ESR1 and breast cancer: By multivariate survival analysis, mammary cancer progression (disease-free interval) in feline patients of the present study was independently modulated by Sox2, tumor size, ER and AR, with larger tumor size associated with poor prognosis, as frequently reported in FMCs (19–21, 49–55), AR associated with decreased probabilities of cancer progression (20), and ER expression associated with shortened DFI.