To investigate the differences in ultrasound features according to the ovarian-adnexal reporting and data system (O-RADS) and clinical characteristics among ovarian serous tumors of different pathological types, and to analyze the application value of ultrasonic O-RADS characteristics and clinical characteristics in the diagnosis of ovarian serous tumors of different pathological types.

A total of 57 patients diagnosed with ovarian serous tumors, containing 76 adnexal masses, by pathological examination at The Second Affiliated Hospital of Zhejiang University School of Medicine from January 2021 to June 2022 were retrospectively analyzed. The clinical data and ultrasound images of the patients were recorded. The patients were divided into benign serous tumor group (n=20), serous borderline tumor group (n=16), and malignant serous tumor (serous carcinoma) group (n=21) according to the histopathological type. One-way analysis of variance was used to compare the differences in age, body mass index, and maximum tumor diameter among patients of the three groups. The rank sum test was used to compare the CA125 level, blood flow, number of papillary projections, and O-RADS characteristics between any two groups of the three groups. The chi-square test was used to analyze the differences in chief complaints among patients of the three groups. The chi-square test with Bonferroni correction was used to compare peritoneal thickening/nodules and (or) abdominal effusion, lesion location, composition, and complete separation between any two groups of the three groups. Receiver operating characteristic curve (ROC) analysis was used to assess the diagnostic performance of CA125 and O-RADS classification for ovarian serous tumors.

In terms of clinical characteristics, the percentage of bilateral lesions in the benign, borderline, and malignant tumor groups was 15.0% (3/20) vs 18.7% (3/16) vs 61.9% (13/21), the percentage of patients accompanied by peritoneal thickening/nodules and (or) abdominal effusion was 0% (0/20) vs 0% (0/16) vs 57.1% (12/21), and the percentage of patients with high serum CA125 levels was 15.8 (7.8, 21.7) U/ml vs 43.3 (29.4, 105.6) U/ml vs 1229.2 (142.9, 2222.7) U/ml; the differences among the three groups were statistically significant (χ²=12.271, P=0.003; χ²=18.321, P<0.001; H=38.393, P<0.001). The cut-off value of serum CA125 level for diagnosing malignant serous tumors was 293.0 U/ml (area under the curve [AUC]=0.917), with a sensitivity and specificity of 71.43% and 100%, respectively. In terms of ultrasound features, the percentage of multilocular cyst lesions with solid component(s) in the benign, borderline, and malignant tumors groups was 13.1% (3/23) vs 21.0% (4/19) vs 91.2% (31/34), the percentage of lesions with blood flow score ≥2 was 0% (0/23) vs 68.4% (13/19) vs 82.4% (28/34), the percentage of cystic lesions with the number of papillary projections >3 was 0% (0/23) vs 68.4% (13/19) vs 8.7% (2/23), and the percentage of multilocular cystic lesions was 34.8% (8/23) vs 21.1% (4/19) vs 87.0% (20/23); the differences were statistically significant among the three groups (χ²=89.998, P<0.001; H=35.407, P<0.001; H=26.210, P<0.001; χ²=19.477, P<0.001). The sensitivity and specificity of O-RADS 4-5 in diagnosing borderline or malignant serous tumors were 92.45% and 82.61%, respectively.

There are different ultrasonic O-RADS characteristics and clinical characteristics in ovarian serous tumors of different pathological types. They can be effectively distinguished by the clinical characteristics (CA125 level and lesion location) and ultrasonic O-RADS characteristics (composition, complete separation, blood flow, and number of papillary projections ) of the patients.