PGR and neoplasm: Positivity to Sox2 has been associated with a larger tumor size (11–15), presence of lymph node metastasis (8, 9, 11, 15), a higher histological grade (8, 9, 14–16), a higher Ki-67 proliferation index (13, 14, 16), and negativity to Estrogen Receptor (ER) and Progesterone Receptor (PR) (12, 14).