The 23-gene classifier, RecurIndex®, was initially developed using the microarray platform technology to evaluate the prognosis capability of the test in classifying Asian breast cancer patients into two categories, high and low risks of distant recurrence. This 23-gene genomic test comprises 20 breast cancer recurrence-related genes with three housekeeping genes and six clinical factors (the age at first diagnosis, the nodal stage, the tumor grading, the tumor size, the estrogen receptor (ER) status, and the lymphovascular invasion (LVI) status)