What is the cause of metastatic liver cancer? Introduction to 4 causes of metastatic liver cancer

Malignant tumors can directly infiltrate surrounding tissues, or invade lymphatic vessels, blood vessels and body cavities, and then cancer cells are transferred to distant places with lymph, blood and various cavities. The infiltration and metastasis of cancer cells mainly depend on their own malignant biological characteristics and the body's immune status. Cancer cells have amoeba-like activity and can autonomously infiltrate and move to surrounding tissues; adhesion between cancer cells is the mutual attraction between the contact parts of two different substances.

Decreased expression of certain integrins in cancer cells may give cancer cells the power to migrate, making it easier for them to penetrate the basement membrane; certain adhesion molecules in the body help cancer cells to stay in metastatic organs; increased activity of proteolytic enzymes on the surface of cancer cells is also conducive to their infiltration and metastasis. Since most tumor-bearing hosts have low immune function and cannot effectively identify and kill metastatic cancer cells, once cancer cells stay in distant organs, they can release a variety of growth factors and their receptors, such as vascular endothelial growth factor (VEGF), allowing cancer cells to grow autonomously and without restrictions. This malignant biological characteristic of cancer cells is related to the genetic information they carry, such as DNA ploidy or stem cell level. Aneuploid cancer cells are more likely to metastasize than diploid cancer cells. Due to its own anatomical and blood supply characteristics, the liver may be more likely to provide a variety of cancer cells with growth space and nutrient sources for retention. There are four ways for cancers in various parts of the human body to metastasize to the liver: portal vein, hepatic artery, lymphatic pathway, and direct infiltration.

1. Portal vein metastasis: Any malignant tumors in organs whose blood flows into the portal vein system, such as the lower end of the esophagus, stomach, small intestine, colorectum, pancreas, gallbladder and spleen, can metastasize to the liver through the portal vein. This is an important way for primary cancer to spread to the liver. It has been reported that there is a shunt phenomenon in the portal vein blood flow, that is, the blood flow of the splenic vein and the inferior mesenteric vein mainly enters the left liver, while the blood flow of the superior mesenteric vein mainly flows into the right liver. Tumors in organs belonging to these portal veins will metastasize to the corresponding parts of the liver due to different blood flow directions. However, clinically, the shunt of this tumor metastasis is not obvious, and scattered metastasis of the whole liver is more common. Other cancers such as uterus, ovary, prostate, bladder and retroperitoneal tissue can also metastasize to the liver through the anastomotic branches of the systemic vein or portal vein; they can also metastasize to the liver because the tumor growth in these parts invades the organs of the portal vein system; or they can first spread from the systemic vein to the lungs, and then from the lungs to the whole body circulation to the liver.

2. Hepatic artery metastasis Any cancer that spreads through the blood can metastasize to the liver through the hepatic artery. For example, malignant tumors in the lungs, kidneys, breasts, adrenal glands, thyroid glands, testicles, ovaries, nasopharyngeal can spread to the liver through the hepatic artery. Metastasis to the liver is also common.

3. Lymphatic metastasis Pelvic or retroperitoneal cancer can metastasize to the para-aortic and retroperitoneal lymph nodes via lymphatic vessels, and then flow back to the liver. Gastrointestinal cancer can also metastasize to the liver via the portal lymph nodes along the lymphatic vessels. Breast cancer or lung cancer can also metastasize to the liver via the mediastinal lymph nodes, but this metastasis is less common. Clinically, gallbladder cancer is more common in metastases to the liver along the lymphatic vessels of the gallbladder fossa.

4. Cancers that directly infiltrate organs adjacent to the liver, such as gastric cancer, transverse colon cancer, gallbladder cancer, and pancreatic cancer, can spread to the liver due to direct infiltration of cancer cells due to adhesion between the cancer and the liver. Cancer of the right kidney and adrenal gland can also directly invade the liver.