Fibroadenomas are the most common benign
breast tumors, occurring mainly in young women. Their responses to the hormonal environment are similar to those of normal breast tissue, which suggests that
steroid receptors may play a role in
tumor development. We evaluated the gene and
protein expression of
progesterone receptors A and B (PRA and PRB) and the
protein expression of
estrogen receptor alpha (ER-alpha) in
fibroadenoma samples, comparing with adjacent normal breast tissue, from 11 premenopausal women.
Progesterone and
estradiol levels were determined. No alterations in the PRs gene and
protein expression and the ER-alpha
protein expression were observed between the follicular and luteal phases, in normal breast versus
fibroadenomas.
Protein levels of PRA and PRB were higher in
fibroadenomas compared to normal breast tissue (P = 0.038 and P = 0.031), while the PRs
mRNA levels were similar in both tissues (P = 0.721 and P = 0.139). There were no differences in ER-alpha
protein expression between normal breast tissue and
fibroadenomas (P = 0.508). The PRA:PRB ratio was similar in the tissues, and also showed a strong correlation in both (r = 0.964, P = 0.0001). Our data suggest a role of PRs in the growth and development of
fibroadenomas, although without alterations of the PRA:PRB ratio in these
tumors. The absence of alterations in ER-alpha
protein levels could be a characteristic behavior of
fibroadenomas, unlike
breast cancer.