endometrial hyperplasia without atypia

Definition: Endometrial hyperplasia without atypia is a proliferation of endometrial glands of irregular size and shape without significant cytological atypia.

Simple hyperplasia without atypia is characterized by cystically dilated glands of various shapes and sizes. There is mild increase in gland-to-stroma ratio. Progression to adenocarcinoma occurs only in about 1% of cases.

Endometrial hyperplasia is the result of excessive estrogenic stimulation of the endometrium. Associated conditions include obesity, polycystic ovary disease (including Stein-Leventhal syndrome), functioning granulosa cell tumors of ovary, and exogenous estrogens etc.

Microscopy

 By definition, there is no cytologic atypia and no significant complexity (glandular confluence with loss of individual glandular contours, cribriform or microacinar architecture)

 Gland to stroma ratio is greater than 1:1 (glands occupy more than 50% of the surface area);

• these areas of "gland crowding" still contain small amounts of stroma in between glands, and the individual glandular contours can be easily distinguished
• Glands are usually round or elongated; however, shape and size irregularity are common including cystic dilation

 Lining epithelium usually displays proliferative-type morphology with pseudostratified or mildly stratified columnar cells containing elongated cigar shaped nuclei
 Metaplastic change (tubal, mucinous, squamous, secretory) can be seen
 Cellular stroma with variable mitotic activity, uniformly distributed blood vessels

Images

 http://www.webpathology.com/image.asp?n=2&Case;=568

See also

 endometrial hyperplasia

• complex endometrial hyperplasia
• endometrial intraepithelial neoplasia (EIN) / atypical hyperplasia
• progestin therapy related changes