What is cancer?
Cancer is an abnormal growth of cells. Cancer cells quickly reproduce event without
enough space and nutrients. They also grow despite signals sent from the body to stop
reproduction. Cancer cells are often shaped differently from healthy cells. They do
not work well and can spread to many parts of the body. Tumors, masses, or lesions
are names for abnormal growths of tissue that can become cancer. Their growth is not
Oncology is the branch of medicine that studies the diagnosis and treatment of cancer.
What do the terms benign and malignant mean?
Tumors can be benign (noncancerous) or malignant (cancerous). Benign tumors tend to
grow slowly and do not spread. Malignant tumors can grow quickly. They invade and
destroy nearby normal tissues and spread throughout the body.
What do the terms locally invasive and metastatic mean?
Cancer is malignant because it can be locally invasive and metastatic:
Locally invasive. The tumor can invade the tissues surrounding it by sending out "fingers" of
cancerous cells into the normal tissue.
Metastatic. The tumor can send cells into other tissues in the body. These may be far from
the original tumor.
What are primary tumors?
The original tumor is called the primary tumor. Its cells, which can break off and travel through the body, can start to form new
tumors in other organs. These new tumors are called secondary tumors. The cancerous cells travel through your blood – the circulatory system – or lymphatic
system to form secondary tumors. The lymphatic system is a series of small vessels
that collect waste from cells. It carries it into larger vessels, and finally into
lymph nodes. Lymph fluid eventually drains into your bloodstream.
How is each cancer type named?
Cancer is named after the part of the body where it first started. When cancer spreads,
it keeps this same name. For instance, if kidney cancer spreads to your lungs, it’s
still kidney cancer, not lung cancer. (The cancer in the lung would be an example
of a secondary tumor.)
Staging is the process of figuring out if cancer has spread and, if so, how far. More
than one system is used for staging cancer. The definition of each stage depends on
the type of cancer.
What are the different types of cancer?
Cancer is not just one disease. Rather, it’s a group of diseases, all of which cause
cells in the body to change and grow out of control. Cancers are classified by the
kind of fluid or tissue from which they come from. Or they can be classified due to
the location in the body where they first started. Some cancers are of mixed types.
These categories are the tissue and blood classifications of cancer:
Carcinoma. A carcinoma is a cancer found in body tissue called epithelial tissue. It
covers or lines surfaces of organs, glands, or body structures. For instance,
a cancer of the lining of the stomach is called a carcinoma. The two most common types
of carcinomas are include squamous and adenocarcinomas. Many carcinomas affect
organs or glands that are involved with secretion. These include breasts that
make milk. Carcinomas account for 80% to 90% of all cancers.
Sarcoma. A sarcoma is a malignant tumor growing from connective tissues. These can
include cartilage, fat, muscle, tendons, and bones. The most common sarcoma,
a tumor on the bone, usually occurs in young adults. Examples include osteosarcoma
(bone) and chondrosarcoma (cartilage).
Lymphoma. Lymphoma is a cancer that starts in the nodes or glands of the lymphatic system.
The lymphatic system makes white blood cells and cleans body fluids. Some lymphomas
start in lymph tissue in organs. These include the brain or stomach. Lymphomas
are classified into two categories: Hodgkin lymphoma and non-Hodgkin lymphoma.
Leukemia. Leukemia is also known as blood cancer. It’s a cancer of the bone marrow that
keeps the marrow from making normal red and white blood cells and platelets.
White blood cells are needed to fight infections. Red blood cells are needed
to prevent anemia. Platelets keep the body from bruising and bleeding easily.
Examples include acute myelogenous leukemia, chronic myelogenous leukemia, acute
lymphocytic leukemia, and chronic lymphocytic leukemia. The terms myelogenous
and lymphocytic indicate the type of cells that are involved.
Myeloma. Myeloma grows in the plasma cells of bone marrow. In some cases, the myeloma
cells collect in one bone and form a single tumor. This is called a plasmacytoma.
