Ovarian cancer is a common malignancy of the female reproductive system. In Western society it is less common than endometrial cancer but more common than cervical cancer. There are numerous groupings of ovarian cancers:
- Surface epithelial-stromal tumours, which are thought to arise from the mesenchymal tissue that overlies the ovary. This is by far the largest group.
- Sex-cord stromal tumours, which arise from the ovarian tissue itself
- Tumours of the rete ovarii
- Miscellaneous tumours
- Tumour-like conditions
- Lymphoid and haematopoetic tumours
Each of these groups has distinctive aetiology, pathogenesis and histological features and are considered separately.
The surface epithelial-stromal tumours are the largest group of ovarian neoplasms. They are either malignant (e.g. serous adenocarcinoma), borderline (borderline serous tumour) or benign (serous cystadenoma). They are less common in women who use the contraceptive pill or who have high parity, possibly due to suppression of follicle ruptures and reduced scarring of the surface of the ovary. There is evidence that diet may have a role to play given the higher incidence in Western countries. They are classified by the dominant cell type or architecture - serous (papillary structures, psammoma bodies), mucinous (contains mucin), endometrioid (endometrioid pattern), clear cell or transitional cell (often called Brenner tumours).
Germ cell tumours make up 30% of ovarian neoplasms. The majority are benign mature teratomas, of which the most common form is the dermoid cyst (large cyst filled with hair and sebaceous fluid). Immature teratoma (1% of neoplasms) and other primitive germ cell tumours (most common dysgerminoma or mixed germ cell tumour) make up about 2% of all ovarian tumours. The primitive germ cell tumours are the most common malignant tumours of childhood and young adulthood.
The sex cord-stromal tumours form the smallest of the main categories, accounting for about 8% of primary ovarian malignancy. They are divided into four groups: the granulosa-stromal tumours, the most common group; Sertoli-stromal tumours, which form tubules and may produce androgens; and two smaller groups (mixed and steroid) which are even rarer. The most common during childhood and young adulthood are the Sertoli-stromal tumours and mixed tumours, whereas the granulosa-stromal and steroid tumours usually occur in post-menopausal women.
Ovarian tumours are all staged by FIGO/TNM which has a matching system.
IA - Confined to one ovary, no surface involvement
IB - Confined to one ovary, surface involvement
IC - Bilateral ovarian involvement
II - Involvement of adjacent pelvic structures
III - Involvement of abdominal structures except liver
IV - Distant metastases