Overview

Ovarian cancer is a growth of abnormal malignant cells that begins in the ovaries (women’s reproductive glands that produce ova). Cancer that spreads to the ovaries but originates at another site is not considered ovarian cancer. 

Ovarian tumors can be benign (noncancerous) or malignant (cancerous). Although abnormal, cells of benign tumors do not metastasize (spread to other parts of the body).  Malignant cancer cells in the ovaries can metastasize in two ways:  directly to other organs in the pelvis and abdomen (the more common way), through the bloodstream or lymph nodes to other parts of the body.

While the causes of ovarian cancer are unknown, some theories exist: Genetic errors may occur because of damage from the normal monthly release of an egg. Increased hormone levels before and during ovulation may stimulate the growth of abnormal cells.

Types of Ovarian Cancer

Different types of ovarian cancer are classified according to the type of cell from which they start.

Epithelial tumors – About 90 percent of ovarian cancers develop in the epithelium, the thin layer of tissue that covers the ovaries. This form of ovarian cancer generally occurs in postmenopausal women.

Germ cell carcinoma tumors – Making up about five percent of ovarian cancer cases, this type begins in the cells that form eggs. While germ cell carcinoma can occur in women of any age, it tends to be found most often in women in their early 20s. Six main kinds of germ cell carcinoma exist, but the three most common types are: teratomas, dysgerminomas, and endodermal sinus tumors. Many tumors that arise in the germ cells are benign.

Stromal carcinoma tumors – Ovarian stromal carcinoma accounts for about five percent of ovarian cancer cases. It develops in the connective tissue cells that hold the ovary together and those that produce the female hormones estrogen and progesterone. The two most common types are granulosa cell tumors and sertoli-leydig cell tumors. Unlike with epithelial ovarian carcinoma, 70 percent of stromal carcinoma cases are diagnosed in Stage I.

Small cell carcinoma of the ovary – Small Cell Carcinoma of the Ovary (SCCO) is a rare, highly malignant tumor that affects mainly young women, with a median age at diagnosis of 24 years old.  The subtypes of SCCO include pulmonary, neuro-endocrine and hypercalcemic.  SCCO accounts for 0.1% of ovarian cancer cases. Approximately two-thirds of patients with SCCO have hypercalcemia. The symptoms are the same as other types of ovarian cancer.

Stages of Ovarian Cancer

The stages of ovarian cancer are determined by how far the cancer has spread. The stage of ovarian cancer at diagnosis is the most important indicator of prognosis.

Stage I – Cancer is limited to one or both ovaries.

IA – Cancer is limited to one ovary and the tumor is confined to the inside of the ovary. No ascites containing malignant cells is present, and the surface of the tumor has not ruptured.

IB – Cancer is limited to both ovaries without any tumors on the ovaries’ outer surfaces. No ascites containing malignant cells is present, and the surface of the tumor has not ruptured.

IC – The tumor is classified as either Stage IA or IB and one or more of the following conditions exist:

  • a tumor on the outer surface of one or both ovaries;
  • at least one ruptured tumor;
  • ascites or abdominal (peritoneal) washings containing malignant cells.

Stage II – The tumor involves one or both ovaries and extends to other pelvic structures.

IIA – The cancer has extended to and/or involves the uterus and/or the fallopian tubes.

IIB – The cancer has extended to the bladder or rectum.

IIC – The tumor is classified as either Stage IIA or IIB and one or more of the following conditions exist:

  • a tumor on the outer surface of one or both ovaries;
  • at least one ruptured tumor;
  • ascites containing malignant cells or abdominal (peritoneal) washings containing malignant cells.

Stage III – The tumor involves one or both ovaries, and one or both of the following exist:

  • The cancer has spread beyond the pelvis to the lining of the abdomen;
  • The cancer has spread to the lymph nodes. The tumor is limited to the true pelvis but with histologically-proven malignant extension to the small bowel or omentum (peritoneum fold).

IIIA – The tumor is in one or both of the ovaries. While surgeons cannot see cancer in the abdomen, and the cancer has not spread to the lymph nodes, biopsies checked under a microscope reveal tiny deposits of cancer in the abdominal (peritoneal) surfaces.

IIIB – The tumor is in one or both ovaries, and deposits of cancer are present in the abdomen that are large enough for the surgeon to see but do not exceed two cm in diameter. The cancer has not spread to the lymph nodes.

IIIC – The tumor is visible in one or both ovaries, and one or both of the following conditions exists:

  • the cancer has spread to lymph nodes;
  • the deposits of cancer exceed two cm in diameter and are found in the abdomen.

Stage IV- Growth of the cancer involves one or both ovaries and distant metastases to the liver or lungs have occurred. Finding ovarian cancer cells in the excess fluid accumulated around the lungs (pleural fluid) also shows evidence of stage IV.

For more specific information about ovarian cancer, see the American Cancer Society’s Detailed Guide.