LAUSR

Background Ovarian “seromucinous carcinoma” has been recently removed in 2020 5 th Edition of WHO classification of Female Genital Tumors and is considered as a subtype of endometrioid carcinoma with mucinous differentiation, while “seromucinous borderline tumor” remains and exists as a distinct entity. Both diseases may be considered as no more same lineage. However, ovarian seromucinous borderline tumor (SMBT) is also one of the endometriosis-related neoplasm of ovary similar to endometrioid tumor, featuring that about 50% of ovarian SMBTs combine endometriosis. The present study was aimed to investigate whether the ovarian SMBTs are different in clinical features and molecular patterns, according to the presence of combined endometriosis. Results There were no statistical differences in clinical findings between two groups. There was also no significant difference in pregnancy outcomes and recurrence between two groups. In immunohistochemical patterns, there was a statistically significant difference in PAX2 and PAX8 expression between in ovarian SMBT with or without endometriosis ( P  = 0.016, P  < 0.001). Only a few cases of ovarian SMBT with endometriosis showed expression of PAX2 and conversely, most of the cases showed expression of PAX8. PR positivity was more prominent in ovarian SMBT with endometriosis than without endometriosis ( P  = 0.018), although there was no difference in positive ER expression. There were no statistical differences in WT1, CK20 and CDX2 expressions between two groups. Conclusions Ovarian SMBT with endometriosis did not clinically differ from that without endometriosis. However, the molecular patterns were different between two groups and ovarian SMBT with endometriosis is close to endometrioid tumor types unlike SMBT without endometriosis. Further, a direct comparison study between seromucinous borderline tumor and endometrioid borderline tumor is needed with a gene profiling study to prove their relationship.