Arias-Stella reaction

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

Arias-Stella reaction is due to progesterone primarily.

Cytologically, it looks like a malignancy and, historically, it was diagnosed as endometrial cancer.

It is significant only because it can be misdiagnosed as a cancer. It may be seen in a completely normal pregnancy.

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.

Five subtypes are recognized:

It was first described by Javier Arias Stella, a Peruvian pathologist in 1954.

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