Cancer

What is cancer?

Cancer refers to any of a large number of diseases characterized by the production of uncontrollably dividing abnormal cells that are capable of infiltrating and killing normal body tissue. Cancer also has the potential to spread all over your body.

Cancer is the world’s second-leading cause of death. But for many cancer types, survival rates are improving, due to advances in cancer screening and cancer care.

Cancer definition

As per NCI’s dictionary of cancer terms cancer definition is :

“A term for diseases in which abnormal cells divide without control and can invade nearby tissues. Cancer cells can also spread to other parts of the body through the blood and lymph systems. There are several main types of cancer. Carcinoma is a cancer that begins in the skin or in tissues that line or cover internal organs. Sarcoma is a cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue. Leukemia is a cancer that begins in blood-forming tissue, such as the bone marrow, and causes too many abnormal blood cells to be made. Lymphoma and multiple myeloma are cancers that begin in the cells of the immune system. Central nervous system cancers are cancers that begin in the tissues of the brain and spinal cord. Also called malignancy”.

Cancer division, growth & metastasis

The trillions of cells it’s made of expand and divide in a healthy body, as the body needs them to work everyday. In a way that is determined by the type of cell, healthy cells have a particular life cycle, reproducing and dying off. When they die, new cells take the place of old or damaged cells. This mechanism is affected by cancer and contributes to excessive growth of cells. It’s caused by DNA modifications or mutations.

In the individual genes of every cell, DNA exists. It has instructions that tell the cell when to perform functions and how to expand and break. Mutations happen often in DNA, but these errors are normally resolved by cells. A cell may become cancerous when a mistake is not corrected.

Mutations can allow cells that need to be replaced to survive instead of die, and when they are not required, new cells can form. These extra cells will break uncontrollably, causing the development of tumors. Depending on where they develop in the body, tumors can cause a number of health problems.

But the tumors are not all cancerous. Benign tumors are noncancerous and do not spread to tissues in the vicinity. Often as they press against neighboring organs and tissue, they may develop large and cause issues. Malignant tumors are cancerous and are capable of invading other body sections.

Some cancer cells may spread to distant areas of the body via the bloodstream or lymphatic system as well. These types of cancers are called as metastatic cancer. It is considered that cancers that have metastasized are more advanced than those that have not. Metastatic cancers tend to be more difficult and fatal to treat.

Types of cancer

Cancers, even though they spread to other areas of the body, are named for the region in which they begin and the type of cell they are made of. A cancer that starts in the lungs and spreads to the liver, for example, is also called lung cancer. For some general cancer types, there are also some clinical terminology used:

• Carcinoma is a cancer that starts in the skin or the tissues that line other organs. Ex: prostate cancer, breast cancer, lung cancer, & colorectal cancer.
• Sarcoma is a cancer of connective tissues such as bones, muscles, cartilage, and blood vessels. Ex: bone cancer etc.
• Leukemia is a cancer of bone marrow, which creates blood cells. The 4 main types of leukemia are acute lymphocytic leukemia, chronic lymphocytic leukemia, acute myeloid leukemia, and chronic myeloid leukemia.
• Lymphoma and myeloma are cancers of the immune system. There are 2 main types of lymphomas: Hodgkin lymphoma and non-Hodgkin lymphoma.

How cancer spreads ?

The bloodstream or lymphatic system can carry cancer cells to other parts of the body as a cancerous tumor grows. The cancer cells are developing and can evolve into new tumors during this process. This is referred to as metastasis.

The lymph nodes are one of the first sites where cancer frequently spreads. Small bean-shaped organs that help battle infection are lymph nodes. They are found in clusters, such as the collar, groin area, and under the arms, in various parts of the body.

Cancer can spread to distant parts of the body via the bloodstream as well. The bones, liver, lungs, or brain may include these parts. And if the cancer spreads, the area where it started is still named for it. For instance, it is called metastatic breast cancer, not lung cancer, if breast cancer spreads to the lungs.

Signs & symptoms of cancer

Depending on what part of the body is affected, signs and symptoms caused by cancer can differ. Some general symptoms and signs associated with cancer, but not unique to it, include:

• Fatigue
• Lump or area of thickening that can be felt under the skin
• Weight changes, including unintended loss or gain
• Skin changes, such as yellowing, darkening or redness of the skin, sores that won’t heal, or changes to existing moles
• Changes in bowel or bladder habits
• Persistent cough or trouble breathing
• Difficulty swallowing
• Hoarseness
• Persistent indigestion or discomfort after eating
• Persistent, unexplained muscle or joint pain
• Persistent, unexplained fevers or night sweats
• Unexplained bleeding or bruising

How cancer cells differs from normal cells ?

The normal cells, molecules and blood vessels surrounding and feeding a tumor, a region known as the microenvironment, may be able to affect cancer cells. Cancer cells, for example, may cause nearby normal cells to form blood vessels that supply oxygen and nutrients to the tumors they need to develop. These blood vessels also extract tumor-derived waste products.

It is also always possible for cancer cells to evade the immune system, a network of organs, tissues, and specialized cells that defend the body from infections and other conditions. While damaged or dysfunctional cells are generally eliminated from the body by the immune system, some cancer cells are able to “hide” from the immune system.

In order to remain alive and develop, tumors can also use the immune system. For instance, cancer cells can actually keep the immune system from destroying cancer cells with the help of certain immune system cells that normally prevent a runaway immune response.

How cancer arises ?

Cancer is a genetic disease that is caused by genetic modifications that regulate the way our cells function, especially how they develop and divide.

From our ancestors, genetic variations that cause cancer can be inherited. During the lifetime of a human, they may also emerge as a result of mistakes that occur as cells divide or because of DNA damage caused by certain environmental exposures. Substances such as contaminants in cigarette smoke, and radiation such as ultraviolet rays from the sun provide cancer-causing environmental exposures. The cancer of each individual has a distinctive combination of genetic changes.

Additional changes will occur as the cancer continues to develop. Cancer cells in general have more genetic variations than normal cells, such as mutations in DNA.

Any of these modifications may have little to do with the disease; they may be the result of the disease, rather than its cause.

When cancer spreads ?

A cancer that has spread to another place in the body from the place where it first began is called metastatic cancer. Metastasis is called the mechanism by which cancer cells migrate to other areas of the body.

Metastatic cancer has the same name as the original, or primary, cancer and the same type of cancer cells. For instance, metastatic breast cancer, not lung cancer, is breast cancer that spreads to and forms a metastatic tumor in the lung.

Metastatic cancer cells normally appear the same as cells of the original cancer under a microscope. In addition, metastatic cancer cells and original cancer cells usually have certain molecular features in common, such as the presence of unique changes in chromosomes.

Treatment can help to extend the lives of some people with cancer that is metastatic. In general, however the primary objective of metastatic cancer therapies is to monitor the development or alleviate symptoms caused by cancer. Metastatic cancers may do significant harm to how the body functions, and metastatic disease causes the majority of people who die of cancer to die.

Treatment of cancer

There has been great advancement in the treatment of cancer and if detected early cancer can be fully cured. Mentioned below are some of the treatment options that are followed world over :

• Surgery
• Chemotherapy
• Radiation therapy
• Immunotherapy
• Targeted therapy
• Proton therapy
• CAR T Cell therapy

There are lot of other treatment methods under clinical trials and development phase at present like T Cell therapy, NK cell therapy etc.