The tubal stroma beneath the epithelium shows increased eosinophilic cytoplasm indicative of decidual change.

The decidualized cells are better visualized on higher power -- note their polygonal shape and abundant eosinophilic cytoplasm.

The fallopian tube stroma undergoes decidualization in 5-12% of intrauterine pregnancies and up to 80% of tubal pregnancies.1 Microscopically, one sees polygonal cells with abundant pink cytoplasm with prominent cell borders. The nuclei are uniform, bland and ovoid/round.

Seen most often in those undergoing tubal ligation after delivery and rarely, and in women receiving progestin therapy.

• Endometrium : Arias-Stella Reaction