Arias-Stella reaction.

OBJECTIVE: Endometrial cytology in nine cases of ectopic pregnancy was examined in order to elucidate the cellular characteristics of the Arias-Stella reaction and decidual change. STUDY DESIGN: The cellular findings of epithelial and stromal cells were compared with histologic findings in each case. Furthermore, the immunocytochemical reactivity of each type of cell cluster-epithelial cells without atypia, epithelial cells with atypia, deep stromal cells and sheetlike stromal cells-to epithelial membrane antigen (EMA) or vimentin was investigated and compared with cytologic findings in smears stained with Papanicolaou stain. RESULTS: The distribution of each type of cell cluster correlated fairly well with the histologic findings on the endometrium. Immunocytochemical examination revealed that EMA expression coincided with cell origin identified by Papanicolaou stain. Epithelial cells with atypia, probably corresponding to the Arias-Stella reaction, frequently showed positive reactivity to antivimentin antibody as well as anti-EMA antibody. Endometrial stromal cells usually indicated negative reactivity to anti-EMA antibody. Deep stromal cells expressed vimentin, but sheetlike stromal cells, thought to be decidual cells, infrequently expressed vimentin. CONCLUSION: The Arias-Stella reaction may be the result of the regenerating and proliferating activity of endometrial glands. It is still controversial whether sheet-like stromal cells are identical to decidual cells.

Toki N, Kawagoe T, Matsuura Y, Sugihara K, Kashimura M, Kashimura Y. Cellular characteristics of Arias-Stella reaction in ectopic pregnancy. Immunocytochemical studies with epithelial membrane antigen and vimentin. Acta Cytol. 1997 Mar-Apr;41(2):285-90.