An update regarding the effects of hormones on the endometrium: practical considerations for the surgical pathologist

The endometrium displays a unique physiology characterized by its cyclical response to steroid hormones, which results in morphological changes that contribute to a pathologist's interpretation of proper endometrial function. Distinctive changes are also observed during times of physiological hormonal shifts (such as during pregnancy), pathological hormonal imbalances (such as certain functioning ovarian tumours) and iatrogenic hormonal imbalances (such as hormone therapy). The ubiquity of these states, particularly in conjunction with the widespread use of oral contraceptives, hormone replacement therapy, and intrauterine devices, requires that the pathologist be familiar with both the complete patient history and the histologic patterns specific to each entity in order to obtain an accurate and practical diagnosis for the clinician. Furthermore, some endometrial changes may mimic more worrisome lesions, and vigilance is necessary to accurately distinguish among these histologic patterns when evaluating endometrial samples.