In layman’s terms, tumors, or cancer, are actually a group of diseases. Why do you say so? It is a disease caused by abnormalities in the morphology, structure and function of normal cells. There are three characteristics: tumor cells have strange morphology. Normal cells have their own inherent morphology after it develops and matures, and so do the cells. People differentiate from an embryonic cell, slowly more and more, some become nerve cells, some become organs, skin and so on and they are stereotyped. For example, liver cells are the appearance of liver cells, skin cells are the appearance of skin cells. Like human beings, although there are Zhang San and Li Si, fat and thin, tall and short, all are human-like, all have eyes, nose and mouth, the basic characteristics are the same. However, tumor cells are different, they are in a low differentiation or undifferentiated state. Some characteristics of normal cells are gone, and they become deformed like human beings, and become a freak. It is the anarchic growth of tumor cells. The normal cell growth is very strictly controlled by the organism, if the organism needs you to grow, you will grow, if not, you cannot grow. For example: human skin cells, the third layer of cells can divide and produce normal cells, while the epidermal cells, there is no regeneration ability. We take a bath and rub down a layer of mud. What is this stuff? This is essentially a kind of epidermal cells, the second or third layer of cells continue to grow. Otherwise, infinite growth, then the skin will be the same as the elephant. These growths are controlled by the organism. But when you are injured and pull a gash, the cells on both sides of the incision multiply and slowly heal the wound. These two sides of the cells touch one another and immediately stop growing. If they don’t stop, this scar will get bigger and bigger. The human body has such a very strict control system. I am using skin cells as an example. Cancer cells are not under the control of the central government, they grow as much as they like and multiply in a completely anarchic way. The more they multiply, the more lumps are formed. This lump is not needed by the body, it can absorb your nutrition and produce some harmful substances to the body. Cancer cells have the ability to invade and metastasize. We know that where normal cells should be, it is there. For example, skin cells are on the skin, muscle cells are on the muscle, bone cells are on the bone, liver cells are on the liver, they cannot run away. Cancer cells are different, they can run around and invade other places. It keeps multiplying and infiltrating into other tissues, and it can also run to far away. Therefore, those with the above three characteristics are cancer cells. When countless cancer cells gather together, they form tumors. Just because cancer cells have those three characteristics, we can imagine the harm it does to human body. The difference between tumor cell division and normal cell division So, unlike normal cells, do cancer cells grow faster? Do normal cells grow slower? I can tell you that many people thought so at first, but later through experiments, they found that it is not so. The process of cancer cell division is exactly the same as that of normal cells. The process of a cancer cell dividing takes about 50-60 minutes, like an hour! This is also true for normal cells. Also we know that between two cells dividing, it has an interval. Some of them are longer, some are shorter. When it gets to the division phase, it starts dividing. So there’s a second thought. Is there a difference between these two cell divisions? Is it that the cancer cells are shorter and the normal cells are longer? Is it possible that the cancer cells are growing faster and faster? After further experiments, it was found that the pre-cell division period is very important. Because during this period, a large amount of, how to say it, called chemosynthesis! The contents of a cell before division is equal to two cells, after division, a cell divides into two smaller ones, and the smaller ones divide into smaller ones again, and finally they are gone. This stage is very important. After research again: normal cells and tumor cells divide in about the same interval. So, here’s the problem. Why do tumor cells divide so quickly and slowly form tumors when the division interval is the same and the pre-division interval is also similar? What is the reasoning? As I said earlier, most of the normal cells do not divide under normal conditions. Like the skin mentioned earlier, it can divide normally and has the ability to reproduce is the latter two layers, but the rest cannot divide and reproduce. Some cells in the human body, such as nerve cells, stop reproducing after birth, do not divide and mature. Other cells also divide and reproduce again as needed. This is not the case with tumor cells, the vast majority of which are dividing and multiplying to varying degrees. This poses a problem, getting larger and larger, dividing and growing into the territory of their neighbors. The different growth characteristics of benign tumors and malignant tumors Benign tumors, they do not metastasize. It has an outer layer of envelope, like a city population, which is strictly controlled and cannot run outside and wrap up. Its cell differentiation, also similar to normal cells, does not have the ability to infiltrate and will not break through the envelope to grow outside. This is not the case with malignant tumors. It can secrete some things that normal cells do not have. For example, it can secrete enzymes that dissolve the surrounding tissues, produce a factor that induces the surrounding tissues to produce new capillaries, and so on. As the cancer cells multiply anarchistically and grow to a certain extent, they invade into small blood vessels through the walls of blood vessels and run into the lymphatic vessels through the walls of lymphatic vessels. In this way, the tumor cells run away and travel away, traveling along the blood vessels and lymphatic vessels. Ways and modes of tumor metastasis There are three ways of tumor cell metastasis: naval, land and air. 1.Naval way So, does the cancer cells going out mean metastasis? Not