In our study, high expression levels of CD90 were found in all AF samples, which were strongly positive for the embryonic stem cell characteristic markers (Oct-4, Sox-2, Rex-1, and Nanog) that are associated with the maintenance of the undifferentiated state and the pluripotency as was demonstrated previously [13, 16, 24, 25]. The gene discussed is SOX2; the disease is atrial fibrillation.