Elevated FAP expression (H-score ≥10) was detectable in 84% of endometriosis cases in endometriomas of the ovary, superficial peritoneal lesions, deep infiltrating endometriosis, and extra-abdominal lesions (Fig. 1A, C, D, and F) and only 4% of extralesional controls. The gene discussed is FAP; the disease is endometriosis.