fluctuations, and this may account for some vicissitudes in establishing hormone dependence.