TP53 and invasive ductal breast carcinoma: In this model, p53−/− hyperplastic cells are transplanted into the cleared fat pads of pre-pubertal Balb/c mice where they form ductal hyperplasias by 8 weeks post-transplantation, low grade MIN by 12 weeks, and progress to high grade MIN/invasive ductal carcinoma by 16 weeks (14, 16).