Arias-Stella reaction

Arias-Stella reaction, also Arias-Stella phenomenon, is a benign change in the endometrium associated with the presence of chorionic tissue.

[1] Arias-Stella reaction is due to progesterone primarily.

Cytologically, it resembles a malignancy and, historically, it was misdiagnosed as endometrial cancer.

It is characterized by nuclear enlargement and may also have any of the following: an irregular nuclear membrane, granular chromatin, centronuclear vacuolization, and pseudonuclear inclusions.

[1] Five subtypes are recognized:[1] It was first described by Javier Arias Stella, a Peruvian pathologist, in 1954.