Cancer is one of the most dreaded diseases of the world. Cancer is the major cause of death around the globe. More than a million Indians suffer from cancer, and many of them die from it annually. According to the National Cancer Control programme- there are nearly 2.5 million patients with cancer in India. Changes or mutations in the DNA of cells are the cause of cancer. Each gene in a cell has a collection of instructions that teach the cell what functions to execute as well as how to grow and divide.

Errors in the instructions can cause a cell to stop functioning normally and even cause it to become cancerous. Hence, it becomes more important for us to have all the basic information about the disease. Let us learn what cancer is, its causes, its symptoms, and the diagnosis and treatment used to cure and prevent cancer. Continue reading to know more.

What is Cancer?

Cancer is defined as an unwanted and uncontrolled proliferation of cells without any differentiation. Cancer is a group of more than 100 different diseases that develop over time and involve the uncontrolled division of the body’s cells. It involves malignant growth or tissue enlargement due to unlimited and uncontrolled mitotic division of specific cells and invades surrounding tissues, forming tumours. In simple terms, healthy cells are programmed to “know what to do and when to do it”, but cancer cells do not know this programming, and hence they grow and replicate out of control. They also serve no physiological function. These cells are now termed neoplasm.

Fig: Normal and Abnormal Cell Growth

Cancer Cells

Cancer cells are cells that grow out of control. Cancer cells ignore signals to stop dividing and grow uncontrollably, unlike normal cells. They cannot recognise their natural boundary, and as a result, they may spread to areas of the body where they do not belong. Continuous division of cancerous cells gives rise to masses of cells called tumours. Following are some differences between cancer cells and normal cells:

Normal Cells	Cancer Cells
1. Mortal (die after \( \sim 50\) divisions)	Immortal (divide indefinitely)
2. Contact inhibition	Loss of contact inhibition
3. Stay bound together	Can easily detach from each other
4. Controlled cell death (apoptosis)	Unresponsive to apoptosis
5. Controlled cell division	Increased rate of cell division
6. Control of angiogenesis	Unregulated angiogenesis
7. Mature into functional cells	Do not mature into functional cells

Learn Everything About Infectious Diseases Here

Tumours can be classified into three categories as follows:
1. Benign Tumours or Non-Cancerous Tumours
2. Malignant Tumours or Cancerous Tumours
3. Premalignant Tumours

1. Benign Tumours or Non-Cancerous Tumours: Benign tumours are made up of non-cancerous cells, so they cannot invade nearby cells. It is relatively harmless as compared to malignant tumours. It usually grows slowly and causes minor damage to the body. However, if benign tumours occur in areas such as the brain, it can be fatal. The treatment of it requires surgery, and it does not grow back. Adenomas, fibroids, hemangiomas and lipomas are examples of Benign tumours.

2. Malignant Tumours or Cancerous Tumours: Malignant tumours are made up of cancerous cells that invade nearby tissues. It can move into the bloodstream or lymph nodes, spreading to other tissues within the body. This is called metastasis. It usually multiplies. This is very serious and may cause the death of the patient. Carcinoma, sarcoma, germ cell tumour, and blastoma are examples of Malignant tumours.

3. Premalignant Tumours: Premalignant tumours are observed to have the characteristics of malignant tumours. It may not have metastasised yet, but it has the potential to turn into cancerous cells. In simple words, a premalignant tumour is a type of tumour that has an increased risk of becoming cancer. Actinic keratosis, cervical dysplasia, metaplasia of the lung, and leukoplakia are examples of premalignant tumours.

Fig: Benign Cells and Malignant Cells

Types of Cancer

There are more than hundreds of types of cancer-based on the abnormal cell growth of a particular part of the body’s organ. Major six categories are listed below:

1. Carcinoma: Carcinoma, also called the cancer of the internal or external lining of the body, is the most common type. It originates from epithelial cells of the body. These are diagnosed mostly in breasts, skin, pancreas, lungs, and other organs and glands. Carcinomas are divided into two subtypes:

a. Adenocarcinoma- It develops in an organ or a gland.

b. Squamous cell carcinoma- It originates in the squamous epithelium.

2. Sarcoma: It refers to cancer that occurs in supportive and connective tissues like bones, tendons, cartilages, muscles, and fats. The most common form of sarcoma in the bone is osteosarcoma or osteogenic sarcoma, and in soft tissues include Kaposi sarcoma, liposarcoma (adipose tissue), leiomyosarcoma (smooth muscles), etc.

3. Myeloma: It is the type of cancer that originates in the plasma cells of bone marrow. The plasma cells produce proteins found in the blood. Multiple Myeloma is also known as Kahler disease.

