About Cancer
One of the deadliest diseases responsible for about 9.5 million lakh deaths in 2018, according to WHO, is cancer. Cancer is a term used to describe a large group of diseases that are characterized by cellular malfunction. Cancer is the deregulation of cell growth. In medical terms, cancer is known as malignant neoplasm; a broad group of diseases involving unregulated cell growth, and the unregulated cell growth forms a "tumour." Cancer can start anywhere in the human body which is made up of a trillion cells.
When cells become old or damaged they die and new cells take their place. But when cancer develops, this orderly process breaks down. Old and damaged cells survive when they should die and new cells form when they are not needed. These extra cells can divide without stopping and may form tumours.
How Does Cancer Develop?
Cancer is known to be a very dangerous genetic disease because it is caused by mutations in genes that control how our cells work, particularly how they divide and grow. So, errors that occur while cells divide can generate genetic alterations that cause cancer.
Chemicals and hazardous compounds in the environment, like chemicals in cigarette smoke and ultraviolet raysfrom the sun cause DNA damage that results in cancer. It can also be passed down to us from our parents as a genetic disease. Before the cells that have damaged DNA become malignant, they are eliminated by the body. But with growing age. the ability of the body to do so decreases. This is the reason why cancer is developed later in our life.
A unique set of genetic alterations are there in each person's cancer. As the malignancy progresses, additional alterations occur. Even within the same tumour, distinct cells may have diverse characteristics. Certain changes to genes cause cancer, the basic physical measure of inheritance.
Causes of Cancer
Carcinogens like chemicals, tobacco, alcohol, and radiations such as ultraviolet rays coming from the sun are considered the lead causes of cancer.
Types of Cancer
There are more than a hundred types of cancer. They are usually named for the organs or tissue where the cancer forms. Here are some categories of cancer.
Carcinoma
It is formed by epithelial cells, cells that cover the inside and outside surface of the body. Carcinoma in different epithelial cells has different names.
Sarcoma
These are the types of cancer that form in the bone and soft tissues including muscles, fat, lymph, cells, and fibrous tissue.
Melanoma
Melanoma cancer begins in the cell that begins with melanocytes. It is considered the most serious type of skin cancer. Melanoma occurs when the pigment cells, which give coloured skin become cancerous.
Diagnosis of Cancer
The earlier stage of diagnosis in cancer provides the best chance for cure. Doctors may use one or more following approaches to diagnose cancer.
Biopsy
Radiography technique
Computed tomography
Magnetic resonance imaging
Molecular biology techniques
Laboratory test
Physical exam
Treatment of Cancer
The type of treatment depends on the type of cancer and how advanced it is. Depending on cancer, a patient can have a combination of treatments such as:
Surgery
Chemotherapy
Radiation therapy
Immunotherapy
Targeted therapy
Many drugs have side effects in cancer patients like hair loss. So, interferons are injected into cancer patients to develop immunity against these side effects.
Types of Tumour
Based on their ability to undergo metastasis, tumours can either be cancerous or non-cancerous and are classified into three types:
Benign Tumour
This type of tumour is localized to a particular location in the body so it doesn't spread to the other body parts, and due to this reason, it is not that harmful. This tumour occurs in regions like the brain, and sometimes they turn fatal also. Surgery is one of the most common treatments to remove benign tumours.
Malignant Tumour
Malignant tumours are known to be cancerous, which shows that they tend to grow quickly to other tissues of the body. This tumour has high metastasis properties, and it grows frequently into the bloodstream, and from there it can form secondary tumours across different sites in the body part.
Premalignant Tumors
This tumour is a kind of benign tumour but it shows features of malignant tumours. This tumour has an increased risk of becoming cancer. Benign tumours become premalignant and eventually, malignant.
FAQs on Cancer
1. What is cancer as per the Class 12 Biology syllabus for 2025-26?
Cancer is a disease characterised by the abnormal and uncontrolled division of cells. These cells lose the property of contact inhibition, which normally stops cell growth upon contact with other cells. This results in the formation of cell masses called tumours.
2. What is the main difference between benign and malignant tumours?
The key difference lies in their ability to spread and cause harm.
- Benign tumours are non-cancerous. They remain confined to their original location, grow slowly, and typically do not spread to other parts of the body.
- Malignant tumours are cancerous and are made of neoplastic (tumour) cells. They grow rapidly, invade surrounding normal tissues, and can spread to distant sites through the blood or lymph to form new tumours.
3. Explain the concept of metastasis and its importance in cancer.
Metastasis is the most feared property of malignant tumours. It is the process by which cancer cells break away from the primary tumour, travel through the bloodstream or lymphatic system, and establish secondary tumours in other parts of the body. This spread is what makes cancer so dangerous and difficult to treat.
4. What are the major types of carcinogens that can cause cancer?
Carcinogens are agents that can cause cancer. As per the NCERT syllabus, they are classified into three main types:
- Physical carcinogens: These include ionising radiation like X-rays and gamma rays, and non-ionising radiation like UV rays from the sun.
- Chemical carcinogens: A major example is tobacco smoke, which contains numerous chemicals linked to lung cancer.
- Biological carcinogens: These are cancer-causing viruses, known as oncogenic viruses, which can transform normal cells into cancerous ones.
5. How is cancer detected and diagnosed in a patient?
Cancer diagnosis relies on several methods to confirm the presence and type of malignancy.
- Biopsy and Histopathology: This is the most definitive method, where a small piece of suspected tissue is examined under a microscope.
- Imaging Techniques: Radiography (X-rays), CT scans (Computed Tomography), and MRI (Magnetic Resonance Imaging) are used to visualise tumours inside the body.
- Molecular Biology: Genetic testing can identify inherited genes that increase susceptibility to certain cancers.
6. What are the common treatment approaches for cancer?
The primary methods used for cancer treatment are:
- Surgery: The physical removal of the tumour.
- Radiotherapy: Using radiation to lethally damage tumour cells while minimising harm to surrounding normal tissue.
- Chemotherapy: The use of specific cytotoxic drugs to kill cancer cells throughout the body.
- Immunotherapy: Activating the patient's own immune system to fight the cancer, often using substances called biological response modifiers like α-interferon.
7. How do proto-oncogenes and tumour suppressor genes contribute to cancer development?
Normal cells have proto-oncogenes (or cellular oncogenes) that regulate cell growth. When these genes are mutated or activated by carcinogens, they can become oncogenes that cause uncontrolled cell division, leading to cancer. Conversely, tumour suppressor genes normally function to halt cell division. If these genes are inactivated by mutation, the cell loses a critical 'brake' on its growth, which can also contribute to cancer formation.
8. Why is the loss of 'contact inhibition' a key characteristic of cancer cells?
Contact inhibition is a fundamental property of normal cells that tells them to stop dividing when they touch neighbouring cells, ensuring tissues don't become overcrowded. Cancer cells lose this property. This is a critical step in tumour formation because, without this signal, they continue to pile up on top of one another, forming the disorganized, multilayered mass that defines a tumour.
9. Explain the role of α-interferons in immunotherapy for cancer treatment.
α-interferons are biological response modifiers used in immunotherapy. Their role is not to kill cancer cells directly, but to stimulate the patient's own immune system. They help activate immune cells like natural killer (NK) cells and cytotoxic T-lymphocytes, which can then recognise and destroy tumour cells more effectively, helping the body fight the cancer.
