Endometrial dating based on histomorphology
In contrast, secretory-phase endometrium often demonstrates subtle changes and, in many cases, combinations of morphologic changes, resulting in most instances in errors of 4–5 days.
The pathologist can improve this to 2–3 days, however, by acquiring expertise in endometrial dating (all cases of normal endometria are to be dated regardless of reasons for sampling), and by basing the dating on those endometrial morphologic alterations that represent the most advanced phase of the menstrual cycle.
Steroid hormone control of endometrial, epithelial, stromal, and presumably endothelial cells is mediated by estrogen receptors and progesterone receptors. They have high affinity to bind estradiol and progesterone, respectively.
These steroid receptors are specific proteins concentrated exclusively in the nuclei of both endometrial epithelial and stromal cells, as well as the endothelial cells of stromal capillaries. This chapter contains a review of the technical procedures for handling endometrial tissues and a discussion of the morphologic aspects of the endometrium, focusing on the interpretation and understanding of the physiomorphology of the endometrial cycle.
For example, if an endometrial biopsy contains changes consistent with postovulatory days (POD) 2, 3 and 4, the pathologist should report the diagnosis as ' POD 4 or 18-day secretory endometrium'.
Endometrial biopsies are not to be taken at the onset of bleeding in the following two conditions: if luteal phase defect (LPD) is suspected clinically and is desired to be confirmed histologically, when the biopsy should be taken between POD 7 (21st) and POD 9 (23rd) cycle days to demonstrate a 3–4 day delay in endometrial maturation; or if there are asynchrony of gland/stromal development and dissimilar maturation in different regions of the endometrial specimen.
In the most common terminology for dating the endometrial biopsy, day 1 is used as the first day of bleeding, and this is used in Fig. Endometrial cycle length is often described as an idealised 28 days in duration, but this may be slightly longer or shorter even in normal women.
These physiologic variations occur in the preovulatory phase, as tight programming of postovulatory events fixes the postovulatory interval at about 14 days.
The final argument in favor of taking samples at the onset of bleeding is that endometrium of the first 2 days of menstruation is relatively easy to recognize histologically.
In premenopausal women with regular menstrual cycles, histological preparations include the upper portion of the functional layer of the endometrium.
This is necessary, for in most instances morphological changes occur in the functionalis as opposed to the basalis layer, and, by inference, provide a clinically useful diagnosis.
Timing The best way to prove or disprove that ovulation has taken place is to take an endometrial sample on cycle day 22 or later, preferably at the onset of uterine bleeding.
By obtaining samples at the time of early uterine bleeding, the pathologist will be able to determine whether the bleeding is caused by the breakdown of postovulatory, secretory endometrium; by focal necrosis of the endometrium associated with anovulation; by other pathologic states; or by hormone administration.