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Confluence of predecidua between multiple arterioles is the hallmark of day 24 endometrium.

Day 24 endometrium demonstrates confluence of predecidua between multiple arterioles. Note that the thin layer of predecidua has not yet formed underneath the surface epithelium, which is a feature of day 25 endometrium.


In late secretory endometrium (day 23-27), the presence of predecidualization and its location is key to dating.


1 Mazur MT, Kurman RJ. Diagnosis of Endometrial Biopsies and Curettings. New York, NY: Springer; 2005: 12-19.

2 Nucci MR, Oliva Esther. Gynecologic Pathology: Foundations in Diagnostic Pathology. Philadelphia, PA: Elsevier: 2009: 202-4.

Last updated: 2010-10-21
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