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.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.Method To ensure a good specimen for morphologic interpretation, a biopsy sample should be taken from both the anterior and the posterior endometrium and fixed immediately in 10% buffered formalin.In current practice, the device that is most often used is the Pipelle endometrial aspirator.
According to most investigators, measurements of serum progesterone levels rather than histological dating of the endometrium provide for the best assessment of LPD (see discussion later in this chapter).
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.
In cases of clinical membranous dysmenorrhea, the endometrial biopsy should be taken on cycle days 5–10.
In these instances, the histologic specimens contain large fragments (casts) of endometrium, often with focal Arias-Stella reaction, or star-shaped glands with dense stroma alternating with foci of normal menstrual endometrium.