In fact, anomalous susceptibility of endometrial tissue to apoptosis may deeply contribute to the development of implants3; in particular, it has been reported that expressions of FAS and its ligand may be decreased in eutopic and ectopic endometria of women with endometriosis.4 In contrast, higher levels of proapoptotic proteins, such as FAS ligand, in the peritoneal fluid of women with endometriosis may contribute to an increased apoptosis of immune cells, leading to decreased scavenger activity in the peritoneal cavity and, thus, less immune clearance.5 This evidence concerns the gene FAS and endometriosis.