Cancer – Causes, Symptoms, Types, Stages and More

The definition of cancer is an uncontrolled growth and spread of cancer cells. The disease is invasive, meaning it can invade surrounding tissue and can metastasize to distant organs from its original site.

Metastases are a significant cause of cancer deaths. Cancer can affect nearly any part of the body. (1) Currently, there are over 100 types of cancers. Some are avoidable.

For instance, avoiding sun exposure helps reduce the risk of skin cancer. Just as, smoking and tobacco use increases the risk of lung cancer. (2)

Cancer research has paved the way for many cancer cures like radiotherapy or chemotherapy and surgery.

However, there are deadly forms of the disease, and a healthy lifestyle and preventative measures like exercise are necessary to reduce the risks of the disease. (3) (4)

Cancer introduction

Globally, cancer is the second leading cause of death. Lifestyle influences the risks of the disease. (5)

For instance, one-third of deaths resulting from the disease result from five leading behavioral and dietary risks:

Deaths resulting from the disease are more significant in low- and middle-income countries. Tobacco accounts for 22 percent of cancer deaths. Much research is being performed on the causes and treatments of the disease.

For instance, current research on lung cancer includes the possible advantages of green tea’s anti-cancer effects on the lung. Epidemiological studies on humans and investigations in animal models suggest that consumption of green tea has anti-cancer effects. (6)

Limonene is another area of interest for cancer patients. Limonene stimulates the body’s antioxidant detoxification enzyme system, helping to stop the disease before it starts.

Oranges, lemons, mandarins, and limes contain high amounts of limonene in the peel. (7) (8)

What Lemon Water Does to Your Body?

Cancer is a disease that, when detected early, survival rates increase. (9) (10) Malignant tumors and neoplasms are also referred to as cancer.

Common cancer types

Both the National Cancer Institute and the American Cancer Society created the following list of cancer incidence and mortality of common cancers. (11)

The American Cancer Society defined common cancers as those with 40,000 cases or more.

  • Lung
  • Bladder
  • Melanoma
  • Breast
  • Non-Hodgkin Lymphoma
  • Pancreatic
  • Colon and Rectal
  • Endometrial
  • Prostate
  • Kidney
  • Liver
  • Leukemia
  • Thyroid

Deadliest cancer types

Cancer is characterized by abnormal cell growth. While there are successful treatments, some types of the disease are hard to combat.

Cancer cells may also lay dormant, hiding in the body for years, and then resurface. The following cancers are the deadliest cancer types.

  • Lung and bronchial
  • Breast
  • Colon and rectal
  • Pancreatic
  • Prostate
  • Leukemia
  • Non-Hodgkin lymphoma
  • Liver and intrahepatic bile duct
  • Breast
  • Ovarian
  • Esophageal

Cancer causes

Various factors contribute to or cause, cancer, and deaths from the disease. For instance, lack of exercise and an unhealthy diet contribute to a high-risk cancer lifestyle.

Occupational factors can cause cancers such as in the lung or lungs. Sun exposure increases the risk of skin cancer. (12) (13) (14)

Tobacco use is a leading cause of lung and throat cancer. (15) Genetics can play a role in some types of disease.

However, genetics and most cancers are not linked. Infections with some viruses, bacteria, and other germs can also increase certain types of cancer risks. (16) (17)

  • Unhealthy diet
  • Lack of exercise
  • Tobacco use
  • Occupational factors
  • Sun exposure
  • Infections
  • Genetics
  • Radiation
  • Chemicals

Cancer-causing infections

Since the 20th century, researchers have been studying the connection between infection and cancer in animals.

More to date, infections with certain viruses, bacteria, and parasites are risk factors for different types of disease in humans. (18)

Cancer-causing infections link to roughly 15 to 20 percent of cancers. Therefore, infections raise the risk of some types of disease.

  • Viruses can directly affect the genes of a cell. Genes inside cells are responsible for growth control. With some viruses, the virus may insert their genes into the cell, being accountable for cells to grow out of control.
  • Infections that cause long-term inflammation in a specific part of the body can affect the cells in the area. Also, at risk are nearby immune cells. The changes to the cells can lead to cancer. (19) (20)
  • Infections can also suppress the immune system. The immune system’s role is to help protect the body from some types of disease.

Cancer-causing infections like human papillomavirus and hepatitis are responsible for as much as 25 percent of cancer cases in low- and middle-income countries.

Cancer symptoms

Signs and symptoms of the disease vary depending on the part of the body that is affected. General symptoms associated with the disease include:

  • Fatigue
  • Weight changes
  • Lump or thickening of the area felt under the skin
  • Discoloration in skin changes like darkening, redness, or yellowing of the skin
  • Sores that don’t heal
  • Mole changes
  • Difficulty swallowing
  • Persistent cough or trouble breathing
  • Changes in bowel or bladder habits
  • Hoarseness
  • Persistent muscle or joint pain with no explanation
  • Persistent indigestion or discomfort after eating
  • Persistent fever or night sweats without reason
  • Unexplained bleeding or bruising

Cancer diagnosis

Microscopic examination helps determine the presence of the disease. Molecular and cytogenetic markers are, many times, used in the examination.

