What is secondary liver cancer

Secondary liver cancer is also called metastatic liver cancer. Malignant tumors in various parts of the human body can be transferred to the liver through the blood or lymphatic system. Tumors in adjacent organs can directly infiltrate the liver and form secondary liver cancer. In this case, the liver is often an innocent victim. It has nothing wrong with itself, but is affected by other tumors. The livers of patients with primary liver cancer are mostly based on hepatitis or cirrhosis, and liver cancer is just the result of long-term liver disease. The presence of liver metastasis means the spread of the primary tumor, which is a dangerous signal, but the progress of modern science and technology has changed this situation.

1. Causes and classification

1. How do cancer cells metastasize to the liver?

Cancer cells mainly invade the liver through the blood circulation system. The liver is an organ with a large blood flow, and there are two systems in the human body that supply blood to the liver. One is the portal vein system. The venous blood of all organs in the abdominal cavity, including the stomach, small intestine, colorectum, pancreas, and spleen, must be collected in the portal vein and then returned to the liver, sending the absorbed nutrients to the liver to synthesize various substances necessary for the human body, and detoxifying the toxins produced by human metabolism by the liver. At the same time, the primary malignant tumor cells of these organs can also flow directly to the liver through this pathway, and then stay in the liver to form metastatic tumors. The second blood supply system of the liver is the hepatic artery system. The fresh blood rich in oxygen supplied from the heart flows into the liver through the aorta, celiac trunk artery, common hepatic artery, and proper hepatic artery. Primary malignant tumor cells in organs outside the abdominal cavity, such as the lungs, breasts, kidneys, ovaries, etc., generally return to the heart and then metastasize to the liver through the arterial system.

In addition, organs such as the gallbladder, stomach, adrenal glands, and bile ducts are close to the liver and have a close relationship with it. However, when their primary malignant tumors grow to a certain size, they can easily spread directly to their "old neighbor" the liver, forming the so-called infiltration metastasis.

2. How do cancer cells form metastases in the liver?

When a malignant tumor grows to a diameter greater than 2 cm, it can release a large number of cancer cells into the blood circulation every day. These cancer cells can eventually reach the liver by "going with the flow". The liver's structure is like a thick sponge soaked in blood. The blood perfusion volume is large but the flow rate is slow. Tumor cells can easily enter the liver substance and stay there. Among them, the more malignant tumor cells that reach the liver can secrete certain growth factors to promote the proliferation of their own tumor cells and stimulate the growth of new capillaries around them, thus gradually forming independent tumor cell clusters. It will not take long for tumor metastasis lesions of a size visible to the naked eye to form.

2. Symptoms and hazards

Generally speaking, the clinical manifestations of secondary liver cancer are often mild, and the course of the disease is relatively hidden. When the number of tumors is small and the size is not large, secondary liver cancer often presents with symptoms caused by primary tumors of other organs, such as blood in the stool, weight loss, abdominal distension, and intestinal obstruction in colorectal cancer, jaundice, abdominal pain or back pain in pancreatic cancer, breast lumps in breast cancer, abdominal pain and black stools in gastric cancer, cough, hemoptysis, chest pain in lung cancer, etc. However, as the metastatic lesions in the liver gradually grow larger, patients may also experience symptoms similar to primary liver cancer, such as weight loss, fatigue, pain in the liver area, lumps in the liver area, and even ascites and jaundice. In rare cases, some highly malignant extrahepatic tumors may not be large in size and have no obvious symptoms, but they may have diffuse metastasis to the liver, with obvious enlargement of the liver and fullness in the liver area, which is sometimes difficult to distinguish from primary liver cancer.

3. Auxiliary examination and diagnosis

(I) Auxiliary examination

1. Most patients have no obvious liver symptoms, and liver metastases are often discovered during routine abdominal examinations after tumors in other parts of the body are discovered. Or, extrahepatic malignancies have been surgically removed, and patients are found to have liver metastases during regular outpatient checkups every few months. The main means of examination are abdominal color Doppler ultrasound, enhanced CT or magnetic resonance imaging, especially the latter two, which can directly detect liver masses and determine the number and size of metastatic tumors.

2. The physical examination may not reveal any specific findings, unless there are many large metastases, in which case the doctor may feel an enlarged liver and tenderness in the liver area.

3. Sometimes, because it is impossible to determine the nature of the liver tumor, or because there is suspicion of the presence of metastases in other parts of the body, or in order to find hidden primary malignant tumors that cause metastatic liver cancer, PET-CT can be performed for a whole-body scan.

4. In order to understand the function of the liver and provide necessary data for possible liver surgery, routine blood, urine and stool tests, coagulation function, and liver function tests (mainly bilirubin, albumin, and transaminase) should be performed. In order to differentiate from primary liver cancer, virological tests for alpha-fetoprotein, hepatitis B or hepatitis C are also necessary.