What is Cancer? What Causes Cancer?
Cancer is a class of diseases characterized by out-of-control cell growth. There are over 100 different
types of cancer, and each is classified by the type of cell that is initially affected.
Cancer harms the body when damaged cells divide uncontrollably to form lumps or masses of tissue
called tumors (except in the case of leukemia where cancer prohibits normal blood function by abnormal
cell division in the blood stream). Tumors can grow and interfere with the digestive, nervous, and
circulatory systems, and they can release hormones that alter body function. Tumors that stay in one spot
and demonstrate limited growth are generally considered to be benign.
More dangerous, or malignant, tumors form when two things occur:
1. a cancerous cell manages to move throughout the body using the blood
or lymph systems, destroying healthy tissue in a process called invasion
2. that cell manages to divide and grow, making new blood vessels to feed
itself in a process called angiogenesis.
When a tumor successfully spreads to other parts of the body and grows, invading and destroying other
healthy tissues, it is said to have metastasized. This process itself is called metastasis, and the result is a
serious condition that is very difficult to treat.
In 2007, cancer claimed the lives of about 7.6 million people in the world. Physicians and researchers
who specialize in the study, diagnosis, treatment, and prevention of cancer are called oncologists.
What causes cancer?
Cancer is ultimately the result of cells that uncontrollably grow and do not die. Normal cells in the body
follow an orderly path of growth, division, and death. Programmed cell death is called apoptosis, and
when this process breaks down, cancer begins to form. Unlike regular cells, cancer cells do not
experience programmatic death and instead continue to grow and divide. This leads to a mass of
abnormal cells that grows out of control.
What are the symptoms of cancer?
Cancer symptoms are quite varied and depend on where the cancer is located, where it has spread, and
how big the tumor is. Some cancers can be felt or seen through the skin - a lump on the breast or testicle
can be an indicator of cancer in those locations. Skin cancer (melanoma) is often noted by a change in a
wart or mole on the skin. Some oral cancers present white patches inside the mouth or white spots on the
Other cancers have symptoms that are less physically apparent. Some brain tumors tend to present
symptoms early in the disease as they affect important cognitive functions. Pancreas cancers are usually
too small to cause symptoms until they cause pain by pushing against nearby nerves or interfere with
liver function to cause a yellowing of the skin and eyes called jaundice. Symptoms also can be created as
a tumor grows and pushes against organs and blood vessels. For example, colon cancers lead to
symptoms such as constipation, diarrhea, and changes in stool size. Bladder or prostate cancers cause
changes in bladder function such as more frequent or infrequent urination.
As cancer cells use the body's energy and interfere with normal hormone function, it is possible to present
symptoms such as fever, fatigue, excessive sweating, anemia, and unexplained weight loss. However,
these symptoms are common in several other maladies as well. For example, coughing and hoarseness
can point to lung or throat cancer as well as several other conditions.
When cancer spreads, or metastasizes, additional symptoms can present themselves in the newly
affected area. Swollen or enlarged lymph nodes are common and likely to be present early. If cancer
spreads to the brain, patients may experience vertigo, headaches, or seizures. Spreading to the lungs
may cause coughing and shortness of breath. In addition, the liver may become enlarged and cause
jaundice and bones can become painful, brittle, and break easily. Symptoms of metastasis ultimately
depend on the location to which the cancer has spread.
What Is Leukemia? What Causes Leukemia?
The word Leukemia comes from the Greek leukos which means "white" and aima which means "blood". It
is cancer of the blood or bone marrow (which produces blood cells). A person who has leukemia suffers
from an abnormal production of blood cells, generally leukocytes (white blood cells).
The DNA of immature blood cells, mainly white cells, becomes damaged in some way. This abnormality
causes the blood cells to grow and divide chaotically. Normal blood cells die after a while and are
replaced by new cells which are produced in the bone marrow. The abnormal blood cells do not die so
easily, and accumulate, occupying more and more space. As more and more space is occupied by these
faulty blood cells there is less and less space for the normal cells - and the sufferer becomes ill. Quite
simply, the bad cells crowd out the good cells in the blood.
In order to better understand what goes on we need to have a look at what the bone marrow does.
Function of the bone marrow
The bone marrow is found in the inside of bones. The marrow in the large bones of adults produces blood
cells. Approximately 4% of our total bodyweight consists of bone marrow.
