Arias-Stella reaction
# 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.

## Significance

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

## Diagnosis

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:

* Minimal atypia.
* Early secretory pattern.
* Secretory or hypersecretory pattern.
* Regenerative, proliferative or nonsecretory pattern.
* Monstrous cell pattern.

## History

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