4. Leukaemia: It is also called liquid blood cancer. The word ‘Leukemia’ means ‘white blood’ in Greek. It is a cancer of bone marrow. It is often associated with the overproduction of immature white blood cells (WBCs). These WBCs do not perform well as they should. Therefore the patient is often prone to infection. Leukaemia also affects red blood cells (RBCs) and can cause poor blood clotting and fatigue due to anaemia.

5. Lymphoma: It is the type of cancer that develops in the glands or nodes of the lymphatic system, which are a part of our immune system. Lymphomas may also occur in specific organs like the stomach, breast, or brain. These lymphomas are called extranodal lymphomas. There are two subtypes of lymphomas:

a. Hodgkin lymphoma –It originates in the B cells

b. Non-Hodgkin lymphoma – It originates in B or T cells

6. Mixed Types: The components may be within one category or from different categories in the mixed type of cancers. Some of the examples of this are given below:

a. Carcinosarcoma

b. Teratocarcinoma

c. Adenosquamous carcinoma

d. Mixed mesodermal tumour

Fig: Types of Cancer

Symptoms

Prevention is always better than cure. Thus, it is always better to detect disease by its symptoms than cure it after suffering. Following are some of the symptoms of cancer. Noticing any of the following symptoms does not mean that one has cancer. But to be safe, one needs to consult a doctor about the symptoms and signs.

1. Unexpected weight loss: A loss of 10 or fewer pounds or more could be nothing to worry about. However, this may be the first sign of cancer in a few rare cases.

2. Fatigue:  Extreme fatigue that does not improve with rest may be an early sign of cancer. Cancerous cells use all your body’s nutrients to grow rapidly; hence those nutrients no longer replenish the body. As a result, one may feel extremely tired.

3. Fever: Fever is a common symptom of many other diseases. But a fever that happens mostly at night has no longer symptoms of any other infection; experiencing night sweats may be a symptom of cancer.

4. Pain: Pain is also a common symptom of many other diseases. But if a person is suffering from pain that does not go away and is not sure where the pain is coming from, he should contact your doctor.

5. Persistent lump or thickening in tissues is another cancer symptom, especially in the tongue, breast, and uterus.

6. Bleeding or discharge: Any irregular bleeding or blood-tinged discharge from any body opening.

7. Any sore that does not heal quickly.

8. Any new change in the form of moles or warts.

9. Continuous hoarseness in voice, coughing, or difficulty swallowing something.

Fig: Signs and Symptoms of Cancer

Causes of Cancer

Following are some of the most common causes that lead to cancer.

1. Transformation of normal cells into cancerous neoplastic cells or cancerous cells may be induced by physical, chemical, or biological agents. These agents are called carcinogens.

2. Ionising radiations like X-rays and gamma rays and non-ionising radiations like UV cause DNA damage, leading to neoplastic transformation, i.e. formation of cancerous cells.

3. Occupational and Environmental Factors such as exposure to nickel, asbestos, chromate, and radioactive substances are also some of the causes of cancer.

4. Social and Psychological factors like stress and increased negative emotions.

5. Various chemicals in food like sodium nitrate and Clostridium botulism also cause cancer.

6. The chemical carcinogens present in tobacco smoke are a major cause of lung cancer.

7. Cancer-causing viruses called oncogenic viruses have genes called viral oncogenes. Furthermore, many genes are known as cellular oncogenes (c-onc), or proto-oncogenes. These cells are identified in normal cells that may lead to oncogenic transformation when activated under some conditions.

Fig: Causes of Cancer

Diagnosis

Early detection and diagnosis of cancer are very important before it spreads to other parts of the body. Also, it allows the disease to be treated successfully in many cases. There are several methods of diagnosing cancer with advantages in technology. Following are some of the major diagnosis methods:

Method	Description
Radiological diagnosis	It includes X-ray, MRI (Magnetic Resonance Imaging), ultrasound and CT (Computed Tomography) scan, etc. These are one of the best early, non-invasive methods of cancer diagnosis.
Cytological diagnosis	It includes FNAC (Fine Needle Aspiration Cytology). FNAC is a popular method of tumour diagnosis, particularly for lymph nodal tumours, breasts tumours, salivary glands tumours, thyroid tumours, etc.
Histological diagnosis	For histological diagnosis of cancer, a biopsy is used as a method of sampling. In this method, a piece of the suspected tissue is cut into thin sections, stained, and examined under a microscope by a pathologist.
Frozen section	It is a quick diagnosis method. In this method, the tissue is quickly frozen at around 200 C in the frozen section, immediately sectioned and stained. The whole process from receiving, staining to the diagnosis of tissue can be completed within 10 to 15 days.
Haematological diagnosis	In this method, the marrow is aspirated by the bone marrow. It is used for the diagnosis of Leukemia.
Immunohistochemistry	In this method, antibodies against cancer-specific antigens are used for the detection of certain cancers.
Molecular Diagnosis	Molecular diagnosis is an emerging field. These are useful in the detection of minute translocation and minimal residual disease.
Tumour Marker	Some tumours release substances called tumour markers. Blood tests can be performed to detect these tumour markers. Tumour markers are the biochemical indicators of a tumour which may be antigens, cytoplasmic proteins, enzymes, hormones, etc.

