Cancer Overview

Cancer Overview

What is cancer?

Cancer is an abnormal growth of cells. The whole body is made of cells that act and
grow in controlled ways as the body needs them. The cells are controlled by genes. The
genes in any 1 of these cells can become damaged. Then the cell can grow out of control
and become cancer.

Cancer cells quickly grow and
divide. This happens even when there’s not enough space and nutrients. They also grow
despite signals sent from the body telling them to stop.

Cancer cells don’t look the same as
healthy cells. They don’t work the way they should. They can spread to other parts of
the body. Tumors, masses, or lesions are names for abnormal growths of cells that can
become cancer.

Oncology is the branch of medicine that studies and treats cancer.

What do
benign and malignant mean?

Tumors can be benign or malignant.

Benign tumors are not cancer. They tend to grow
slowly. They do not spread to other parts of the body.

Malignant tumors are cancer. They can grow quickly.
They grow into and destroy nearby normal tissues. And they can spread throughout the
body.

What do
locally invasive and metastatic mean?

Cancer can be locally invasive and metastatic.

Locally invasive cancer has spread to nearby tissues.
It can cause problems by pressing on nearby tissues and organs. This can make them
unable to work the way they should.

Metastatic cancer has spread from where it first
started.
It is growing in and affecting another part of the body. Cancer cells
spread by getting into your blood stream or lymph system. The lymph system is a series
of small vessels that carry a fluid called lymph. Lymph collects waste from cells. It
carries it into lymph nodes where the waste is filtered out. Lymph then drains into your
bloodstream.

Cancer cells can travel through 1 of these pathways to any part of
the body. Then they grow and form a tumor there.

What are
primary tumors?

The original tumor is called the primary tumor.
This is the place where the cancer first started. These cells can break off and
travel through the body. Then they can start to form new tumors in other organs.

These new tumors are called secondary tumors.
The cancer cells travel through your blood or lymph system to form these tumors.

How is each cancer type named?

Cancer is named after the part of the body where it first started. This is the place
the original tumor formed.

When cancer spreads, it keeps this
same name. For example, if kidney cancer spreads to your lungs, it’s still called kidney
cancer. The cancer in the lung is a secondary tumor. The cancer cells in the lung look
like the cancer cells in the kidney. They don’t look like lung cancer cells. This may be
called kidney cancer with lung metastasis or metastatic kidney cancer to the lung. It’s
not called lung cancer.

What are the different types of cancer?

Cancer is not just 1 disease. It’s a group of many diseases, all of which cause cells
in the body to change and grow out of control. Cancers are defined by the kind of cell
they start in. Or they can be defined by the place in the body where they first started.
Some cancers are of mixed types. These are the most common categories of cancer:

  • Carcinoma. This is cancer found in cells that make up epithelial tissue.
    This tissue covers or lines the surfaces of organs, glands, and body structures.
    Carcinoma usually forms a solid tumor. Carcinomas are 80% to 90% of all
    cancers.

  • Sarcoma. This is cancer that starts in connective tissue cells. These can
    include blood and lymph vessel, cartilage, fat, muscle, tendon, and bone cells.
    For example, osteosarcoma is the most common type of cancer that starts in the
    bone. Chondrosarcoma is cancer that starts in cartilage cells.

  • Lymphoma. This is cancer that starts in a type of white blood cell called
    a lymphocyte. These cells are part of the immune system, Lymphoma cells can build
    up in lymph nodes and other lymph tissues. Lymphomas are grouped into 2
    categories: Hodgkin lymphoma and non-Hodgkin lymphoma.

  • Leukemia. This is called a blood cancer. It starts in the cells in the
    bone marrow that make blood cells. This type of cancer 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 carry oxygen and carbon
    dioxide through the body. Platelets keep the body from bruising and bleeding
    easily. There are 4 main types of leukemia. They are acute myelogenous leukemia
    (AML), chronic myelogenous leukemia (CML), acute lymphocytic leukemia (ALL), and
    chronic lymphocytic leukemia (CLL). The terms myelogenous and lymphocytic mean the
    type of cells that are involved. Acute and chronic tell how fast the cells are
    growing.