There are two types of bone marrow: 1. Red marrow, made up mainly of myeloid tissue. 2. Yellow
marrow, made up mostly of fat cells. Red marrow can be found in the flat bones, such as the breast bone,
skull, vertebrae, shoulder blades, hip bone and ribs. Red marrow can also be found at the ends of long
bones, such as the humerus and femur.
White blood cells (lymphocytes), red blood cells and platelets are produced in the red marrow. Red blood
cells carry oxygen, white blood cells fight diseases. Platelets are essential for blood clotting. Yellow
marrow can be found in the inside of the middle section of long bones.
If a person loses a lot of blood the body can convert yellow marrow to red marrow in order to raise blood
White blood cells, red blood cells and platelets exist in plasma - Blood plasma is the liquid component of
blood, in which the blood cells are suspended.
Types of leukemia
Chronic and Acute
Experts divide leukemia into four large groups, each of which can be Acute, which is a rapidly progressing
disease that results in the accumulation of immature, useless cells in the marrow and blood, or Chronic,
which progresses more slowly and allows more mature, useful cells to be made. In other words, acute
leukemia crowds out the good cells more quickly than chronic leukemia.
Lymphocytic and Myelogenous
Leukemias are also subdivided into the type of affected blood cell. If the cancerous transformation occurs
in the type of marrow that makes lymphocytes, the disease is called lymphocytic leukemia. A lymphocyte
is a kind of white blood cell inside your vertebrae immune system. If the cancerous change occurs in the
type of marrow cells that go on to produce red blood cells, other types of white cells, and platelets, the
disease is called myelogenous leukemia.
To recap, there are two groups of two groups - four main types of leukemia, as you can see in the
Acute Lymphocytic Leukemia (ALL), also known as Acute Lymphoblastic Leukemia - This is the most
common type of leukemia among young children, although adults can get it as well, especially those over
the age of 65. Survival rates of at least five years range from 85% among children and 50% among
adults. The following are all subtypes of this leukemia: precursor B acute lymphoblastic leukemia,
precursor T acute lymphoblastic leukemia, Burkitt's leukemia, and acute biphenotypic leukemia.
Chronic Lymphocytic Leukemia (CLL) - This is most common among adults over 55, although younger
adults can get it as well. CLL hardly ever affects children. The majority of patients with CLL are men, over
60%. 75% of treated CLL patients survive for over five years. Experts say CLL is incurable. A more
aggressive form of CLL is B-cell prolymphocytic leukemia.
Acute Myelogenous Leukemia (AML) - AML is more common among adults than children, and affects
males significantly more often than females. Patients are treated with chemotherapy. 40% of treated
patients survive for over 5 years. The following are subtypes of AMS - acute promyelocytic leukemia,
acute myeloblastic leukemia, and acute megakaryoblastic leukemia.
Chronic Myelogenous Leukemia (CML) - The vast majority of patients are adults. 90% of treated
patients survive for over 5 years. Gleevec (imatinib) is commonly used to treat CML, as well as some
other drugs. Chronic monocytic leukemia is a subtype of CML.
Symptoms of leukemia
Blood clotting is poor - As immature white blood cells crowd out blood platelets, which are crucial for
blood clotting, the patient may bruise or bleed easily and heal slowly - he may also develop petechiae
(a small red to purple spot on the body, caused by a minor hemorrhage).
Affected immune system - The patient's white blood cells, which are crucial for fighting off infection,
may be suppressed or not working properly. The patient may experience frequent infections, or his
immune system may attack other good body cells.
Anemia - As the shortage of good red blood cells grows the patient may suffer from anemia - this may
lead to difficult or labored respiration (dyspnea) and pallor (skin has a pale color caused by illness).
Other symptoms - Patients may also experience nausea, fever, chills, night sweats, flu-like symptoms,
and tiredness. If the liver or spleen becomes enlarged the patient may feel full and will eat less,
resulting in weight loss. Headache is more common among patients whose cancerous cells have
invaded the CNS (central nervous system).
Precaution - As all these symptoms could be due to other illnesses. A diagnosis of leukemia can only
be confirmed after medical tests are carried out.
What causes leukemia?