The techniques are effective in collecting additional information about the tumor. (21)

Samples of cells or tissue are examined under a microscope. Examination for further diagnosis includes tests on the cells’ proteins, DNA, and RNA to determine if cancer is present. Biopsies can be performed on lumps. (22)

A biopsy is the removal of a portion of the lump to be tested for cancer and infections or other growth causing problems that may mimic the disease.

Imaging tests and physical exams detect lumps. However, a sample is necessary to examine under a microscope to determine if they are cancerous. (23)

Cancer treatments

The treatment type will depend on the type and stage of the illness.

Most cancer patients have a combination of treatments like surgery and chemotherapy or radiation therapy. (24)


Depending on where the disease has developed in the body, as well as its type, surgical removal of the tumor may be the best option. (25)

Aside from the traditional, “under the knife,” surgery can also include cryosurgery, lasers, hyperthermia, and photodynamic therapy.

Surgery is a treatment for the removal of the entire tumor and to ease symptoms.

Radiation therapy

Radiation is administered to patients in high doses. The purpose of radiation therapy is to kill cancer cells and shrink tumors. (26) (27)

Types of radiation therapy include: (28)

  • External beam radiation therapy – A machine that aims radiation at cancer, sending radiation to the affected area from many directions
  • Internal radiation therapy – A solid or liquid radiation source is put inside the body.


With chemotherapy, drugs are used to kill cancer cells. Chemotherapy stops or slows cancer cells’ growth.

It is a treatment that can work to cure, lessen the chance of a return, or prevent the disease and its growth. It is also useful in easing symptoms associated with the disease.


Immunotherapy is a therapy that supports the immune system in the fight against the disease. Immunotherapy is a biological therapy, that uses substances made from living organisms to treat the condition. (29)

Targeted therapy

Targeted cancer therapies are drugs or other substances that block the growth and spread of cancer by interfering with specific molecules (“molecular targets”) that are involved in the growth, progression, and spread of cancer. Targeted cancer therapies are sometimes called “molecularly targeted drugs,” “molecularly targeted therapies,” “precision medicines,” or similar names. (30) (31) (32)

Hormone therapy

Hormone therapy slows or stops the growth of the disease in the breast or prostate. It is a treatment that is beneficial in lessening the chance of its return, as well as slowing growth. Patients also benefit as it helps to ease associated symptoms of the disease. (33)

Stem cell transplant

A stem cell transplant is used when a patient’s blood-forming stem cells have been destroyed due to high doses of chemotherapy or radiation therapy. Stem cell transplants are designed to restore blood-forming stem cells. The transplant grows different types of blood cells. (34) (35)

The primary type of blood cells restored include:

  • White blood cells
  • Red blood cells
  • Platelets

Precision medicine

Precision medicine includes genetics to help doctors determine the best treatment for their patients. (36)

Cancer stages

Various factors specific to the disease determine its stage. Most cancers are categorized in stages I to IV (one to four,), but some have stage zero. (37)

Stage I

Stage I cancers are, typically, small cancer or tumor that has not affected any other parts of the body, or the lymph nodes. They have yet to grow deeply into nearby tissues.

Stage II and stage III

With stage II and stage III cancers; nearby tissues are affected by the disease from its original site.  At this stage of the disease, lymph nodes may also become affected.

Stage IV

With stage IV cancer, the disease has spread to other parts of the body, or organs. This is a stage that is often referred to as advanced or metastatic cancer.

Cancer and diet

According to the UK Cancer Research site, healthier diets could prevent around one in 20 cancers. (38) Foods and nutrients have been shown to help prevent, or contribute, to certain types of disease.

According to the Harvard Health Organization site, less than 30 percent of an individual’s lifetime risk of developing the disease results from uncontrollable factors. In other words, individuals have the power to control much of their risks of the disease. (39)

A healthy diet is more than vitamins and nutrients; it is also maintaining a healthy weight and exercise. This thought is critical because obesity is the leading cause of 13 types of disease. A healthy diet to reduce the risks of the disease includes:

Diets high with:

  • Fruits and vegetables
  • Wholegrains
  • Healthy proteins

Diets low with:

  • High-calorie foods
  • Processed and red meat
  • Alcohol
  • Sugary drinks


Cancer is a disease that can affect nearly any part of the body. It is an invasive disease, meaning it can spread to surrounding tissue and can metastasize to distant organs from its original site.

Metastases are a significant cause of cancer deaths. Currently, there are over 100 types of cancer, some avoidable, some deadly. However, a healthy lifestyle, including diet and exercise, as well as preventative measures, reduces cancer risks.

Cancer causes include an unhealthy lifestyle, occupational factors, genetics, and infections. When cancer is suspected, samples of cells or tissues are examined to determine if it is present. If a suspicious lump or mole is suspected, a biopsy will likely be performed to determine if it is cancerous.

If cancer is diagnosed, cancer treatment will depend on the type and stage of cancer. Cancer stages are from one to four. Stage four is considered advanced as at this stage, it has spread to other parts of the body.

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