Haptoglobin expression by shed endometrial tissue fragments found in peritoneal fluid

Haptoglobin expression by retrogradely shed endometrial tissues in peritoneal fluid supports a mechanism whereby these purported precursors of endometriotic lesions escape immune destruction. Low recovery of histologically confirmed endometrial tissue fragments from peritoneal fluid reveals the potential difficulties for using these tissues for studies modeling the pathogenesis of endometriosis.