Endometrial Eosinophilic Syncytial Change Related to Breakdown: Immunohistochemical Evidence Suggests a Regressive Process

Abstract

Eosinophilic syncytial change (ESC), also known as papillary syncytial change, occurs in association with endometrial breakdown and bleeding, especially in nonphysiological conditions. When prominent, this morphological alteration yields a pattern of eosinophilic epithelial cells, often in pseudopapillary arrangements that can mimic cellular changes seen in metaplastic and atypical endometrium. To determine if ESC represents a proliferative, regenerative process or a degenerative, retrogressive alteration, we assessed whether the cells of ESC were actively growing. Our methodology involved a retrospective immunohistochemical study on endometrial biopsies with proliferation markers Ki-67 (MIB-1 antibody) and phosphohistone H3 Ser 28 (pHH3) in 15 cases of multifocal ESC associated with benign endometrium, 5 cases of atypical hyperplasia, and 7 cases of endometrial carcinoma. The Ki-67 proliferative index and the pHH3 mitotic index were calculated per 100 cells for each case. On immunohistochemical analysis, the Ki-67 labeling index was 1.3% for cases of ESC (mean age, 53 yr), 15.8% in atypical hyperplasia (mean age, 51.6 yr), and 42.6% in endometrial carcinoma (mean age, 68.1 yr). In the endometrial cancers, the Ki-67 proliferative index was 10.6% for FIGO grade 1 tumors (n=3), 27.6% for grade 2 tumor (n=1), and 79.6% for serous carcinoma (n=3). The mitotic index calculated from pHH3 immunostaining was zero in all cases of ESC, whereas it was 2.3% in atypical hyperplasia and 4.8% in endometrial carcinomas (2.4% for grade 1, 3% for grade 2, and 7.8% for serous). Our results indicate that ESC is a regressive change. Furthermore, when there is a question of whether eosinophilic endometrial epithelium represents this change, a combination of Ki-67 and pHH3 immunostains can be helpful in distinguishing this entity from more significant processes including carcinoma.