They also reported an increase in NK cells containing the Fas early activation molecule (i.e., CD69+ CD56+ NK cells) in the peritoneal fluid of subjects with early (66.8 ± 16.5% vs. 43.3 ± 13.7%, p < 0.01) and advanced (74.2% ± 7.9% vs. 43.3% ± 13.7%, p < 0.01) endometriosis [11]. This evidence concerns the gene FAS and endometriosis.