Borderline ovarian tumor frozen section diagnoses with features suspicious of invasive cancer: a retrospective study.

Background: A frozen section diagnosis of a borderline ovarian tumor with suspicious features of invasive carcinoma ("at least borderline" or synonymous descriptions) presents us with the dilemma of whether or not to perform a full ovarian cancer staging procedure. Quantification of this dilemma may help us with the issue of this clinical decision. The present study assessed and compared both the prevalence of straightforward borderline and "at least borderline" frozen section diagnoses and the proportion of these women with a final histopathological diagnosis of invasive carcinoma, with a special interest in histologic subtypes.

Methods: A retrospective cohort study was performed in three hospitals in The Netherlands. All women that underwent ovarian surgery with perioperative frozen section evaluation in one of these hospitals between January 2007 and July 2018 were identified and included in case of a borderline or "at least borderline" frozen section diagnosis and a borderline ovarian tumor or invasive carcinoma as a final diagnosis.

Results: A total of 223 women were included, of which 41 women (18.4%) were diagnosed with "at least borderline" at frozen section. Thirteen of forty-one women (31.7%) following "at least borderline" frozen section diagnosis and 14 of 182 women (7.7%) following a straightforward borderline frozen section diagnosis were diagnosed with invasive carcinoma at paraffin section evaluation (p < 0.001). When compared to straightforward borderline frozen section diagnoses, the proportion of women diagnosed with invasive carcinoma increased from 3.1 to 35.7% for serous tumors (p = 0.001), 10.0 to 21.7% for mucinous tumors (p = 0.129) and 50.0 to 75.0% (p = 0.452) in case of other histologic subtypes following an "at least borderline" frozen section diagnosis.

Conclusions: Overall, when compared to women with a decisive borderline frozen section diagnosis, women diagnosed with "at least borderline" frozen section diagnoses were found to have a higher chance of carcinoma upon final diagnosis (7.7% vs 31.7%). Especially in the serous subtype, full staging during initial surgery might be considered after preoperative consent to prevent a second surgical procedure or chemotherapy in unstaged women. Further studies are needed to evaluate whether additional sampling in case of an "at least borderline" diagnosis may decrease the risk of surgical over-treatment.