Ovarian cancer is the third most common malignancy in this part of the world, and its incidence is on the rise especially in young age women [
5]. A subset of high-grade serous carcinomas is associated with BRCA mutations. Whether this rising incidence of ovarian carcinoma in this region is linked to BRCA mutations is yet to be fully understood as BRCA mutations are thought to be prevalent in women with breast cancers in this region [
6]. Frozen section evaluation of ovarian tumors is a very useful approach to individualize surgical intervention and conserve fertility when needed and to avoid overtreatment.
The accuracy of the frozen section for ovarian tumors varies among different institutions. Subbian et al. in a study involving 135 cases of ovarian tumors found an overall accuracy of 84.2 %. They found the lowest sensitivity for borderline tumors (31.2 %) especially of the mucinous category [
7]. On the other hand, Supraset et al. in a review of 112 cases revealed a sensitivity of 100, 84, and 92 %, respectively, for benign, borderline, and malignant tumors [
8]. In another retrospective review of 282 cases, sensitivities of the frozen section for benign, borderline, and malignant tumors were 97.5, 95.8, and 95.6 %, and corresponding specificities were 97.5, 97.6, and 100 %, respectively. They found the lowest positive predictive value in borderline group (79.3 %), all of them with mucinous type epithelium as described by other authors [
9]. Another oncology center reported an overall accuracy of 91.85 %. The relative sensitivities were 99.2, 88.46, and 82.95 %, respectively, for benign, borderline, and malignant tumors. There were 18 false negative diagnoses; most of them belonged to the borderline group [
10]. A few authors specifically focused on borderline ovarian tumors. Gultekin et al. evaluated 82 cases of borderline ovarian tumors, 42.7 % of which were of mucinous histology. The concordance with final diagnosis was found in 69.5 % cases. The rates of over-diagnosis and under-diagnosis were 1.2 and 29.3 %, respectively. They proposed that tumor size, presence of solid component, and preoperative CA 125 levels may affect the diagnosis [
11]. Pongsuvareeyakul et al. found a sensitivity of the frozen section for borderline mucinous tumors to be 67.2 % [
12].
Diagnosis of germ cell tumors and sex cord stromal tumors is sometimes difficult on the frozen section as they can mimic surface epithelial tumors. In our study, there were 20 cases of germ cell tumors, all which were mature teratomas and 8 cases of sex cord stromal tumors (4 cases each of granulosa cell tumor and fibro-thecoma). Adult granulosa cell tumors are considered as low-grade malignancy, and initial surgical management depends on the stage of the disease. All of 4 cases in our study were limited to the ovary at initial diagnosis, and there was no evidence of recurrence on follow-up.
The main limitation of the frozen section lies in the accurate diagnosis of borderline ovarian tumors especially of the mucinous category. In a larger retrospective review of 622 ovarian tumors, 52 cases were rendered borderline on frozen section. Terms like at least borderline were also used. Out of these 52 cases, concordance with final diagnosis was seen in 37 cases with an accuracy of 71.15 %. Under-diagnosis occurred in 12 cases and over-diagnosis in 3 cases [
13]. Under-diagnosis in case of borderline ovarian tumors usually occurs as a result of under-sampling. As WHO criteria for the diagnosis of borderline mucinous tumors is quantitative (>10 % of tumors examined showing atypical proliferative features in the absence of frank invasion), it can be misinterpreted in limited sections available on the frozen section. The incidence of over-diagnosis is rare with some examples showing tangential cutting leading to false impression of invasion. In our study, there were two cases in which under-diagnosis was rendered. One of them was of mucinous borderline tumor which was labeled as benign on the frozen section. On further sampling of the tumor after formalin fixation, it turned out to be borderline with >10 % tumor showing epithelial proliferation with nuclear atypia and mitotic activity meeting the criteria of borderline malignancy. The other case was diagnosed as borderline serous tumor on the frozen section due to atypical epithelial proliferation. On final histology, focal areas of invasion were noted occupying >3 mm area and therefore the diagnosis was changed to serous carcinoma. This highlights the importance of sampling for ovarian tumors especially for those of benign and borderline category. Both our cases with disagreements on final paraffin sections seem to be due to sampling errors. Therefore, we suggest that matriculate sampling is needed in ovarian tumors specifically from areas where wall appears thick or there is evidence of solid growth.