Why does cancer move?

“Metastasis” is a terrible word for cancer patients, and many patients hear it from their doctors, as if they were hit by a blow, and some even die.


The term “metastasis” refers to a malignant tumor (commonly known as “cancer”) that continues to grow outside the original site (the primary site). If it is transferred to the same organ, such as liver cancer metastasis to other liver, it is called “intrahepatic metastasis”; If not in the same organ, it is called “distant metastasis”. This trait, also known as diffusion, is one of the most important markers of benign and malignant tumors. Benign tumor generally will not be transferred, there are transferred, almost certainly is malignant, but means that has entered the late or malignant degree is higher, operation difficulty is bigger also, and even lost operation opportunity. Early malignancies are relatively less metastatic.

Why the shift? The current view is that cancer cells are more capable of growing than benign tumors, and even with poor growth conditions, several cancer cells can grow into a huge tumor. In addition, malignant tumor cells can secrete a lot of factors, namely small protein, stimulate blood-vessel growth around, give the nutrition, at the same time stimulate the environment tend to help tumor growth. So when the cancer cells along the blood vessels and lymphatic vessels in piping system drift to other organs in the body, such as, or fall off from the in situ tumor directly or after adhesion to a nearby organs, it is easy to grow in the viscera and form the metastatic lesions. There is also the suggestion that the genes of malignant tumor cells can change with environmental changes, and that new parts can better adapt to the surrounding environment. However, benign tumor growth is slow, the surrounding conditions are high, the gene is very stable, not easy to change, not easy to grow in other parts, it is not easy to transfer.

Many cancer will appear, such as the first incidence of lung cancer, metastatic rate is as high as 30% ~ 40%, and the transfer of the most common parts including the liver, brain, kidney, prostate, bones and lymph nodes, liver metastasis is most common among them, 33% ~ 40%. Women with the highest incidence of breast cancer, metastatic rate of about 10%, common sites including bone, lung, brain, liver and so on, the bone accounted for 47%~85%. The most common metastatic sites in colorectal cancer were the liver (33%), followed by lung (22%). Distant metastasis of prostate cancer is rare (3%), almost all in the bone. The incidence of gastric cancer is very high, and the metastasis rate is very high, over 50%, and the most common site is lymph nodes. The most common metastatic sites of liver cancer are lung (40%), lymph node (26%~37%), bone (28%) and adrenal gland (11%). These are common sites that focus on detecting cancer metastases.

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