Cancer, Neoplasia, Tumor, Neoplasm
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The word cancer comes from the Latin
(originally Greek) derived term for crab, because of
the way a cancer adheres to any part that it seizes
upon in an obstinate manner like the crab. Hippocrates
first described cancer as having a central body with
the tendency to reach out and spread like "the
arms of a crab." Besides the popular, generic term
"cancer" used by most people, there is
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another more technical term: neoplasia. Neoplasia (neo = new,
plasia = tissue or cells) or neoplasm literally means new tissue
in Greek. This indicates that cancers are actually new growths
of cells in the body.
Another term for cancer is "malignant tumor." Tumor literally
means "swelling" or "mass." In this case, it refers to
a mass of non-structured new cells, which have no known purpose
in the physiological function of the body.
There are two general types of tumors: benign (non-cancerous)
tumors and malignant (cancerous) tumors. A benign tumor is
composed of cells that will not invade other unrelated tissues
or organs of the body, although it may continue to grow in
size abnormally. A malignant tumor is composed of cells that
invade the basement
membrane and invade or spread to other parts of the body.
This occurs either by direct extension to neighboring organs
and/or tissues or by metastasizing to distant sites by means
of the vascular system (the blood stream), the lymphatic system,
or by seeding or implantation of cancer cells in body cavities.
Terms such as "mass" and "lump" are used to describe any
overgrowth of tissue. However, these terms may not necessarily
mean that such growths contain cancer cells.
Types of Abnormal Cell Growth
In addition to neoplasia, there are several other terms referring
to abnormal cell growth. These include the following:
Hyperplasia refers
to an abnormal increase in the number of cells, which are
in a normal component of that tissue and are arranged in a
normal fashion with subsequent enlargement of the affected
part. One example is thyroid hyperplasia, an enlargement of
the thyroid gland caused by an abnormal rapid growth of the
epithelial cells lining the follicles. Another example is:
Guitar strumming leads to hyperplasia of the cells on the
thumb (a callus is formed). The callus on the thumb is a hyperplastic
growth.
Hypertrophy refers
to an abnormal increase in the size of each cell, for example,
the increase in cell size of cardiac muscle.
Metaplasia refers to
the replacement of one mature cell type with another mature
cell type, for example, squamous metaplasia of the respiratory
columnar epithelium - as evidenced by the metaplastic cough
of a smoker.
Dysplasia refers to
the replacement of one mature cell type with a less mature
cell type, for example, dysplasia of the cervix epithelium.
Hyperplasia, metaplasia, and dysplasia are reversible because
they are results of a stimulus. Neoplasia is irreversible
because it is autonomous.
Tumor Terminology Generalizations
Names of benign tumors usually end with "oma" as suffixes
regardless of their cell type. For example, a benign glandular
tumor (epithelium tissue) is called adenoma and a benign bone
tumor is called osteoma while a malignant glandular tumor
is called adenocarcinoma and a malignant bone tumor is called
osteosarcoma.
In addition to benign tumors, there are in
situ tumors and invasive
tumors. (Get 
Acrobat
Reader to view and print the in situ and invasive
graphics.) In situ tumors do not invade the basement membrane,
whereas invasive tumors do invade the basement membrane.
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