How does cancer develop?
Cancer is a disease in which cells grow uncontrollably and can spread to other parts of the body. It can start anywhere in the body.
Normally, when the cells grow old or become damaged, they are replaced by new cells in a systematic order. Sometimes this orderly process breaks down, and abnormal or damaged cells grow and multiply without control of our body. These cells may form tumors, which can be cancerous (malignant) or non-cancerous (benign).
Many cancers form solid tumors, but cancers of the blood (i.e. leukemia) generally do not form solid tumor.
Benign tumors do not invade nearby tissues or do not spread into distant organs. After removal of benign tumors, usually they don’t re-grow.
Malignant tumors may invade nearby tissues or may spread into distant organs, where they form new tumor (which is called metastasis). After removal, malignant tumors may re-grow at original site or along the path of surgery.
What are the risk factors of cancer?
Certain risk factors may increase the chances of developing cancer. These risk factors include following but not limited to:
- Genetic / Family history
- Tobacco use
- High alcohol consumption
- An unhealthy diet (Red and processed meat, sugary drinks and salty snacks, starchy foods, and refined carbohydrates including sugars and processed grains)
- Obesity / Lack of physical activity
- Prolonged exposure to radiation / toxic chemicals / air pollution
- Prolonged exposure to hazardous environment (i.e. pesticides, fertilisers)
- Unprotected exposure to UV light, such as sunlight
- Infection by certain viruses like H. pylori, human papillomavirus (HPV), hepatitis B, hepatitis C, HIV, and the Epstein-Barr virus.
What are the types of cancer?
Cancers are divided into types based on their origins. Four main types of cancer are:
Carcinomas
Carcinomas are the most common type of cancer. They are formed by epithelial cells, which cover the inside and outside surfaces of the body.
Carcinomas that begin in different epithelial cell types have specific names:
Adenocarcinoma is a cancer that forms in epithelial cells that produce fluids or mucus. Most cancers of the breast, lung, stomach, gall bladder, pancreas, colon, and prostate are adenocarcinomas.
Basal cell carcinoma is a cancer that begins in the lower or basal (base) layer of the epidermis, which outer layer of the skin. Most common site of basal cell carcinoma is in head & neck region, particularly near eyes.
Squamous cell carcinoma is a cancer that forms in squamous cells, which are epithelial cells that lie just beneath the outer surface of the skin. Most cancers of oral cavity (tongue, lip, buccal mucosa, upper-lower alveolus etc.), oro-pharynx, larynx, anal canal and skin are squamous cell carcinoma.
Transitional cell carcinoma is a cancer that more commonly occur in renal pelvis of kidney, ureter and urinary bladder.
Sarcomas
Sarcomas are the cancers, which occur in tissues that support and connect the body. These types of tissues include soft tissue (like muscle, fat, fibrous tissue etc.) and bones. The common sarcomas of soft tissues are leiomyosarcoma, liposarcoma, Kaposi sarcoma and most common sarcoma of bone is osteosarcoma.
Leukemias
Cancers that occur in the blood-forming tissue of the bone marrow are called leukemias. These cancers do not form solid tumors. In leukemias, there is more production of abnormal white blood cells in the blood and bone marrow. Due to low level of normal blood cells, there is inadequate transfer of oxygen from lungs to tissues, difficulty in control bleeding and low immunity.
There are four common types of leukemia: Acute lymphocytic leukemia,Chronic lymphocytic leukemia,Acutemyeloid leukemia, andChronic myeloid leukemia.
Lymphomas
Lymphoma is cancer of lymphocytes (T cells or B cells) (part of white blood cells), which fight against disease and they are part of the immune system. In lymphoma, abnormal lymphocytes build up in lymph nodes, lymph vessels, as well as in other organs ofthe body.
There are two main types of lymphoma: Hodgkin lymphoma and Non-Hodgkin lymphoma
Multiple Myeloma
Multiple myeloma is cancer of plasma cells, which is another type of immune cell. The abnormal plasma cells, called myeloma cells, build up in the bone marrow and form tumors in bones all through the body.
Melanoma
Melanoma is a cancer of melanocytes, which make melanin (the pigment that gives skin its colour). Most melanomas occur on the skin, but melanomas can also occur in other pigmented tissues, such as the eye.
