Detection of endometrial pinopodes by light microscopy.

Objective: To study the value of light microscopy (LM) in the assessment of endometrial pinopodes.

Design: Comparative histologic study.

Setting: Outpatient infertility clinic in an academic teaching institution.

Patient(s): Eighteen oocyte donors undergoing controlled ovarian hyperstimulation.

Intervention(s): Endometrial biopsies on days 14-24 of the cycle.

Main Outcome Measure(s): Assessment of pinopodes by scanning electron microscopy (SEM) and of endometrial surface projections by LM.

Result(s): The luminal surface was identified by LM in 36 of 38 endometrial specimens obtained. Although apical projections could be recognized in all, they were few, moderate, and abundant in 20, 12, and 4 cases, respectively. Pinopodes were detected by SEM in all 4 samples with abundant projections, but in only 14 of 32 samples with lesser quantities of these surface features. No predictive value could be ascribed to apical projections viewed by LM for the developmental stage of pinopodes as defined by SEM.

Conclusion(s): The LM of routine endometrial specimens can serve as a preliminary tool in the evaluation of surface morphology. Although abundant apical projections by LM are compatible with the presence of pinopodes by SEM, the latter modality remains as the definitive method in cases with few or moderate projections and for the evaluation of the stage of pinopode development.