However, in other cases, the myeloma cells collect in many bones, forming many
tumors. This is called multiple myeloma.
What causes cancer?
Cancer has no single cause. Experts think that it’s the interaction of many factors
that leads to cancer. The factors may be genetic, environmental, or lifestyle characteristics.
What are the risk factors for cancer?
Some cancers have been linked with certain risk factors. A risk factor is anything
that may increase your chance of getting a disease. A risk factor does not necessarily
cause the disease, but it may mean you’re more likely to get it.
People with an increased risk of cancer can reduce their risk by keeping up with screenings.
Reducing certain risk factors can also help. Cancer treatment tends to work better
when the cancer is found early. Risk factors of cancer include:
Lifestyle factors. These include smoking, a high-fat diet, and exposure to ultraviolet light (UV
radiation from the sun). These are only risk factors for adult cancers. Most children
with cancer are too young to have been exposed to lifestyle factors long-term.
Genetic factors. Family history, inheritance, and genetics may play a role in some cancers. Some
cancers run in families. Some gene alterations are inherited. However, this does
not mean that the person will get cancer. It just means that the chance of getting
cancer is higher. It isn’t known if the disease is caused by a genetic mutation,
other factors, or a coincidence.
Virus exposure. Exposures to certain viruses have been linked to cancer. These include the human
papillomavirus (HPV) and HIV, the virus that causes AIDS. These viruses may change
your cells in some way. Over time, these changes may become a cancer cell that
makes more cancer cells. Cancer isn’t contagious. You cannot get it from another
Environmental factors. People with certain jobs, such as painters, farmers, construction workers, and
those in the chemical industry, seem to have a higher risk of some cancers. This
is likely due to exposures to certain chemicals. Other environmental factors
in your home may also be linked to cancer. These can include radon, a radioactive
How do genes affect cancer growth?
Certain genes contribute to cancer. Almost all cancers have some type of genetic alteration.
A small percentage of these alterations are inherited. But the rest happen by chance.
Three main types of genes can affect cell growth. They are altered, or mutated, in
certain types of cancers. These include:
Oncogenes. These genes control the normal growth of cells. Scientists say oncogenes are
like a cancer "switch" that most people have in their bodies. It isn’t known
what "flips the switch" to make abnormal cancer cells grow, though.
Tumor suppressor genes. These genes are able to spot abnormal growth and reproduction of damaged cells,
or cancer cells. They can interrupt their reproduction. But if the tumor suppressor
genes are mutated and don’t work well, cancer may grow.
Mismatch-repair genes. These genes help find errors when DNA is copied to make a new cell. If the DNA
does not "match" perfectly, these genes repair the mismatch and correct the error.
If these genes aren’t working well, however, errors in DNA can travel to new
cells. This causes them to be damaged.
In most cases, the number of cells in our body tissues is tightly controlled. New
cells are made for normal growth and development. They also replace dying cells. Cancer
is a loss of this balance. It occurs due to genetic changes that "tip the balance"
in favor of excessive cell growth.
How do childhood and adult cancers differ?
Diagnosis, treatment, and prognosis for childhood cancers are different than for adult
cancers. The main differences are the survival rate and the cause of the cancer. The
five-year survival rate for childhood cancer is about 83%. The five-year survival
rate for adult cancers is about 68%. This may be because childhood cancer responds
better to treatment. Plus, a child can tolerate more aggressive treatment.
Childhood cancers often occur in the stem cells. These are simple cells that make
other types of specialized cells that the body needs. A cell change that occurs by
chance is often what causes childhood cancer. In adults, the type of cell that becomes
cancerous is usually an epithelial cell. This is one of the cells that line the body
cavity and cover the body surface. These include the surfaces of organs, glands, or
body structures. Cancer in adults usually occurs from environmental exposures to these
cells over time. Adult cancers are sometimes called as acquired for this reason.