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- An Introduction to Cancer: A Primer for High School Students
What is Cancer?
The Masterman School
Last Modified: November 1, 2001
Cancer is a general term for more than 100 diseases characterized
by the uncontrolled , abnormal growth of cells in different parts
of the body. Certain types of cancer can often spread to from
one location to another. Cancer cells grow geometrically, meaning
first there is one cancer cell, then two, then four, then eight
and so on. Cancerous tumors are grouped into one of two categories,
malignant or benign. Evidence of the existence of cancer can be
dated back as far as prehistoric times. It has been found in the
skeletons of prehistoric animals and even in Egyptian mummies.
Cancer is classified into five major groups:
Carcinoma is a cancerous tumor originating in the epithelial system
(surface tissue of body organs). Sometimes people develop carcinoma
of unknown primary. This is when malignant cells are found somewhere
in the body, but their origin, or the place where they first started
growing, is unknown. Carcinoma is the most common form of cancer
accounting for nearly 80% to 90% of all cases.
Sarcoma is a disease in which malignant tumors are found in the
bone, cartilage, muscle, fibrous connective tissue, or fatty tissue.
There are three main types of sarcomas including soft tissue,
Kaposi's, and Ewing's. Soft tissue sarcomas develop in the muscles,
fat, blood vessels, nerves, and synovial tissues (tissues around
joints). Kaposi's sarcoma is found in the tissues under the skin
or mucous membranes which line the mouth, nose, and anus. It causes
red or purple lesions on the skin and spreads to other parts of
the body. Ewing's sarcoma is a rare disease in which cancerous
cells are found in the bone. It occurs most commonly in the pelvis,
the thigh bone, the upper arm bone, or the ribs. Ewing's sarcoma
is most often seen in teenagers.
Myeloma is the uncontrolled growth of plasma cells in the bone
marrow. Plasma cells are a critical part of the body's immune
system. They are manufactured in bone marrow and then move into
the bloodstream. In most cases plasma cell tumors are monoclonal
(originating from a single defective cell that began the cycle
of uncontrolled cancerous growth).
Lymphoma is a cancerous tumor originating in the lymph system.
The lymph system is a connecting network of glands and vessels
which produce and circulate lymph through the body. Lymph is a
colorless, watery fluid that contains white blood cells called
lymphocytes. Along the vessels are organs called nodes. Lymph
nodes are found in the neck, under the arms, in the groin and
abdomen. Lymph nodes make and store infection fighting cells.
When lymphoma occurs, cells in the lymphatic system grow abnormally.
They divide to rapidly and grow without order or control. The
cells are immature and do not die like a normal cell. They continue
to divide as immature cells that cannot do their jobs well. Too
much tissue is formed and tumors begin to grow. Because there
is lymph tissue in many parts of the body, the cancer cells may
spread to other parts of the body such as the liver or spleen
or into the bone marrow. Lymphomas are divided into Hodgkin's
and non-Hodgkin's lymphomas. They are distinguished by cell type
and they share similar symptoms such as painless swelling of the
lymph nodes, fever, and fatigue.
Leukemia is a malignant disorder of the body's blood forming tissue
- mainly bone marrow, lymph nodes and spleen. In leukemia, the
blood forming tissues flood the bloodstream and lymph system with
immature white blood cells. The immature cells cannot fight infections.
They reduce the production of normal red blood cells and tiny
discs called platelets. Uncontrolled leukemia causes infections
due to the lack of normal infection fighting white blood cells;
severe anemia due to the lack of oxygen carrying red blood cells;
and bruising and hemorrhaging, due to the lack of platelets. Leukemia
is divided into two categories, acute and chronic. Acute affects
immature white blood cells, progresses rapidly, and is most is
often seen in children. Chronic leukemia occurs most frequently
in adults and progresses slowly.
The study of cancerous tumors is called oncology. Doctors who
specialize in the diagnosis and treatment of cancer are called