Objectives We aimed to assess the following morphological characteristics of serous and mucinous borderline ovarian tumors (BOT) as stratified by Kurman: microinvasion, non-invasive implants or/and invasive implants, linfonodal invasion, microinvasive carcinoma, intraepithelial carcinoma and mural nodules. Once they were determined, we assessed the relationship between microinvasion and clinical characteristics and the other morphological features addressed above.

Methods 74 women with serous and mucinous BOT were selected. Two experienced pathologists following Kurman criteria determined morphological characteristics. Disease-free was calculated and compared to presence of microinvasion as well as clinicopathological features. We also calculated the relation between the presence of microinvasion and all other morphological features.

Results A mean follow-up period of 57.6 months was achieved where 48% of patients had serous BOT and 52% had mucinous tumors. Microinvasion was the most frequent morphological feature detected in both subtypes. The patients with microinvasion had higher CA125 levels (172.6 + 255.9U/mL vs. 78.6 + 114.5U/mL; p=0.04) than their counterparts. In addition, in patients with microinvasion, the serous subtype was more prevalent than in those patients without microinvasion (65.4% vs. 38.2%; p=0.02). Microinvasion was not associated with any other clinical characteristic nor the presence of any other morphological feature.

Conclusions Microinvasion is one of the most controversial BOT feature considering management, prognosis and follow-up. In our study, microinvasion was significantly associated with higher Ca125 levels and serous subtype. In ovarian cancer, Ca125 levels are associated with disease extent. Therefore, higher Ca125 levels in women with microinvasion may indicate tumors affecting more agressively the celomic epithelium.