How long does ovarian cancer take to develop into stage 3/4?

This hard question: Ovarian cancer, as well as any other type of cancer, is also graded, apart from staged. The histologic grade of a tumor measures how abnormal or malignant its cells look under the microscope.[42] there are four grades indicating the likelihood of the cancer to spread and the higher the grade, the more likely for this to occur. Grade 0 is used to describe non-invasive tumors. Read below?

Hard to know: Most ovarian cancers are already stage 3 or 4 when they are diagnosed so we really don't know how long it took them to get there. In retrospect, many women have had symptoms for many months before their diagnosis. There may also be an asymptomatic stage that could last for months or even years before the symptoms begin.