Local mononuclear cell infiltrates in infertile patients with endometrial macropolyps versus micropolyps

STUDY QUESTION: Is the endometrial mononuclear cell population in infertile patients altered in subjects with classical endometrial polyps (macropolyps) versus endometrial micropolyps that are hysteroscopically recognized as small uterine cavity protrusions? SUMMARY ANSWER: Macropolypoid endometrium had a low density of pan-leukocytes, pan-T cells and natural killer (NK) cells, whereas micropolypoid endometrium was characterized by high density of B cells and plasmacytes, along with a low density of NK cells. WHAT IS KNOWN ALREADY: Endometrial micropolyps co-exist at a high rate with chronic endometritis, which is an unusual plasmacyte infiltration within the endometrial stromal compartment. STUDY DESIGN: Prospective cross-sectional study. From July 2009 to June 2011, hysteroscopy was performed for infertile women who had been suspected for endometrial macropolyps and who had repeated in vitro fertilization-embryo transfer failure over three or more cycles. Endometrial biopsy samples were obtained from the patients with macropolyps or micropolyps during the proliferative phase. Of 137 patients assessed, 30 were diagnosed with endometrial macropolyps and 34 were diagnosed with endometrial micropolyps. After the exclusion of the cases with heavy uterine bleeding, potential neoplasms, submucosal uterine fibroids, uterine septa, and/or intrauterine adhesion, 23 patients with macropolypoid endometrium; 25 patients with micropolypoid endometrium and 27 patients with non-polypoid endometrium were enrolled in the study. Endometrial macropolyps were surgically removed, whereas chronic endometritis was treated with antibiotics. The patients were followed up until December 2011. PARTICIPANTS/MATERIALS, SETTING, METHODS: The paraformaldehyde-fixed paraffin-embedded endometrial sections were immunostained with monoclonal antibodies against the specific markers of pan-leukocytes (CD45), pan-T cells (CD3), Th cells (CD4), Tc cells (CD8), B cells (CD20), plasmacytes (CD138), NK cells (CD56) and macrophages (CD68). The immunoreactive cells were enumerated in at least 20 non-overlapping stromal areas. MAIN RESULTS AND THE ROLE OF CHANCE: Compared with the non-polypoid endometrium, macropolypoid endometrium contained a lower density of pan-leukocytes, pan-T cells and NK cells, whereas micropolypoid endometrium had a higher density of pan-leukocytes and B cells, along with a lower density of NK cells. Following the treatments, 10 patients with macropolypoid endometrium, 11 patients with micropolypoid endometrium and 10 patients with non-polypoid endometrium conceived. LIMITATIONS, REASONS FOR CAUTION: One potential bias is immunohistochemical enumeration for leukocyte density was conducted by one examiner. The limitation of this study is that the results relied on endometrial biopsy specimens, of which immunological conditions may not always represent those in the whole endometrium. WIDER IMPLICATIONS OF THE FINDINGS: There may be some ethnic or racial variances in the composition of the endometrial mononuclear cell subsets of infertile women.