Brain and Spinal Cord Tumors
There are different types of brain and spinal cord tumors. These tumors are named based on the type of cell from which they are formed, like astrocytoma, glioblastoma, ependymoma, schwannoma, meningioma etc.
Germ Cell Tumors
Germ cell tumors are a type of tumor that begins in the cells that give rise to sperm or eggs. These tumors can occur almost anywhere in the body and can be either benign or malignant.
Neuroendocrine Tumors
Neuroendocrine tumors are seen in cells that release hormones into the blood in response to a signal from the nervous system. These tumors, which may make higher amounts of hormones, can cause many different symptoms. Neuroendocrine tumors may be benign or malignant.
Symptoms
Signs and symptoms of cancer depend upon site of origin in the body.Some general signs and symptoms associated with, but not specific to, cancer include:
- Swelling / lump or area of thickening under the skin
- Weight loss
- Changes in size or colour of mole
- Changes in bowel or bladder habits
- Persistent cough
- Difficulty in breathing
- Difficulty in swallowing
- Hoarseness of voice
- Indigestion or discomfort after eating
- Blood in vomiting / stool
- Persistent unexplained fever
- Headache / Giddiness / Diminution of vision
How does cancer spread?
As a cancer grows, the blood stream (hematogenous spread) or lymph vessels (lymphatic spread) may carry cancer cells to other parts of the body. The cancer cells grow and may develop tumors at new site, which is known as metastasis. To know more how cancer spreads kindly click here.
Lymph nodes are the first places, where a cancer often spreads, which is known lymphatic spread.
The common site for hematogenous (via blood stream) spread are lungs, liver, bone, brain and adrenals.
How cancer is diagnosed?
Cancer is diagnosed after having proper consultation and clinical examination by a doctor according to the symptoms. A doctor advises for various tests according to the history and symptom of the patient. The tests include various clinical (endoscopy), pathological (blood reports, tumor markers, biopsy etc.) and radiological (X-ray, mammography, sonography, CT scan MRI or PET-CT etc.) investigations, depending upon signs and symptoms of the patient. The radiological investigations show site of disease in the body, but biopsy is the final answer to confirm / to rule out cancer and to determine the type (adenocarcinoma / squamous cell carcinoma / sarcoma) of cancer, if present. To know more about PET-CT, kindly click here. To know more about tumour markers, kindly click here.
Cancer Statistics in India (according to ICMR)
- One woman dies of cervical cancer every 8 minutes in India.
- For every 2 women newly diagnosed with breast cancer, one woman dies of it in India.
- Tobacco (smoked and smokeless) use accounted for 3,17,928 deaths (approx) in men and women in 2018.
- Estimated number of people with cancer: around 2.7 million (2020)
- Every year, new cancer patients registered: 13.9 lakhs
- Cancer-related deaths per year: 8.5 lakhs
- Risk of developing cancer before the age of 75 years for Indians: Overall (both sexes included): 1 in 9; Male: 1 in 68; Female: 1 in 29
Cancers of oral cavity, stomach and lungs account for over 25% of cancer deaths in males and cancer of uterine cervix, breast and oral cavity account for 25% cancers in females.
The top five cancers in men and women account for 47.2% of all cancers; these cancers can be prevented, screened for and/or detected early and treated at an early stage. This could significantly reduce the death rate from these cancers.
Five most common cancers in male and females in India are following:
| Male | Female | |
| 1 | Oral cavity (lip, tongue) | Breast |
| 2 | Lung | Uterine cervix |
| 3 | Stomach | Ovary |
| 4 | Colo-rectal | Oral cavity (lip, tongue) |
| 5 | Esophagus | Colo-rectal |
National Cancer Awareness Day in India
India observes National Cancer Awareness Day on 7 November every year since 2014 to raise awareness about early detection of cancer. National Cancer Awareness Day was first announced by Union Health Minister, Dr. Harsh Vardhan in September 2014.
National Cancer Awareness Day coincides with the birth anniversary of the Nobel-prize winner scientist Madame Curie. Marie Curie (Born in 1867, in Warsaw, Poland) is remembered for her discovery of radium and polonium, and her contribution to fight against cancer. Her work led to the development of nuclear energy and radiotherapy for the treatment of cancer.