Experts say that different leukemias have different causes. The following are either known causes, or
strongly suspected causes:
Artificial ionizing radiation
Viruses - HTLV-1 (human T-lymphotropic virus) and HIV (human immunodeficiency virus)
Benzene and some petrochemicals
Alkylating chemotherapy agents used in previous cancers
Maternal fetal transmission (rare)
Genetic predisposition - some studies researching family history and looking at twins have indicated
that some people have a higher risk of developing leukemia because of a single gene or multiple
Down syndrome - people with Down syndrome have a significantly higher risk of developing leukemia,
compared to people who do not have Down syndrome. Experts say that because of this, people with
certain chromosomal abnormalities may have a higher risk.
Electromagnetic energy - studies indicate there is not enough evidence to show that ELF magnetic (not
electric) fields that exist currently might cause leukemia. The IARC (International Agency for Research
on Cancer) says that studies which indicate there is a risk tend to be biased and unreliable.
Treatments for leukemia
As the various types of leukemias affect patients differently, their treatments depend on what type of
leukemia they have. The type of treatment will also depend on the patient's age and his state of health.
In order to get the most effective treatment the patient should get treatment at a center where doctors
have experience and are well trained in treating leukemia patients. As treatment has improved, the aim of
virtually all health care professionals should be complete remission - that the cancer goes away
completely for a minimum of five years after treatment.
Treatment for patients with acute leukemias should start as soon as possible - this usually involves
induction therapy with chemotherapy, and takes place in a hospital.
When a patient is in remission he will still need consolidation therapy or post induction therapy. This may
involve chemotherapy, as well as a bone marrow transplant (allogeneic stem cell transplantation).
If a patient has Chronic Myelogenous Leukemia (CML) his treatment should start as soon as the
diagnosis is confirmed. He will be given a drug, probably Gleevec (imatinib mesylate), which blocks the
BCR-ABL cancer gene. Gleevec stops the CML from getting worse, but does not cure it. There are other
drugs, such as Sprycel (dasatinib) and Tarigna (nilotinb), which also block the BCR-ABL cancer gene.
Patients who have not had success with Gleevec are usually given Sprycel and Tarigna. All three drugs
are taken orally. A bone marrow transplant is the only current way of curing a patient with CML. The
younger the patient is the more likely the transplant will be successful.
Patients with Chronic Lymphocytic Leukemia (CLL) may not receive any treatment for a long time after
diagnosis. Those who do will normally be given chemotherapy or monoclonal antibody therapy. Some
patients with CLL may benefit from allogeneic stem cell transplantation (bone marrow transplant).
All leukemia patients, regardless of what type they have or had, will need to be checked regularly by their
doctors after the cancer has gone (in remission). They will undergo exams and blood tests. The doctors
will occasionally test their bone marrow. As time passes and the patient continues to remain free of
leukemia the doctor may decide to lengthen the intervals between tests.
What is AIDS?
AIDS stands for: Acquired Immune Deficiency Syndrome
AIDS is a medical condition. A person is diagnosed with AIDS when their immune system is too weak to
fight off infections.
Since AIDS was first identified in the early 1980s, an unprecedented number of people have been affected
by the global AIDS epidemic. Today, there are an estimated 33.3 million people living with HIV and
What causes AIDS?
AIDS is caused by HIV.
HIV is a virus that gradually attacks immune system cells. As HIV progressively damages these cells, the
body becomes more vulnerable to infections, which it will have difficulty in fighting off. It is at the point
of very advanced HIV infection that a person is said to have AIDS. It can be years before HIV has
damaged the immune system enough for AIDS to develop.
What are the symptoms of AIDS?
A person is diagnosed with AIDS when they have developed an AIDS related condition or symptom,
called an opportunistic infection, or an AIDS related cancer. The infections are called ‘opportunistic’
because they take advantage of the opportunity offered by a weakened immune system.
It is possible for someone to be diagnosed with AIDS even if they have not developed an opportunistic
infection. AIDS can be diagnosed when the number of immune system cells (CD4 cells) in the blood of
an HIV positive person drops below a certain level.
Is there a cure for AIDS?
Worryingly, many people think there is a 'cure' for AIDS - which makes them feel safer, and perhaps take
risks that they otherwise wouldn't. However, there is still no cure for AIDS. The only way to stay safe is
to be aware of how HIV is transmitted and how to prevent HIV infection.