MUC1 and breast cancer: Since a substantial proportion of patients who undergo ovarian tissue cryopreservation is diagnosed with breast cancer [10–12], we tested a panel of cell-surface markers known to be expressed by breast cancer cells, including E-cadherin [13], epithelial membrane antigen (EMA, also known as MUC1) [14, 15], human epidermal growth factor receptor type 2 (Her2/neu) [16, 17], carcinoembryonic antigen (CEA) [18], αvβ6 integrin [19] and epithelial cell adhesion molecule (EpCAM) [20–22].