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 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.
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.
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.Also, during the period of bleeding, both the external os and the isthmus (lower uterine segment) are widened, facilitating penetration of the biopsy forceps into the endometrial cavity.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.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.Because of the stabilizing effect of progesterone on lysosomal enzymes and prostaglandins, menstrual breakdown may be delayed, prolonged, and extensive.
The major morphologic criteria useful for dating the endometrium throughout the cycle are presented in Fig. In routine dating, the pathologist should avoid bias by evaluating the histologic section before reading the clinical information.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.Such a condition, also called irregular shedding, is presumably associated with a persistent corpus luteum from a recent or remote intrauterine or ectopic pregnancy and with relatively increased blood progesterone levels.These physiologic variations occur in the preovulatory phase, as tight programming of postovulatory events fixes the postovulatory interval at about 14 days.It is not necessary to date the endometrium during the proliferative phase.In current practice, the device that is most often used is the Pipelle endometrial aspirator.