In layman’s terms, tumors, or cancer, are actually a group of diseases. Why do you say so? It is a disease caused by the abnormal function of normal cells in form and structure. What are its characteristics? The first feature is that tumor cells have strange morphology. Normal cells have their own inherent morphology after they mature, and so do cells. People differentiate from an embryonic cell, slowly more and more, some become nerve cells, some become organs, skin and so on and then 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. The second characteristic 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 an epidermal cell, 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 mass is not needed by the organism, it can absorb your nutrition and produce some harmful substances to the organism. The third characteristic is that cancer cells have the ability to invade and metastasize. We know that where normal cells should be, it is where it is. 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, it was found that this is not the case. The process of cancer cell division is exactly the same as that of normal cells. A cancer cell takes about 50-60 minutes to divide, like an hour! Normal cells do the same thing. 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 cancer cells are short and normal cells are long? What about the fact 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, call it chemosynthesis! The content of a cell before division is equal to two cells, after division, a cell divides into two smaller ones, the smaller ones divide into smaller ones again, and finally it is 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. Since the division interval is the same and the pre-division interval is also similar, why do tumor cells divide so fast and slowly form tumors? What is the reasoning? Later, I realized that, as I said earlier, most of the normal cells are actually not dividing under normal circumstances. 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, which 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. The cell differentiation of the tumor is similar to that of normal cells, which do 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. The ways and modes of tumor metastasis: There are three ways of tumor cell metastasis: naval, land and air. Firstly, the naval way is the “water way”, which goes out along the blood vessels and lymphatic vessels. So, does it mean that the cancer cells have metastasized when they go out? Not necessarily. Our body still has a very strong immunity 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 body eventually. Then what happens when metastasis occurs? When a cancer cell goes out, it stays in a place and takes root, just like a mobile account settles in a foreign country, it can take root, then it may multiply and metastasize. So, what can we imagine? In terms of blood vessel shape, it can stay down the place must be very rich in blood vessels, and the vascular network is particularly large. Has anyone heard of aortic metastasis in this patient? No. Like the tunnel, the sludge in the large vessels, it is not easy to survive. 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 vessels and 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 accumulates next 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’m still holding it here! The lymph nodes have an input lymphatic duct and an output lymphatic duct. The lymph in this area is very thin, and it is possible for the tumor cells to enter and stay in the lymph nodes. 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, if you have breast cancer, you should check whether the lymph in the armpit is big or not. If this lymph node is big, it is likely to have been occupied by it. After occupying a bunker, it still has extended positions and runs forward to the second, third and fourth lymph nodes. This is the second route. Some people ask, the tumor is so small, why does the surgery have to be so big? Here is the reasoning. For example, if we take intestinal cancer as an example, we usually have to remove three stations of lymph nodes, and it is safer. If the metastasis is cut there, the safety factor is smaller. In fact, it is very difficult to figure out precisely where the lymph nodes have metastasized or whether they have metastasized, so it is often better to operate on the left than the right. In case there is a leak, the consequences are very dangerous. That’s why it’s important to cut more widely. The reason is that it is not a big obstacle to the human body to cut away a little bit more of the mesentery, and the reason is that the tumor is small but big. This is also the reason for the so-called radical surgery. It is safer to remove the whole thing along with the lymph nodes that may metastasize. Some people say that tumor should not be squeezed, touched or pressed, otherwise it will encourage it to metastasize, and this is also the reason. External pressure can make the tumor cells fall off and most of them will be destroyed, while a small part of them will be metastasized. However, we should not be afraid, not all of the tumor cells that are in the blood may metastasize. A significant portion of tumor patients can be found to have tumor cells in blood tests, but the vast majority of them do not metastasize. Secondly, “land army”. It is when the tumor infiltrates around and spreads directly over. For example, stomach and liver are adjacent to each other, when stomach cancer infiltrates outward, it can pass through the stomach wall and invade to the liver, causing liver metastasis. Generally speaking, direct invasion of 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. The third kind is airborne. How to talk about airborne? Let’s take gastric cancer as an example. Gastric cancer gradually develops from the mucosa to the submucosa, then to the muscle layer, then to the plasma membrane, to the 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.