Treatment of Cancer

The type of treatment depends upon the type of cancer the patient has. Some patients have only one treatment. But most of the patients have a combination of treatments depending upon the complication of the disease. Some of the cancer treatment options are given below:

1. Radiotherapy is a type of cancer treatment that uses high doses of radiation to kill cancer cells and shrink tumours by damaging their DNA. Cancer cells whose DNA is damaged stop dividing or die. Dead damaged cells are broken down and removed by the body.

2. Chemotherapy treatment type that uses drugs to kill cancer cells. Chemotherapy works by slowing or stopping the growth of the cells. Most of these chemotherapeutic drugs have side effects like hair loss, anaemia, etc.

3. Immunotherapy: It is a type of biological therapy. This therapy helps the immune system to fight against cancer. The positive patients are given substances known as biological response modifiers such as α-interferon that activate their immune system and help to destroy the tumour.

4. Hormone therapy: It is a type of cancer treatment that slows or stops the growth of breast and prostate cancer that uses hormones to grow. It is also called hormonal therapy.

5. Targeted therapy: This type of treatment targets the changes in cancer cells, which help them grow, divide and spread.

6. Bone marrow transplantation/Stem cells transplantation: It is a type of treatment that restores blood-forming stem cells in cancer patients who have had their cancer destroyed by a very high dosage of radiotherapy and chemotherapy.

7. Surgery: In this treatment, surgeons do surgery to remove cancer from the patient’s body. They often use small, thin knives known as scalpels and other sharp tools to cut the body during the surgery. Surgery often needs many cuts through skin, muscles, or sometimes even bone. These cuts can be very painful and take some time to recover after surgery.

Fig: Cancer Treatment

Summary

Cancer is the most dreaded disease in the world. It is one of the major causes of death all over the world. About 0.7 million new cases are diagnosed every year, and nearly half of them die. More than 60% to 70% of these cancer patients are between the age of 35-60 years. It is expected that with improved life expectancy, these cases will triple in number in the coming years. Cancer is the unwanted and uncontrolled growth of body cells.

There are different types of cancers such as carcinoma, sarcoma, myeloma, Leukemia, lymphoma, and mixed types such as Carcinosarcoma, Teratocarcinoma, Adenosquamous carcinoma, and Mixed mesodermal tumour, etc. Unexpected weight loss, fatigue, pain, fever, Persistent lump or thickening in tissues, bleeding or discharge from organs or tissues are some of the symptoms of cancer. The agent causing cancer is called carcinogens. There are various causes of cancer, such as social and psychological factors, occupational and industrial factors, etc. This can be diagnosed and detected using different methods such as radiological diagnosis, cytological diagnosis, histological diagnosis, etc. Cancer can be treated using different treatment methods such as radiotherapy, chemotherapy, surgery, hormonal therapy, immunotherapy, etc.

FAQs

Q.1. What is cancer? How does it occur?
Ans: Cancer is the unwanted and uncontrolled growth of body cells. When cells grow old or become damaged, they die, and new cells take their place. Sometimes this continuous process is disturbed, and abnormal or damaged cells grow and multiply when they shouldn’t. These cells may form tumours, which are lumps of tissue.

Q.2. What are the symptoms of cancer?
Ans: Unexpected weight loss, fatigue, pain, fever, persistent lump or thickening in tissues, bleeding, or discharge from organs or tissues are some of the symptoms of cancer.

Q.3. Write the difference between tumour and cancer.
Ans: Cancer is a disease where cells start to divide uncontrollably, almost anywhere in the body. On the other hand, a tumour is when this uncontrolled growth occurs in solid tissue such as an organ, muscle, or bone.

Q.4. What is the first sign of cancer?             
Ans: Unexpected weight loss of 10 pounds or more may be one of the first signs of cancer.

Q.5. What are the types of cancer?  
Ans: There are different types of cancers such as carcinoma, sarcoma, myeloma, Leukemia, lymphoma, and mixed types of cancers such as Carcinosarcoma, Teratocarcinoma, Adenosquamous carcinoma, and Mixed mesodermal tumour, etc.