Ovarian cancer is a cancerous growth arising from the ovary. Symptoms are frequently very subtle early on and may include: bloating, pelvic pain, difficulty eating and frequent urination, and are easily confused with other illnesses.
Most (more than 90%) ovarian cancers are classified as "epithelial" and are believed to arise from the surface (epithelium) of the ovary. However, some evidence suggests that the fallopian tube could also be the source of some ovarian cancers.Since the ovaries and tubes are closely related to each other, it is thought that these fallopian cancer cells can mimic ovarian cancer. Other types may arise from the egg cells (germ cell tumor) or supporting cells. Ovarian cancers are included in the category gynecologic cancer.
 
Signs and symptoms
Most typical symptoms include: bloating, abdominal or pelvic pain, difficulty eating, and possibly urinary symptoms.
Other findings include an abdominal mass, back pain, constipation, tiredness and a range of other non-specific symptoms, as well as more specific symptoms such as abnormal vaginal bleeding or involuntary weight loss
Ovarian cancer is associated with age, family history of ovarian cancer (9.8-fold higher risk), anaemia (2.3-fold higher), abdominal pain (sevenfold higher), abdominal distension (23-fold higher), rectal bleeding (twofold higher), postmenopausal bleeding (6.6-fold higher), appetite loss (5.2-fold higher), and weight loss (twofold higher.
 
Cause

• Older women, and in those who have a first or second degree relative with the disease, have an increased risk.
• Hereditary forms of ovarian cancer can be caused by mutations in specific genes (most notably BRCA1 and BRCA2, but also in genes for hereditary nonpolyposis colorectal cancer).
• Infertile women and those with a condition called endometriosis.

Classification
 
A benign tumor of the ovary, discovered during a C-section; this is a 4 cm teratoma
Ovarian cancer is classified according to the histology of the tumor, obtained in a pathology report. Histology dictates many aspects of clinical treatment, management, and prognosis.

• Surface epithelial-stromal tumour, also known as ovarian epithelial carcinoma, is the most common type of ovarian cancer. It includes serous tumour, endometrioid tumor, and mucinous cystadenocarcinoma.
• Sex cord-stromal tumor, including estrogen-producing granulosa cell tumor and virilizing Sertoli-Leydig cell tumor or arrhenoblastoma, accounts for 8% of ovarian cancers.
• Germ cell tumor accounts for approximately 30% of ovarian tumors but only 5% of ovarian cancers, because most germ cell tumors are teratomas and most teratomas are benign. Germ cell tumors tend to occur in young women and girls. The prognosis depends on the specific histology of germ cell tumor, but overall is favorable.
• Mixed tumors, containing elements of more than one of the above classes of tumor histology.

 
Staging

• Stage I — limited to one or both ovaries
  • IA — involves one ovary; capsule intact; no tumor on ovarian surface; no malignant cells in ascites or peritoneal washings
  • IB — involves both ovaries; capsule intact; no tumor on ovarian surface; negative washings
  • IC — tumor limited to ovaries with any of the following: capsule ruptured, tumor on ovarian surface, positive washings
• Stage II — pelvic extension or implants
• IIA — extension or implants onto uterus or fallopian tube; negative washings
• IIB — extension or implants onto other pelvic structures; negative washings
• IIC — pelvic extension or implants with positive peritoneal washings

 
Ovarian adenocarcinoma deposit in the mesentry of the small bowel

• Stage III — peritoneal implants outside of the pelvis; or limited to the pelvis with extension to the small bowel or omentum
  • IIIA — microscopic peritoneal metastases beyond pelvis
  • IIIB — macroscopic peritoneal metastases beyond pelvis less than 2 cm in size
  • IIIC — peritoneal metastases beyond pelvis > 2 cm or lymph node metastases
• Stage IV — distant metastases to the liver or outside the peritoneal cavity