Polymorphonuclear leukocytes in the endometrium during the normal menstrual cycle

We investigated the presence of polymorphonuclear leukocytes (PMNs) in normal endometrium. Hematoxylin and eosin stained slides of 100 endometrial curettage and biopsy specimens were reviewed for dating and presence of PMNs. Polymorphonuclear leukocytes were quantitated by chloroacetate esterase (CAE) stains. Polymorphonuclear leukocytes were present in large numbers in areas of tissue degradation (day 28 and menstrual phase endometrium) and were found only in small numbers in intact tissue throughout the cycle. The CAE and H&E stains showed minimal difference in ability to detect PMNs. Polymorphonuclear leukocytes could be easily discriminated from endometrial granulocytes, which did not stain with CAE.