Origin, epidemiology, and histological classification
Approximately 90% of malignant cancers of the ovary are epithelial tumours; the remainder are stromal or germ cell tumours. Epithelial ovarian cancer is the commonest cause of death from gynaecological cancer in the developed world.
There are approximately 240,000 new cases each year. The approximate lifetime risk of developing the disease is 1.7%, but higher risks are seen in some regions, and in particular in women with a BRCA gene mutation who have about a 60% chance of developing ovarian cancer. The median age of onset is 60 years, but it is earlier in women with an inherited predisposition to the disease. The 5-year survival in many countries has improved over the last 30 years, probably due to a combination of better surgery and more effective systemic treatments. Nevertheless, the maj ority of women present with advanced disease and ultimately die of disease due to the development of resistance to systemic therapies.The majority of malignant tumours arising from the ovary, fallopian tube, or peritoneum are high-grade serous-type; other histotypes (endometrioid, clear cell, and mucinous) are rarer and have a different biological behaviour. A unifying hypothesis has been proposed in which high-grade tumours (type II) originate from the fimbrial end of the fallopian tube, and may present commonly as ovarian cancer, and less commonly as primary fallopian tube or peritoneal cancers (1). Low-grade epithelial (type I) tumours develop from the ovarian surface and have a distinct molecular profile and different biological behaviour. Stromal tumours are rare and are often localized to the ovary at presentation. Germ cell tumours are a rare subgroup of tumours that present in a younger age group.