Microscopic description and IHC:
The dilation and curettage specimen shows gestational endometrium with scattered hypercellular endometrial glands. The cells in the glands are increased in size, protrude into the lumen, have eosinophilic and vacuolated cytoplasm, and enlarged, irregular nuclei. The nuclear to cytoplasmic ratio is preserved and mitotic figures are inconspicuous.
Discussion:
Arias-Stella reaction is a fairly common finding in reproductive –aged women due to hormonal changes from pregnancy, oral contraceptives, or hormone replacement therapy. Although the glands are hypercellular and enlarged they do not have the same architectural complexity and increased stroma to gland ratio as complex atypical hyperplasia. Clear cell adenocarcinoma of the uterus does have a similar hobnail appearance, however, the cells show more irregularity ,prominent nucleoli, and increased mitotic figures.
Syncytiotrophoblasts and cytotrophoblasts are not present, as would be seen in choriocarcinoma. Additionally, the HCG would be much higher. Placental villi, implantation site, and other fetal parts are not present confirming the suspicion of an ectopic pregnancy.