Distribution of Aldehyde Dehydrogenase 1-positive Stem Cells in Benign Mammary Tissue from Women with and Without Breast Cancer

Aims: Aldehyde dehydrogenase 1 (ALDH1) in female breast tissue has been linked to stem cells, but little is known about the benign cellular organization in situ. We investigated the distribution of ALDH1-immunoreactive (ALDH1+) cells in histomorphologically benign breast tissue from 28 women with or without breast cancer.

Methods And Results: ALDH1+ cells were detected in benign tissue of women aged 20-72 years, located most commonly at the luminal and intermediate ductular levels and in the stroma. ALDH1+ cell populations and Ki67+ cell populations were present in separate ductules, both cell types rarely showing epithelial differentiation. ALDH1+ cells were non-reactive to Ki67 and oestrogen receptor. Stromal round/oval ALDH1+ non-leukocyte cells in both age groups expressed contractile protein. There was a lower concentration of luminal and intermediate ductular ALDH1+ cells in postmenopausal women than in premenopausal women, and in cancer patients than in non-cancer patients, and a higher concentration in women receiving exogenous hormones.

Conclusions: This study provides further evidence for the stem cell character of ALDH1+ cells, here in benign breast tissue of cancer and non-cancer patients throughout non-lactating adult life, and contributes evidence of benign stromal ALDH1+ cells. The distribution of ductular ALDH1+ stem cells appears to be influenced by hormonal status.