Pituitary tumor cells from AF males exhibited stem‐like cell properties and showed elevated expression of stem cell regulatory genes and proteins (SOX‐2, OCT‐4, KLF4, SNAIL‐1, and Nestin), tumor aggressiveness markers (MMP‐9, CD44, CD34, PTTG, FGFR4, Ki‐67, N‐Cadherin), and prolactin compared to those from AD and PF controls. The gene discussed is MMP9; the disease is atrial fibrillation.