Ovarian cancer accounts for less than 1.3% of all cancer cases, but 2.3% of all cancer deaths. With an estimated 22,440 new cases of ovarian cancer diagnosed each year, a woman has a 1 in 79 chance of developing invasive ovarian cancer in her lifetime.
Types of Ovarian Cancer
Ovarian cancer is classified based on the cells in which the cancer starts. Most cases are divided into three distinct types:
- Surface Epithelial Tumors begin in the cells covering the outer layer of the ovaries.
- Germ Cell Tumors begin in cells that develop into ova or eggs.
- Stromal Cell Tumors originate in cells that release hormones and connect the different structures within the ovaries
Surface Epithelial Tumors
Epithelial tumors account for 85 to 90% of ovarian cancer cases. These are among the most dangerous due to the fact that 70% of these cases will not be diagnosed until the cancer enters its later stages.
Five-year survival rates for Stage I epithelial tumors are as high as 90%. By the time the cancer has progressed to stage IV, survival rates drop to 17%.
Germ Cell Tumors
Germ cell tumors develop from the cells that produce eggs and account for 5% of all ovarian cancer cases. Most germ cell tumors are benign, meaning not harmful, but some, are malignant, meaning cancerous.
Germ cell tumors are most common in teens and women in their early twenties and 90% of these tumors are curable without affecting future fertility.
Stromal tumors develop from cells in the ovaries’ connective tissue and those which produce the female hormones estrogen and progesterone. They are considered low-grade cancers, meaning the cells are slow-growing and look almost normal under a microscope. When diagnosed at stage I, such cancers have a 95% survival rate.
Ovarian Cancer Stages
In addition to identifying the type of cancer, gynecologic oncologists must also determine the stage of a cancer’s development. Ovarian cancer stages are determined during exploratory surgery to assess the size of the tumor and whether cancerous cells have spread (metastasized) to other organs.
Ovarian cancer is assigned four stages, represented by the Roman numerals I, II, III, and IV. Each stage is divided into subcategories that influence treatment options. Generally, catching ovarian cancer in the earlier stages offers a better prognosis.
Ovarian Cancer Stages: Stage I
Stage I ovarian cancer indicates cancerous cells are confined to the ovaries. Stage I is divided into three subcategories:
- IA: the cancer is confined to a single ovary
- IB: the cancer is present in both ovaries
- IC: the tissue or capsule enclosing the tumorous cells has ruptured in one or both ovaries
Stage IC is further divided into three possible subcategories:
- IC1: the capsule enclosing the tumor ruptured during surgery
- IC2: the capsule ruptured prior to surgery
- IC3: the pelvic or abdominal fluid contains cancerous cells
Ovarian Cancer Stages: Stage II
Stage II ovarian cancer indicates the cancer has extended into the pelvis in addition to one or both ovaries. Stage II is broken down into two subcategories:
- IIA: the cancer extends into the fallopian tubes or uterus
- IIB: the cancer extends into the uterus, bladder, sigmoid colon, rectum, and/or other pelvic organs
Ovarian Cancer Stages: Stage III
By stage III, ovarian cancer has spread from one or both ovaries to beyond the pelvis and is divided into three subcategories:
- IIIA: evidence of cancerous cells is found in the lymph nodes or upper abdomen
- IIIB: a visible tumor of less than 2cm in size is located in the upper abdomen
- IIIC: a visible tumor exceeding 2cm in size exists in the upper abdomen, and presents evidence that the cancer has extended to the spleen or liver
Ovarian Cancer Stages: Stage IV
Stage IV is the most advanced of the ovarian cancer stages and presents evidence of metastasis throughout the body. Stage IV is split into two subcategories:
- IVA: cancerous cells are present in fluid surrounding the lungs
- IVB: cancerous cells have spread to the lung, liver, and/or spleen
Ovarian Cancer Grades
In addition to determining ovarian cancer stages, gynecologic oncologists and pathologists assign a tumor grade to cancerous cells. A tumor grade describes how healthy tumor cells look under a microscope. Cancer cells resembling normal cells usually indicate a slower spreading cancer. Six possible ovarian cancer grades exist:
- GX: the tumor cells cannot be evaluated
- GB: cells are considered borderline cancerous or of low malignant potential
- G1: the tissue sample contains many healthy-looking (well-differentiated) cells
- G2: the tissue sample has more abnormal (poorly differentiated) cells than healthy-looking cells
- G3 / G4: the sample contains increasing amounts of abnormal cells and tissue structures
Understanding ovarian cancer stages and grades helps women take an active role in their own treatment as they work with their oncologists to design the most effective treatment plan for themselves.