This article will help you read and understand your ovarian cancer pathology report.
by Jason Wasserman MD PhD FRCPC, reviewed by our Patient Partners on August 3, 2020
Ovarian cancer is a disease that starts from cells normally found on the surface of the ovary, inside of the ovary, or in the fallopian tube. Unlike normal, healthy cells, cancer cells have the ability to grow and create new cancer cells very quickly. Cancer cells can also spread to other parts of the body such as the uterus, pelvis, abdomen, and lymph nodes.
The ovaries are part of the female reproductive tract. They are small, paired organs that are attached to the uterus by the fallopian tubes. The outer surface of the ovary and the inside of the fallopian tube are lined by specialized cells called epithelial cells that form a barrier called an epithelium.
Inside of the ovary are large, specialized cells called ova (a single ova is called an ovum). In adult women, these ova are released from the ovary during ovulation. The ova are also called germ cells because they have the potential to turn into any other type of cell in the body (the word germ comes from the Latin word for ‘seed’).
The ova are supported by granulosa and thecal cells that produce hormones such as progesterone and estrogen. The granulosa and thecal cells are surrounded by a type of tissue called stroma that is made up of long thin cells called fibroblasts.
There are many different types of ovarian cancer. Your ovarian cancer pathology report will say the type of ovarian cancer found in your ovary along with other important information that will help guide your care.
Tumours of the ovary are divided into three groups – carcinomas, germ cell tumours, and sex-cord stromal tumours – based on the type of cell that started the tumour.
The most common types of ovarian cancer start from the epithelial cells on the surface of the ovary or inside the fallopian tube. These cancers are called carcinomas. The type of carcinoma depends on how the tumour looks when examined under the microscope and the results of additional tests such as immunohistochemistry.
Types of carcinoma include:
Carcinomas are typically found in women over the age of 50 years and many have spread to other parts of the abdomen or pelvis by the time the diagnosis is made. Non-cancerous tumours that start from the epithelial cells are more common in women under the age of 50 years. Unlike the cancers listed above, the non-cancerous tumours do not have the word “carcinoma” or “malignant” in their name.
Tumours that start from the ovum are called germ cell tumours. When examined under the microscope, germ cell tumours can look like almost any type of tissue in the body including the tissues normally found in the placenta.
Types of germ cell cancers include:
The most common type of germ cell tumour is the non-cancerous mature teratoma (also called the mature cystic teratoma). Germ cell cancers are much less common.
Tumours that start from the steroid hormone producing cells inside the ovary are called sex-cord stromal tumours. Some of these tumours produce high levels of hormones such as estrogen, progesterone, and testosterone. These tumours are more likely to develop in women under 55- years of age.
Types of sex-cord stromal tumours include:
Ovarian cancer can only be diagnosed after a tissue sample has been examined under the microscope by a pathologist. This usually involves removing the entire tumour along with the ovary and fallopian tube. Your doctor may also recommend removing the uterus along with the ovary and fallopian tube on the opposite site of the body.
For some women, the diagnosis is made after a small sample of fluid is removed from the abdomen or pelvis in a procedure called a fine needle aspiration. The fluid and any cells in the fluid are placed on a slide and examined under a microscope. This type of procedure does not always allow your pathologist to determine the type of cancer. In this situation, the report may use the term “positive for malignancy” which means that a cancer was found in the fluid but that the type has not yet been determined.
After examining the tumour under the microscope, your pathologist will determine the type of ovarian cancer. This may involve doing additional tests such as immunohistochemistry. The type of ovarian cancer found is important because some types grow slowly and rarely spread to other parts of the body while other types grow quickly and commonly spread to other parts of the body. Knowing the cancer type will help your doctors predict the behavior of the disease and provide you with the best treatment options.
Some types of ovarian cancer are given a tumour grade. Grade is a word that pathologists use to describe how different the tumour cells look and behave compared to normal ovarian cells. The tumour grade is important because lower grade tumours tend to grow more slowly and are less likely to spread to other parts of the body while higher grade tumours grow more quickly and are more likely to spread early to other parts of the body.
Endometrioid and mucinous type carcinomas are given a grade between 1 and 3 based on the percentage of tumour cells that are growing as large groups of cells. Pathologists call this pattern solid growth. Another name for this system is the FIGO (Federation of Gynecology and Obstetrics) grading system.
Immature teratoma is given a grade of low or high based on the amount of immature or embryonal type tissue seen when the tumour is examined under the microscope.
