Micropapillary pattern in serous borderline ovarian tumor and the risk of extraovarian localization of low-grade serous carcinoma (‘invasive implants’): A systematic review and meta-analysis

In serous borderline ovarian tumor (SBOT), a micropapillary (MP) pattern has been considered analogous to intraepithelial low-grade serous carcinoma (LGSC). On this account, it is reasonable to hypothesize that MP-SBOT is more likely to be associated with extraovarian LGSC localizations (also referred to as 'invasive implants') compared to conventional SBOT. The aim of this study was to investigate the potential association between a MP pattern and invasive implants in SBOT. Three electronic databases were searched from 2000 (year of publication of histological criteria for MP-SBOT) to 2023 for all studies assessing the presence of invasive implants in conventional SBOT vs MP-SBOT. Exclusion criteria were sample size <20, overlapping patient data, reviews. The association between MP pattern and invasive implants was assessed by using odds ratio (OR), with a significant p-value<0.05. Seven studies with 1766 SBOT were included, out of which 205 (11.5 %) were MP-SBOT, 462 (26 %) had implants and 62 (3.5 %) had invasive implants. A MP pattern was significantly associated with the presence of invasive implants (OR=7.33, 95 % CI 3.61–14.86) (p<0.001), with low heterogeneity among studies (I²=28 %). In conclusion, a MP pattern in SBOT is significantly associated with extraovarian LGSC localization, supporting that it represents intraepithelial LGSC.