The goal of this observational study is to learn whether a blood-based cell-free DNA (cfDNA) methylation assay can help detect ovarian cancer, especially early-stage ovarian cancer, in women undergoing clinical evaluation for ovarian tumors or gynecologic diseases. The main questions it aims to answer are:

How well can this assay distinguish ovarian cancer from benign gynecologic diseases? How accurately can this assay detect early-stage ovarian cancer and other ovarian tumor subtypes?

Researchers will compare the test results from participants with ovarian cancer and participants with benign gynecologic diseases to evaluate the diagnostic performance of the assay.

Participants will:

Provide blood samples for cfDNA methylation testing Allow researchers to collect clinical and pathological information related to their diagnosis Be grouped according to their final clinical or pathological diagnosis for analysis

Inclusion Criteria:

• Female participants.
• Participants with an ovarian/adnexal mass who are planned to undergo, for the first time at the current center, surgery or biopsy/pathologic sampling related to the current lesion, with an expected pathologic diagnosis available as the reference standard.
• Imaging evaluation during screening suggests a unilateral or bilateral, unilocular or multilocular cystic-solid or solid ovarian/adnexal mass requiring differential diagnosis.
• An adequate peripheral blood sample can be collected before the first surgery or before initiation of any systemic anti-tumor treatment for the current ovarian/adnexal mass, and the sample can be processed and stored within the required time according to the unified study procedures.
• Clinical data and postoperative pathologic results are expected to be sufficiently complete to provide key information for subsequent analyses.
• The participant or her legally authorized representative voluntarily signs written informed consent after being fully informed.

Exclusion Criteria:

• The participant has already received systemic anti-tumor treatment for the current ovarian/adnexal lesion under evaluation, such as chemotherapy, targeted therapy, immunotherapy, or radiotherapy, or has already undergone definitive tumor resection or comprehensive staging surgery, and is undergoing surgery only for residual or recurrent lesions.
• No pathologic diagnosis is ultimately obtained for the current ovarian/adnexal mass, or no analyzable pathologic conclusion can be established.
• Imaging findings at screening are highly typical of benign mature cystic teratoma.
• Ovarian cancer combined with another malignant tumor.
• There are obvious noncompliances during sample collection, transport, or processing, resulting in severe hemolysis, contamination, or seriously insufficient sample volume, such that the sample cannot meet quality control requirements for cfDNA methylation testing or subsequent analyses.
• Any other condition that, in the investigator's judgment, makes the participant unsuitable for enrollment.

Women with complex ovarian or adnexal masses, including suspected ovarian-origin pelvic masses, who are planned to undergo first-time surgery or biopsy/pathologic sampling related to the current lesion at participating centers and are expected to have a postoperative pathologic diagnosis available as the reference standard. The main analysis population consists of participants with pathologically confirmed early-stage invasive ovarian malignancies (FIGO 2014 stage IA-IIB) and participants with pathologically confirmed benign ovarian or adnexal diseases. Participants with borderline ovarian tumors, advanced-stage invasive malignancies, and, where available, high-risk or precursor lesions may also be enrolled as exploratory cohorts.

No individual participant data are planned to be shared at this time.