Is there a seasonal variation in oestrogen receptor levels in human breast carcinoma tissues?

The seasonal variation of the incidence of oestrogen receptor-positive mammary carcinomas was investigated in 556 postmenopausal women. In addition, the seasonal variation in receptor concentration in 289 oestrogen receptor-positive breast carcinomas was studied. Neither the proportion of oestrogen receptor-positive carcinomas, nor the concentration of the receptor in the tumours, varied significantly during the year.