Epithelial ovarian cancer (OC), including fallopian tube and primary peritoneal cancer, is the deadliest gynecologic malignant neoplasm with a 5-year relative survival of approximately 50%. This study will evaluate the concordance in folate receptor alpha (FRa) immunohistochemistry (IHC) in adult female participants with ovarian cancer.

Archived tissue biopsies will be tested for FRa and data from approximately 1,000 participants will be collected. This is a retrospective study and testing will be performed prospectively on archived samples.

Participants' charts will be reviewed. No drug will be administered as a part of this study. The duration of the study will be approximately 1 Year.

There is no additional burden for participants in this trial.

Inclusion Criteria:

• Surgical or biopsy samples (Formalin Fixed Paraffin Embedded [FFPE]) with tumoral High Grade Serous Ovarian Cancer (HGSOC) material allowing the sectioning of serial slides for all the analyses.
• Archival specimens should not be older than 5 years in order to control quality of the samples.
• Specimens containing a minimum of 100 viable tumor cells.

Exclusion Criteria:

• Surgical or biopsy samples (FFPE) with insufficient quantity or quality (sampled more than 5 years ago and/or with less 100 viable tumor cells per section).
• Tissue obtained following treatment with Mirvetuximab soravtansine or any other FRa targeted therapy.
• Tissue obtained through fine needle aspirations or liquid specimens, or ascites

The study population is surgical or biopsy sample from an adult female with tumoral High Grade Serous Ovarian Cancer.