Cancer: Definition, Types, Stages, & Examples

  • Post last modified:September 29, 2021
  • Reading time:8 mins read

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Cancer Definition

Cancer is defined as malignant development caused by uncontrolled cell division in biology. It’s now a catch-all phrase for more than a hundred illnesses characterised by unregulated, aberrant cell proliferation. The cells spread (metastasis) to other areas of the body at advanced stages, either locally or through the bloodstream and lymphatic system.

The earliest historical mention of this ailment occurred in the context of breast cancer. Cancer is derived from the Ancient Greek καρκίνoς (karkínos), which means “crab,” since cancer cells “grip on and won’t let go” like crabs. Neoplasia, growth, and malignancy are synonyms.

Cancer vs Tumor

Cancers and tumours are similar in that both are characterised by aberrant cell division that results in the development of a mass of cells that serve no purpose. Tumors (also known as neoplasms) are a broader word for any abnormal cell proliferation. As a result, cancer might be classified as a form of tumour.

A malignant tumour is one that has the ability to develop and spread to other tissues indefinitely. Other characteristics of malignancies include the formation of new blood arteries on the afflicted tissue, the avoidance of planned cell death, and the ability to divide cells indefinitely.

Main Causes of Cancer

Cancer is not genetic, which means that a cancer-stricken parent will not pass the disease on to their children. The propensity to the disease, on the other hand, is handed on. Because the offspring inherits the parents’ faulty genes, they are at danger of acquiring cancer. A faulty gene might be the result of a sequence or collection of mutations that caused the gene to become aberrant.

Cancer, Cancer Definition, Cancer Stages, 1

Oncogenes, for example, are genes that were originally normal genes (proto-oncogenes) that performed their functions, such as cell development and proliferation, but have mutated into genes that can cause normal cells to become cancerous. These genes can be handed down to the next generation if they are present in the egg cell or sperm cell.

As a result, cancer caused by inherited altered genes is referred to as hereditary cancer. However, as previously said, cancer is not inherited, but the faulty gene that causes cancer is. When oncogenes are turned on, previously healthy cells escape apoptosis (programmed cell death) and instead multiply.

Only about 5% to 10% of all cancers are caused by genetic abnormalities passed down from parents.This indicates that most cancers are caused by altered genes in an individual’s genes.

The mutation is acquired later in life in this situation, therefore it is not inherited from the parents. One of them is carcinogen exposure. Physical, chemical, or biological carcinogens exist. They have the ability to wreak havoc on DNA. When genes are damaged by DNA, a problem emerges.

A mutation can occur when the nucleotide sequence of DNA is disturbed. Not all mutations result in noticeable alterations. When they occur, and the body’s inherent DNA repair systems fail to fix them, the mutation will remain and is likely to become heritable.

When this happens, normal protein synthesis may be disrupted, or the proteins may be produced but prove to be defective. In certain cases, the genes are active for longer periods of time than they should be.

Asbestos, tobacco smoke components, aflatoxin, and arsenic are examples of chemical carcinogens. Some infections have the ability to turn a cell malignant. Helicobacter pylori, hepatitis B or C virus, Epstein-Barr virus, HIV, and human papillomavirus all have the ability to change the host cell’s genes.

As a result, these infections might be biological carcinogens. Electromagnetic radiation, such as UV and ionising radiation, are examples of physical carcinogens. Since the late 1800s, electromagnetic pollution (dirty power) has been a problem.

Utility power, switch-mode power energy supplies in electronics, variable speed motors in “smart appliances,” PV system invertors, and utility ground current are all examples of it.

Cancer is caused by the interaction of genes with various carcinogens. Other risk factors, however, are also in play. The age of a person is a significant determinant in the development of cancer. The danger grows as the person gets older.

The underlying cause is thought to be the degradation of the body’s repair system as it matures. Aside from age, additional risk factors include lifestyle (e.g., smoking, excessive alcohol use, lack of exercise, and a poor diet) and environmental variables (e.g. pollution).

How Does Cancer Start?

Cancer is thought to develop as a result of a series of mutations. Multiple oncogenes, as well as altered tumour suppressor genes, are frequently implicated. The tumour suppressor gene’s biological function is critical in preventing tumours and malignancies from developing.

It controls cell division, corrects DNA mistakes, and triggers apoptosis when the time comes. As a result, when tumour suppressor genes change and are not repaired, they are unable to operate properly. As a result, the cell will be unable to divide under its own control. As the cells multiply, a tumour develops that has the potential to become malignant.

Are All Cancers Malignant?

Tumors aren’t always cancerous. Benign tumours are those that aren’t cancerous. Malignant tumours, on the other hand, are malignancies. Clinical stages are used to categorise cancers depending on their size and degree of metastasis.

Medical physicians do physical exams and testing, such as blood tests, imaging scans (e.g., MRI, CT scan, and ultrasound), and biopsy, to identify the clinical stage of cancer. The phases of cancer are as follows:

1. Stage 0 (Carcinoma in situ): aberrant cells exist but are not yet malignant.

2. Stage I (Early-stage cancer): cancer found in a single tiny region.

3. Stages II and III: cancer has spread to neighboring tissues or lymph nodes; some cancer cells have left the initial site and invaded neighboring tissues.

4. Stage IV (Advanced or Metastatic cancer): the disease has spread throughout the body.

Cancer Progression

There are about a hundred different kinds of cancer in humans. Lung cancer, breast cancer, bone cancer, colorectal cancer, prostate cancer, skin cancer, brain cancer, and stomach cancer are only a few of these diseases. All of them are the result of unrepaired genetic alterations that have accumulated over time.

Oncogenes and tumour suppressor genes that have been mutated or inactivated are genetic factors. A cell with such defective genes tends to divide uncontrollably and, more importantly, to avoid death.

As more of these cells with aberrant genes divide, a lump forms on the spot that serves no purpose other than to proliferate and invade other tissues. Some cells separate from the tumour and spread to different parts of the body. This is a sign of metastasis. Metastatic tumours cause the majority of cancer-related deaths.

New tumours take hold quickly in a variety of places. They grow new blood vessels and acquire access to the nutrients in the circulation as a result. Tumors that have no specific purpose might disrupt the regular functioning of the organ in which they are found.

The presence of malignant tumours in the lungs decreases the lungs’ air capacity in lung cancer. As a result, lung cancer sufferers have trouble breathing. The pathophysiology of cancer is depicted in the infographic on the right.

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