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Arias-Stella phenomenon

Synonym: Arias-Stella effect, Arias-Stella reaction.

Focal, unusual, decidual changes in endometrial epithelium, consisting of intraluminal budding, and nuclear enlargement and hyperchromatism with cytoplasmic swelling and vacuolation; may be associated with ectopic or uterine pregnancy. 


A: Extensive and confluent endocervical gland involvement by the Arias-Stella effect. B: Partial gland involvement by the Arias-Stella effect is characteristic.
From:   Nucci: Am J Surg Pathol, Volume 28(5).May 2004.608-612