Most ovarian cancer pathology reports will include the size of the tumour. However, the tumour size can only be determined if the tumour is received in one piece by the pathology laboratory. If the tumour is received in multiple pieces or if it was opened during the surgery, an approximate tumour size may be given in your report.
Most ovarian tumours start in the ovary. However, some tumours start in another location such as the fallopian tube, abdominal cavity, or appendix and spread to the ovary. For that reason, your pathologist will carefully examine the ovary and any other tissue received for any evidence that the tumour may have started somewhere other than the ovary.
Careful examination of the fallopian tube is important, especially if you were diagnosed with high grade serous carcinoma. The reason for this is because high grade serous carcinoma commonly starts in the fallopian tube and the tumour cells spread quickly to the surface of the ovary where tumour continues to grow. Patients with a family history of breast or ovarian cancer or a genetic change in the BRCA gene are at high risk for developing cancer in the fallopian tube.
A tumour that is seen on the outside of the ovary is more likely to have traveled there from another location such as the fallopian tube, appendix, abdominal cavity, or the ovary on the opposite side of the body. This is especially true if most of the tumour is seen on the outside of the ovary. Your doctor may suggest additional treatment if they suspect that the tumour started in another location and that some of the tumour may still be in your body.
At the time of surgery, your doctor will attempt to remove the entire tumour in one piece. This is done to prevent tumour cells from spilling out of the tumour and into the abdominal cavity or pelvis. Tumours that break (rupture) during surgery increase the risk that the cancer will re-grow or spread to other parts of the body.
Because the ovary is so close to other organs, it is not uncommon for tumour cells to spread directly from the ovary to organs such as the fallopian tube, uterus, colon, bladder, or omentum (the fatty tissue that surrounds the colon and small bowel). Tumour cells can also spread to the ovary or fallopian tube on the opposite side of the body.
In order to see if tumour cells have spread to any of these organs, your surgeon may remove small samples of tissue and send them to your pathologist to examine under the microscope. This examination is sometimes done while you are still in the operating room because the result can change the type of surgery performed. This is called a frozen section or intraoperative consultation.
The spread of tumour cells to other organs or tissues within the abdomen and pelvis is important because it is used to determine the pathologic tumour stage which is used to guide your treatment.
Tumour cells that have spread outside of the ovary to a lymph node or another part of the body are called a metastasis. Your surgeon may remove or take a small sample from lymph nodes from the abdomen or pelvis at the same time the tumour is removed to look for metastasis.
Your pathologist will carefully examine all lymph nodes to look for metastasis. The number of lymph nodes examined and the number with tumour cells will be described in your ovarian cancer pathology report. Your report will also include a measurement of the area with tumour cells in the lymph node.
This information is important because it is used to determine the pathologic stage.
The pathologic stage is a system used to describe the growth of the tumour and whether the tumour cells have spread to other parts of the body. The pathologic stage can only be determined after the entire tumour has been removed.
The pathologic stage is based on the TNM (Tumour, Nodes, Metastasis) system created by the American Joint Committee on Cancer. It is divided into three parts which describe the tumour (T), lymph nodes (N), and metastatic disease in other parts of the body (M). Most ovarian cancer pathology reports will only include information about the tumour and lymph nodes.
The pathologic stage is important because it is used to predict how the disease will progress over time (the prognosis). Your team of doctors will also use the pathologic stage to decide which treatment options are best for you.
Some patients inherit particular genes that put them at a much higher risk for developing ovarian cancer. These people are said to have a syndrome and the most common syndrome associated with ovarian cancer is called hereditary breast and ovarian cancer syndrome.
Patients with hereditary breast and ovarian cancer syndrome are at high risk for developing high grade serous carcinoma. Often the tumour starts in the fallopian tube but quickly spreads to the ovary. Hereditary breast and ovarian cancer syndrome is caused by a mutation in the BRCA1 or BRCA2 gene. The mutation causes the gene to produce a protein that is unable to function normally. This allows cells in the breast, fallopian tube, and ovary to grow and divide much faster than normal, healthy cells.
If you have been diagnosed with high grade serous carcinoma, your doctor may recommend genetic testing to look for BRCA1 or BRCA2 mutations.
Lymphovascular invasion – Tumour cells spread to lymph nodes or other parts of the body by entering blood vessels or another type of vessel called a lymphatic. Lymphovascular invasion means that your pathologist saw tumour cells inside either a blood vessel or a lymphatic vessel.