In some cases, your nipple may retract (pull inwards) during a bout with mammary duct ectasia. (verywell.com)
I personally know of some moms who were on the verge of mastitis due to blocked mammary ducts but were rescued by great suction and efficiency of Spectra S1. (electricbreastpumpwomen.com)
«Breast cancer researchers track changes in normal mammary duct cells leading to disease.» (sciencedaily.com)