Ovarian Cancer: How Does Cancer Arise?

In order to understand what ovarian cancer is, let’s review some of the basics about how cancer develops in general. This is a condensed overview, and the references at the end are meant for those who want to go beyond this basic explanation of anatomy, reproductive physiology, genetics and the genesis of cancer.

Tissues, Organs & Building Blocks

Your body is made up of cells, the smallest building blocks that you can see under a microscope. Cells aggregate or come together in an orderly fashion and form various tissues, like skin, muscle, bone and your organs.

Just to get an idea of how many cells it takes to make tissues (both normal and abnormal), a one cubic inch area has approximately one billion cells connected together. Each cell is composed of a central nucleus surrounded by cytoplasm (fluid in the cell), all of which is contained within a cell membrane (outer thin covering).

The nucleus contains the genetic material contained in chromosomes, which harbor many different genes. Genes, in turn, are composed of deoxyribonucleic acid or DNA; the building blocks of life.

Whether tissues grow normally or develop into cancer depends upon how the genes interact with various environmental factors, like diet. In that sense all cancers, including ovarian, are genetic in nature. However, some occur spontaneously and are called "sporadic", whereas some can be passed on through generations and are called "familial". Discover the difference by exploring what genes have to do with it.

Your Ovaries

Ovaries are only found in women and are part of the reproductive system. There are two of them, located on either side of the uterus, deep in the pelvis. They vary in size depending upon age, usually measure about an inch or two during reproductive years and can shrink to the size of a peanut in post-menopausal years.

Ovaries exist to produce hormones (estrogen and progesterone mainly) and eggs for reproduction. The ovaries are made of different types of cells. The surface covering is made of epithelial cells.

The vast majority of ovarian cancers arise from the epithelial surface cells, but can also develop from internal cell types that make hormones and support and nurture the eggs in the ovary (germ cell and stromal). If the ovaries have to be removed during premenopausal years, it causes infertility, or inability to bear children from your own eggs.

Often, the uterus is removed as part of ovarian cancer surgery, in which case it is not possible to bear children even with donated eggs. In addition, removal of the ovaries during reproductive age will cause a sharp drop in estrogen levels and resulting symptoms of hot flashes and sweats.

Cancer Cell Types

Cancers can arise from many different cell types. In the ovary, more than 30 different cell types can become malignant. Those which develop from epithelial surfaces which line different organs are in a group called carcinoma. This is the most common group of cancers. If the lining is glandular, then the name is extended to adeno-carcinoma. For example, the cells which line the colon, internal cervix and uterus, breast tissue, prostate or ovary are in this grouping. Functional cells which support ovarian eggs can also become malignant and are called germ cell or stromal cancers. Cancers can also arise from various cells and structures such as bone, muscle, and fat and are referred to as sarcomas. These are rare, but can also occur within some gynecologic organs like the uterus and ovaries. Beyond these general categories there is a large list of uncategorized, unusual or rare cancers.

Benign and Malignant or Cancerous Ovarian Tumors

Although the word “tumor” is often used interchangeably with the word “cancer,” in fact tumors can be either benign or malignant. Fortunately, most tumors of the ovary are benign or non-cancerous. However, benign tumors can cause problems in the pelvis by growing large enough to cause pain or pressure symptoms. Unlike ovarian cancer, they do not spread and are not life threatening. Treatment of benign tumors is usually surgical, by removing all or part of the ovary with a growth or tumor on it.

The ovaries can also start growing cancerous or malignant tumors. Ovarian cancer is much more serious since it can spread and, if not treated aggressively, can lead to death. Treatment usually starts with surgery, which is why it is important to know your anatomy in order to understand how this treatment will affect you.

Early Ovarian Cancer

When ovarian cancer first starts growing in the ovary and spreading locally in the pelvis it may not be detectable. That pea-sized mass referred to earlier can be undetectable by pelvic examination or scans. When it starts to grow locally by enlarging the ovary or spreading onto other pelvic structures, a pelvic examination or scan may detect masses or nodules that may still be confined to the pelvis. However, the exact point at which cancer cells can microscopically break off and spread or metastasize is unpredictable.

Ovarian Cancer Spread or Metastases

Once ovarian cancer spreads beyond the ovary to lymph nodes or other parts of the abdomen it is no longer “early." How far the cancer has spread is categorized by "stage" and how it looks under a microscope is called a "grade." Stage and grade are the most important factors which predict the chances of cure. Treatment for ovarian cancer is often based on the fact that in the majority of cases, it remains confined to the abdomen and does not spread to the lung, brain or bones until very late in its development.

_Source:

National Cancer Institute PDQ Database.