## 3 Results
### Characteristics of Studies  
Data of the four studies included are summarized in Table 1. These papers were published between January 2021 and October 2022 and reported the data of 2439 women with ages ranging from 11 to 85 years old. The mean prevalence of ovarian cancer was 30.6% (19.0-48.7%). All the studies were retrospective and in all studies the ultrasound was performed by a selection of proficient experts and the reference standard was the histology obtained after surgery.  
Altogether, there was a total of 2541 adnexal masses, where 1797 were benign, 71 borderline and 673 were malignant masses. Nevertheless, one article did not specify such data for any subgroup [40], and only one specified the number of borderline tumors [43]. For statistical analysis, borderline and malignant tumors were grouped together.  
Concerning [PERSON] et al. [40] and [PERSON] et al. [42], two DL models were evaluated. In order to calculate pooled values, we chose the model with better sensitivity and specificity results.  
In [PERSON] et al.'s study [40], the total number of cases was 634 (325 benign cases, 55 borderline, 254 malignant) with a total of 3077 images. In the training dataset there were 508 cases (314 benign and 194 malignant cases). In the validation dataset there were 100 cases (60 benign and 40 malignant cases). Whereas, in the test set there were 150 cases (75 benign and 75 malignant cases).  
Figure 1: Flowchart showing the study selection process. * From January 2000 to October 2023.  
In [PERSON] et al.'s study [42], the total number of cases was 422 (304 benign cases and 118 malignant ones) with a total of 2113 images. In the training dataset there was 296 cases (213 benign and 83 malignant cases) with a total of 1493 images. In the validation dataset there were 41 cases (30 benign and 11 malignant cases) with a total of 189 images. In the test dataset there was a total of 85 cases (61 benign, 24 malignant) with a total 431 images.  
In [PERSON] et al.'s article [43], the total number of cases for internal validation was 460 with a total of 1217 images. There was a total of 377 images of 134 benign cases, a total of 219 images of 56 malignant cases and 57 images of 15 borderline cases. Regarding external validation, which was formed by two different groups, there was in group 1 a total of 198 cases, with a total of 490 images, 134 images of 43 patients with cancer, 27 images of 8 borderline cases and 151 images of 51 benign masses. In group 2, the total number was 264 (a total of 761 images, 97 images of 25 patients with cancer, 30 images of 8 borderline cases and 401 images of 126 benign masses).  
In [PERSON] et al.'s study [44], the total number of cases for internal validation was 868 (3031 images for 266 cases of malignant adnexal masses, and 5385 images of 602 cases of benign adnexal masses). Regarding external validation, two groups were formed with different patients; in external validation 1, the number of cases was 335 (486 images of 67 patients with cancer, and 933 images of 268 benign masses). In external validation 2, the total number was 889 cases (1253 images in the malignant group with 166 cases, and 5257 images from 723 benign cases). In our meta-analysis, we decided to combine the data from both external validation groups to simplify the statistical analysis, where the performances of the model and the experts were compared.  
This information is summarized in Table 2.