One study using dual-colour flow cytometry showed that CD20+ B cells were significantly more abundant in 20 endometriosis samples compared with 15 controls; 10% of the lymphocytes (identified by CD45+CD14−) were CD20+ endometrial B cells in controls, 12% in eutopic endometrium and 17% in ectopic endometrium from patients with endometriosis. This evidence concerns the gene MS4A1 and endometriosis.