The study managed to identify 16 genes that were related to cancer recurrence that belonged to either of the following biological processes: proliferation (such as Ki-67 and cyclin B1), estrogen receptor (including genes such as ER and PR), HER2 (including HER2 and GRB7), and cell invasion (including genes like Stromelysin 3 and Cathepsin L2) [85]. Here, PGR is linked to cancer.