How is ovarian cancer diagnosed?

Biopsy: (see similar question/answer). Most (all?) cancers need a biopsy to be definitively diagnosed. Tests such as imaging (eg, pelvic ultrasound) or laboratory tests (eg, ca-125) may be suspicious for ovarian cancer, but a biopsy and pathology study needs to be done.

Tissue examination: Symptoms of ovarian cancer are vague and physical examination may reveal a mass. There are many causes of a mass in the ovary and once a diagnosis is suspected, it requires removal of tissue and examination by a pathologist for definitive diagnosis. See this site for more info http://www.Cancer.Org/cancer/ovariancancer/detailedguide/ovarian-cancer-diagnosis.