PGR and angiomyolipoma: An immunohistochemistry study found progesterone receptor (PR) and estrogen receptor (ER) immunoreactivity in the smooth muscle component of renal angiomyolipomas (100 and 83%) from 12 LAM patients (57), and prevalence of PR expression over ER was confirmed in a large series of pulmonary LAM cases (58); in in vitro studies, ER-α and ER-β expression was observed in cultured angiomyolipoma cells derived from LAM patients (59).