What is Cancer ?
Human body is made up of trillions of cells. Usually, human cells grow and make more cells when the body needs them. This happens through cell division. When cells get old or get hurt, they die, and new cells come in their spot.
Sometimes, this orderly process breaks down, and abnormal or damaged cells grow and multiply uncontrollably and spread to other parts of the body. This phenomenon is referred to as Cancer.
Cancer can develop anywhere in the human body. Cancerous cells can aggregate to form tumors, which are abnormal tissue growths. These tumors can either be cancerous (malignant) or non-cancerous (benign).
Malignant tumors infiltrate nearby tissues and can metastasize to distant sites, forming new tumors. Blood cancers like leukemias typically don’t form solid tumors.
Benign tumors do not invade neighboring tissues and are generally not harmful. They often do not recur after removal, unlike cancerous tumors which may reappear.
Despite being non-cancerous, benign tumors can grow large and cause severe symptoms, especially if they occur in critical organs like the brain.
What are the differences between Cancer Cells and Normal Cells?
- Cancer cells grow in the absence of signals telling them to grow where as Normal cells only grow when they receive such signals.
- Cancer cells ignore signals that normally tell cells to stop dividing or to die this process is known as programmed cell death, or apoptosis.
- Cancer cells invade into nearby areas and spread to other areas of the body. Normal cells stop growing when they encounter other cells, and most normal cells do not move around the body.
- Cancer cells tell blood vessels to grow toward tumors. These blood vessels supply tumors with oxygen and nutrients and remove waste products from tumors.
- Cancer cells hide from the immune system. The immune system normally eliminates damaged or abnormal cells.
- Cancer cells trick the immune system into helping cancer cells stay alive and grow. For instance, some cancer cells convince immune cells to protect the tumor instead of attacking it.
- Cancer cells accumulate multiple changes in their chromosomes, such as duplications and deletions of chromosome parts. Some cancer cells have double the normal number of chromosomes.
- Cancer cells rely on different kinds of nutrients than normal cells. In addition, some cancer cells make energy from nutrients in a different way than most normal cells. This lets cancer cells grow more quickly.
How Does Cancer Develop?
Cancer is a genetic disease; it is caused by changes to genes that control the way our cells function, especially how they grow and divide.
Genetic changes that cause cancer can happen because of:
- Errors that occur as cells divide.
- Damage to DNA caused by harmful substances in the environment, such as the chemicals in tobacco smoke and ultraviolet rays from the sun.
- Inherited from their parents.
Normally, the body gets rid of cells with damaged DNA before they become cancerous. However, as we get older, the body’s ability to do this decreases. This is why there’s a greater chance of getting cancer as we age.
Each person’s cancer has a unique combination of genetic changes. As the cancer continues to grow, additional changes will occur. Even within the same tumor, different cells may have different genetic changes.
What Are Different Types Of Cancers ?
Cancer encompasses over 100 distinct types, each typically designated by the specific organs or tissues where they originate. For instance, hepatocellular carcinoma originates in the liver, while ductal carcinoma arises in the breast tissue. Additionally, cancers may be categorized based on the histological type of the cells involved, such as epithelial cells or squamous cells.
Here are some categories of cancers that begin in specific types of cells:
Carcinoma: Carcinomas are the most common type of cancer. They are formed by epithelial cells, which are the cells that cover the inside and outside surfaces of the body. There are many types of epithelial cells, which often have a column-like shape when viewed under a microscope.
- Adenocarcinoma is a cancer that forms in epithelial cells that produce fluids or mucus. Most cancers of the breast, colon, and prostate are adenocarcinomas.
- Basal Cell Carcinoma is a cancer that begins in the lower or basal (base) layer of the epidermis, which is a person’s outer layer of skin.
- Squamous Cell Carcinoma is a cancer that forms in epithelial cells that lie just beneath the outer surface of the skin. Squamous cells also line many other organs, including the stomach, intestines, lungs, bladder, and kidneys. Squamous cell carcinomas are sometimes called epidermoid carcinomas.
- Transitional Cell Carcinoma is a cancer that forms in a type of epithelial tissue called transitional epithelium, or urothelium. This tissue, which is made up of many layers of epithelial cells that can get bigger and smaller, is found in the linings of the bladder, ureters, and part of the kidneys (renal pelvis), and a few other organs. Some cancers of the bladder, ureters, and kidneys are transitional cell carcinomas.
Sarcoma: Sarcomas are cancers that form in bone and soft tissues, including muscle, fat, blood vessels, lymph vessels, and fibrous tissue such as tendons and ligaments.
Osteosarcoma is the most common cancer of bone. The most common types of soft tissue sarcoma are Leiomyosarcoma, Kaposi Sarcoma, malignant fibrous histiocytoma, Liposarcoma, and Dermatofibrosarcoma protuberans.
Leukemia: Cancers that begin in the blood-forming tissue of the bone marrow are called leukemias. These cancers do not form solid tumors. Instead, large numbers of abnormal white blood cells build up in the blood and bone marrow, crowding out normal blood cells. The low level of normal blood cells can make it harder for the body to get oxygen to its tissues, control bleeding, or fight infections.
There are four common types of leukemia, which are grouped based on how quickly the disease gets worse [acute or chronic] and on the type of blood cell the cancer starts in [lymphoblastic or myeloid]. Acute forms of leukemia grow quickly and chronic forms grow more slowly.
Lymphoma: Lymphoma is cancer that begins in lymphocytes (T cells or B cells). These are disease-fighting white blood cells that are part of the immune system. In lymphoma, abnormal lymphocytes build up in lymph nodes and lymph vessels, as well as in other organs of the body.
There are two main types of lymphoma:
- Hodgkin lymphoma – People with this disease have abnormal lymphocytes that are called Reed-Sternberg cells. These cells usually form from B cells.
- Non-Hodgkin lymphoma – This is a large group of cancers that start in lymphocytes. The cancers can grow quickly or slowly and can form from B cells or T cells.
Multiple Myeloma: Multiple myeloma is cancer that begins in plasma cells, another type of immune cell. The abnormal plasma cells, called myeloma cells, build up in the bone marrow and form tumors in bones all through the body. Multiple myeloma is also called plasma cell myeloma and Kahler disease
Melanoma: Melanoma is cancer that begins in cells that become melanocytes, which are specialized cells that make melanin (the pigment that gives skin its color). Most melanomas form on the skin, but melanomas can also form in other pigmented tissues, such as the eye.
Brain and Spinal Cord Tumors: There are different types of brain and spinal cord tumors. These tumors are named based on the type of cell in which they formed and where the tumor first formed in the central nervous system.
Other Types of Tumors:
- Germ Cell Tumors are a type of tumor that begins in the cells that give rise to sperm or eggs. These tumors can occur almost anywhere in the body and can be either benign or malignant.
- Neuroendocrine Tumors form cells that release hormones into the blood in response to a signal from the nervous system. These tumors, which may make higher-than-normal amounts of hormones, can cause many different symptoms. Neuroendocrine tumors may be benign or malignant.
- Carcinoid Tumors are a type of neuroendocrine tumor. They are slow-growing tumors that are usually found in the gastrointestinal system, most often in the rectum and small intestine. Carcinoid tumors may spread to the liver or other sites in the body, and they may secrete substances such as serotonin or prostaglandins, causing carcinoid syndrome.