  • Myeloma. This type of cancer starts in the plasma cells of bone marrow. In
    some cases, the myeloma cells collect in 1 bone and form a single tumor. This is
    called a plasmacytoma. In other cases, the myeloma cells collect in many bones. It
    forms 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. These
factors cause a change in the genes of a cell so that it divides and grows in an
uncontrolled way.

Who is at
risk for cancer?

Some
cancers have been linked with risk factors. A risk factor is anything that may increase
your chance of getting a disease. A risk factor doesn’t necessarily cause the disease.
But it may mean you’re more likely to get it.

People with an increased risk of some cancers can help reduce their risk by getting
regular screening tests. This allows pre-cancer cells to be found and treated before
they turn into cancer cells. Some colon, rectal, and cervical cancers can be prevented
with screening.

Reducing certain risk factors can
also help. Cancer treatment tends to work better when the cancer is found early. This
means when it’s small and hasn’t spread. Some known risk factors for cancer in adults
include:

  • Lifestyle factors. These include smoking, a high-fat diet, and exposure to
    ultraviolet light (UV) from the sun or UV lamps. These are only risk factors for
    adult cancers. Most children with cancer are too young to have been exposed to
    lifestyle factors long enough to have them cause cancer.

  • Genetic factors. Family health history and genes play a role in some
    cancers. Some cancers run in families. Some gene changes are inherited. This means
    people in these families have a higher risk for some types of cancers. But not
    every family will get cancer. In many cases, it isn’t known if the disease is
    caused by a gene change, other factors, or a coincidence.

  • Virus exposure. Contact with certain viruses have been linked to cancer.
    These include the human papillomavirus (HPV) and HIV, the virus that causes AIDS.
    These viruses can cause cells changes that may lead to cancer over time. But
    cancer isn’t contagious. You can’t get it from contact with another person.

  • Environmental factors. People with certain jobs seem to have a higher risk
    of some cancers. This includes painters, farmers, construction workers, and people
    in the chemical industry. This is likely due to contact with certain chemicals.
    Some environmental factors in your home may be linked to cancer. These can
    include a natural radioactive gas called radon, and arsenic in well water.

How do genes affect cancer growth?

Certain genes contribute to cancer. All cancers have some type of genetic change
(mutation). A small amount of these mutations are inherited. But the rest happen by
chance.

There
are 3 main types of genes that can affect cell growth. They are changed (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 take away control and allow abnormal cancer
    cells grow. 

  • Tumor suppressor genes. These genes are able to spot abnormal growth and
    reproduction of damaged cells, like cancer cells. They can stop them from
    reproducing. But if the tumor suppressor genes are mutated and don’t work well,
    cancer cells can grow.

  • Mismatch-repair genes. These genes help find errors when the DNA in genes
    is copied to make a new cell. If the DNA does not “match” perfectly, these genes
    repair the mismatch and correct the error. But if these genes aren’t working well,
    errors in DNA can transferred to the 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’re also made to replace damaged or dead
cells. Cancer is a loss of this balance. It starts when genetic changes “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 5-year survival rate for
childhood cancer is about 83%. This means that 83 out of 100 children with cancer will
survive 5 years. The 5-year survival rate for adult cancers is about 67%. This may be
because childhood cancer responds better to certain treatments. Unlike adults, children
don’t usually have other health problems that can affect cancer treatment.

A
cell change that occurs by chance is the most common cause of most childhood cancers. In
adults, lifestyle and environmental risk factors are strongly linked to cancer. Adult
cancers are sometimes called acquired for this reason.

Another key difference is clinical trials. Most children are treated
at special childhood cancer centers and most are treated in clinical trials. This means
they’re treated by experts. They get the very best available, cutting-edge treatments
that help improve childhood cancer treatment at a rapid rate. Fewer than 1 in 20 adults
takes part in cancer clinical trials. This affects the development of new procedures and
treatments.