necessarily. In our human body, there is still a very strong immune ability or resistance ability. There are a lot of immune lymphocytes in the blood vessels and lymphatic vessels, and most of the tumor cells that enter the “waterway” will be destroyed by the human body eventually. Then when does metastasis occur? When a cancer cell goes out, it stays in a place and takes root, just like a mobile account settling in a foreign country, it can take root, then it may multiply and metastasize. So, what can we imagine? In terms of vascular shape, it can stay down where it must be very rich in blood vessels, and the vascular network is particularly large. It can’t stay in the large vessels. Has anyone heard of a metastasis in this patient’s aorta? No. It’s like a tunnel. Like tunnels, the sludge in the large vessels is not easily survived. When you go to the smallest vessel, the flow rate slows down and the cells can’t stay down. Then what is the place where there are many small blood vessels and there are many capillary sinuses, very small and tiny. The tumor cells come here and stay, or the place is slightly damaged, the wall is not smooth, it will stay. If they stay and take root, it’s bad and they have to multiply. Because it has these characteristics, it will not produce metastasis when it flows. The liver is a place, the lungs are a place, and the bones. There are places in the bones where cartilage meets, or in the bone marrow cavity, where there are more capillaries. Or sometimes it goes to the brain. Muscle is less easy to get to because muscle is not a vascular tissue, and muscle moves and contracts a lot. Fatty tissue is also not easy to go. Whatever goes from the blood vessels is most likely to move to the liver, lungs, brain, and bone. Going from the waterways, there is another route – the lymphatic vessels. There are lymphatic tissues in human body, which are very much like railroad network, lymphatic vessels are like railroad and lymph nodes are like stations. Generally speaking, from a tumor point of view, lymph nodes are divided into about four stations. Take the colon for example, the lymph node next to the intestine is the first station, we call it paracolonic lymph node. The lymph nodes next to the intestine are the first station, which are called paracolonic lymph nodes. Then, the lymph nodes in the mesenteric vessels of the colon are the second station. Then, it goes to the root of the mesentery. Because the course of the lymphatic vessels is generally the same as that of the blood vessels, the third lymph node, which is also near the root of the blood vessels. It can go further, let’s say to the side of the abdominal aorta, and that’s the fourth station. Of course, it can go further, and we call it distant metastasis in a general way. For example, in digestive tract cancer, the most common metastasis is to the left supraclavicular lymph node. Why? Because all the lymphatic fluid in the digestive tract, including the lymphatic fluid absorbed from the small colon, finally comes to the abdominal aorta and goes up to a place called the celiac pond, and finally goes to the subclavian vein. The lymphatic vessels that eventually converge into this vein are called thoracic ducts, and there are lymph nodes at the entrance of this place. The enlarged lymph nodes in this area mean that the cancer cells coming through the lymphatic duct have passed the first line of defense, the second line of defense, the third line of defense, the fourth line of defense, and finally the runway to the blood. So the lymph nodes in each place are actually one stop of defense. The tumor cells come off from the tumor and enter the nearby lymphatic vessels. It’s like fighting a war, the enemy is coming from the first trench, but they haven’t breached my bunker yet! I am still holding here! The lymph nodes have an input lymphatic vessel and an output lymphatic vessel, and the lymph in this area is very thin. This leaves two possibilities. One is that it is possible to destroy the lymph node because of the large concentration of service-free lymphocytes in it. Another possibility is that it wipes out our defense forces, and it takes over the bunker and just keeps multiplying and growing. For example: a patient suffering from breast cancer should check whether the axillary lymph is big or not, if this lymph node is big, it is likely to have been occupied by it. For example, if stomach and liver are adjacent to each other, when stomach cancer infiltrates outward, it can pass through the stomach wall and invade the liver, causing liver metastasis. Generally speaking, direct invasive metastasis has better treatment effect than the kind of metastasis I just mentioned. Because we can do surgery to remove gastric cancer together with the infiltrated lesions to the liver, the effect is the same. If the metastasis is from the blood vessel to the liver, the effect is different, and this surgery cannot be done. This surgery cannot be done because the larger one is removed, but the smaller one is still growing. This is of little practical importance. But direct infiltration is a different story. This is the “land army” transfer, direct infiltration. 3.Airborne way How to talk about airborne? Let’s take gastric cancer as an example. Gastric cancer develops gradually, from gastric mucosa to submucosa, then to muscle layer, then to plasma membrane, to plasma membrane, and the tumor grows out. The tumor cells on the surface of the plasma membrane then fall down and fall into the abdominal cavity. Like a seed, it is planted there, and it metastasizes there, and we call it an implantation site. That’s why doctors have to check the anus when examining patients with stomach or intestinal cancer. If it falls down, it will be airborne at the bottom of the abdominal cavity, that is, the pelvic floor. We call it the cysto-rectal fossa, which is the lowest place in the human abdominal cavity. If a lump is felt on finger examination, it means that it has metastasized here. But even if it falls airborne in the abdominal cavity, it doesn’t always metastasize, most of it is also eliminated, and the ones that do metastasize, are still a minority. This is the question that people ask about why it can metastasize.