Arias-Stella reaction in nonpregnant women: a clinicopathologic study of nine cases.

The Arias-Stella reaction (ASR) is a common and universally recognized feature of gestational endometrium. That identical cytologic changes may, on occasion, occur outside the endometrium or in nonpregnant women is not as well documented. This report describes the clinical and pathologic findings in nine nonpregnant women whose endometria demonstrated ASR. The defining characteristics of ASR, associated pathologic changes, and differential diagnosis are discussed. All of these women were peri- or postmenopausal, and eight of nine had received exogenous hormones, most (n = 7), progestational agents. ASR did not persist in the four patients who underwent subsequent endometrial examination. None of these patients developed adenocarcinoma, although follow-up was short. ASR is an unusual response to hormonal therapy in nonpregnant patients. It is important to recognize the phenomenon in this setting and not overinterpret the characteristic cytologic atypia as adenocarcinoma.