Release date:2020/11/27 8:11:52
What is cancer? For this question, many people may have little knowledge, and the answers given are various, such as cancer is tumor, cancer is malignant tumor, cancer is leukemia and so on.
With little knowledge of cancer, many people either talk about cancer with unnecessary panic, or delay their illness due to their neglect. So what exactly is cancer? What is the difference between cancer cells and normal cells? What are the types of cancer?
What is cancer?

Cancer is not a kind of disease, but a name for a group of related diseases. In all types of cancer, some cells of the body begin to divide continuously and spread to surrounding tissues.
Cancer can occur in almost any part of the body. The human body is composed of trillions of cells. Under normal circumstances, cells grow and divide to form new cells when the body needs them. When cells get older or damaged, they die, and new cells replace them.
However, when cancer occurs and develops, this orderly process collapses. As cells become more and more abnormal, older or damaged cells survive when they should die, new cells are formed when they are not needed. These abnormal cells can divide continuously and form tumors.
Many cancers form solid tumors, but for blood cancers, such as leukemia, they generally wouldn’t form solid tumors. Generally,
cancer mainly includes malignant tumors and blood cancers.
What is the difference between cancer cells and normal cells?
Cancer cells are different from normal cells in many ways, making their growth out of control and becoming aggressive.
One important difference is that cancer cells will divide continuously and are not "obedient". They will ignore the signals that the body sends under normal circumstances that "tell" cells to stop dividing or start programmed death or apoptosis. Normal cells listen to the "arrangement" of the signal and eliminate cells the body doesn’t need.
Cancer cells may also affect normal cells, molecules and blood vessels around the tumor. This area is often called the microenvironment. For example, cancer cells can induce normal cells near the tumor to form blood vessels, provide the tumor with oxygen and nutrients which needed for growth, and remove the useless substances from the tumor.
Cancer cells are also often able to evade attack by the immune system. The immune system is a network of organs, tissues and special cells that protect the body from infections and other diseases. Although the immune system normally removes damaged or abnormal cells from the body, some cancer cells can "hide" from being discovered by the immune system.
Tumors can stay alive and grow under the immune system. In some cases, cancer cells can even manipulate certain immune cells to help them metastasize, spread, and avoid attacks from the immune system.

cancer type
What are the types of cancer?
type of cancer is usually named according to the organ or tissue in which it originally formed. For example, lung cancer starts from lung cells, and brain cancer starts from brain cells. Cancers can also be described by the types of cells that form them, such as carcinoma, sarcoma, leukemia, lymphoma, and myeloma.
1. Carcinoma
Carcinoma, a malignant tumor that starts in epithelial cells and is the most common type of malignant tumor. Epithelial cells cover the internal and external surfaces of the body, such as cells in the skin, digestive organs, chest cavity, and abdominal cavity.
There are different types of epithelial cells that can develop into different types of cancer, including squamous cell carcinoma, adenocarcinoma (most breast cancers, colorectal cancers, and prostate cancers are adenocarcinomas), transitional cell carcinoma, and basal cell carcinoma.
2. Sarcoma
Sarcomas are cancers that form in bones and soft tissues, including muscle, fat, blood vessels, lymphatic vessels, and fibrous tissues (such as tendons and ligaments).
There are two main types of sarcoma: osteosarcoma and soft tissue sarcoma. Osteosarcoma originates from bone cells and is also the most common bone cancer; soft tissue sarcoma mainly includes chondrosarcoma originating from chondrocytes, and rhabdomyosarcoma or leiomyosarcoma originating from muscle cell carcinoma.
3. Leukemia
Leukemia is a type of cancer that originates in the hematopoietic tissue of the bone marrow, and is the most common type of cancer in children. It won’t form solid tumors. There are four common types of leukemia, which are usually grouped according to the speed of disease progression (acute or chronic) and the type of blood cells (lymphocytes or bone marrow) where the cancer started.
4. Lymphoma
Lymphoma is cancer that starts in lymphocytes (T cells or B cells). In lymphoma, abnormal lymphocytes accumulate in lymph nodes, lymph vessels and other organs of the body. There are two main types, Hodgkin's lymphoma and non-Hodgkin's lymphoma.
5. Multiple myeloma
Multiple myeloma is a cancer that starts in plasma cells (a type of immune cell). Plasma cells are white blood cells produced in the bone marrow that can produce antibodies (immunoglobulins) to help fight infection. When abnormal plasma cells accumulate in the bone marrow, tumors can form in the bones. Multiple myeloma is also called plasma cell myeloma and Kahler disease.
6. Melanoma

Melanoma is a malignant tumor that starts in melanocytes. Melanocytes are special cells that make melanin. Most melanomas form on the skin, but they can also form in other pigmented tissues, such as the eyes.
7. Brain and spinal cord tumors
Brain and spinal cord tumors are also called central nervous system tumors. There are many types of brain and spinal cord tumors, usually named according to the type of cell that the tumor forms and where it first formed in the central nervous system. For example, astrocytoma begins in astrocytes, called astrocytes. Brain tumors can be benign (not cancer) or malignant (cancer).
In addition, there are other types of cancers, such as germ cell tumors, neuroendocrine tumors, and carcinoids.
All in all, there are many types of cancer, and the number of cancer cases is increasing. Only with a clearer understanding of cancer can we better prevent and cope with cancer.

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What Is Cancer? 
[2] Cancer Basics. 
[3] The main types of cancer 

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