Ovarian cancer originates from abnormal cell growth in the ovaries or fallopian tubes. It often presents with subtle, vague symptoms, making early detection challenging. Understanding its progression is important for determining treatment and outcomes.
Primary Pathway of Spread
Ovarian cancer most commonly spreads within the peritoneal cavity, the space containing abdominal organs. This occurs through direct shedding, where cancer cells detach from the primary tumor on the ovary or fallopian tube. These cells then float freely in the peritoneal fluid, which circulates throughout the abdomen. Fluid dynamics, influenced by gravity and respiratory movements, can carry these cells to various surfaces within the cavity.
The cells can then implant and grow on other abdominal organs. Common initial sites of spread within the peritoneal cavity include the omentum, a fatty tissue covering the intestines, and the surface of the diaphragm. The bowel surface and the liver capsule, the outer layer of the liver, are also frequent sites for these implants. This transcoelomic spread is the predominant initial pathway due to the ovaries’ anatomical proximity to the peritoneal lining and the movement of peritoneal fluid.
Other Routes and Distant Sites
Beyond the peritoneal cavity, ovarian cancer can spread through other pathways, indicating more advanced disease. One route is through the lymphatic system, where cancer cells travel via lymphatic fluid to nearby lymph nodes. These include the pelvic lymph nodes and the para-aortic lymph nodes, located along the aorta in the abdominal area. Lymph node involvement is common in advanced ovarian cancer cases.
Another pathway is hematogenous, or bloodstream, spread, though this is less common initially than peritoneal dissemination. Cancer cells can enter the bloodstream and travel to distant organs throughout the body. Common distant sites affected by blood-borne spread include the lungs, the liver parenchyma (the main tissue of the liver, as distinct from its capsule), and, less frequently, the brain or bones. The presence of cancer in these distant locations signifies a later, more advanced stage of the disease.
Understanding Staging and Spread
Medical professionals use cancer staging systems, such as the FIGO (International Federation of Gynecology and Obstetrics) system, to classify the extent of ovarian cancer spread. This system helps determine the disease’s progression and guides treatment decisions.
Stage I indicates that the cancer is confined to one or both ovaries or fallopian tubes. In Stage II, the cancer has spread beyond the ovaries but remains within the pelvis, affecting organs like the uterus or bladder. Stage III signifies cancer spread outside the pelvis to the peritoneal lining of the abdomen and/or to regional lymph nodes, including pelvic and para-aortic nodes. This stage directly relates to the initial peritoneal spread. Stage IV is the most advanced stage, where the cancer has spread to distant sites, such as the liver parenchyma, lungs, or other organs outside the abdominal cavity.