All organs in the body are made of cells. Individual cells are so
small, they can be seen only through a microscope. Normally, cells
divide in an orderly fashion to replace cells that have aged and died.
Controls within each cell tell it to stop dividing if no new cells
Occasionally, damage to DNA during cell duplication may cause the
controls to malfunction. Cells begin to divide uncontrollably, forming
lumps or tumors.
The word "tumor" comes from a Latin word that means "swelling."
A tumor could be composed of cells that divide excessively, but that
do not invade or damage other parts of the body. A good example is
a fibroid in the uterus, or a fibroadenoma in the breast. Both of
these are called benign, that is, non-cancerous tumors.
Malignant tumors are composed of aggressively dividing cells that
destroy surrounding tissues or travel to other parts of the body.
In general conversation, the word "tumor" is often used
to refer to a malignant condition, or cancer.
Growth rate is the speed at which a lump or tumor grows. Different
types of breast cancer grow at different rates. The time it takes
for a tumor to become twice as large is called doubling time. The
average doubling time for most breast cancer tumors is in the range
of 50 to 200 days.
The change of the first normal cell into a malignant cell happens
years before any evidence of cancer can be detected by any tests that
we have today. It may take three to five years for a cluster of cancerous
cells to become large enough to be seen on a mammogram. In other words,
by the time your cancer has been detected, it has been there for several
years. That is why there is no harm in taking a few more weeks to
decide on the best treatment possible.
of Breast Cancer
Breast cancer types are named according to the part of the breast
in which they develop. The most common forms of breast cancer come
from cells that line the milk ducts (ductal cancer) or the milk-producing
lobules (lobular cancer).
In the early stages, cancer cells divide locally, and do not cross
the wall of the duct or lobule. This type of cancer is called in situ (meaning
"in place"). Once the cancer cells cross the lining of the duct
or lobule, they are called infiltrating, or invasive. Do not be unduly
alarmed if you are told your cancer is "invasive." Most
cancers are, so your invasive cancer is the "normal" cancer.
Today about one in five cases of diagnosed breast cancers fall into
the non-invasive, or in situ category—either ductal carcinoma
in situ (DCIS), or lobular carcinoma in situ (LCIS).
DCIS cancers are highly curable. Some physicians don't even refer
to them as cancer, but rather as "precancerous lesions,"
since DCIS may never progress to be an invasive cancer. The treatment
of DCIS may not follow the same plan as for invasive cancers, so we
have dedicated a separate chapter to this non-invasive form of the
disease. You still need to read the chapters on staging, surgery and
radiation to understand the principles involved.
LCIS is a non-invasive growth that is not considered cancerous, but
women who are diagnosed with LCIS have about a 1% per year risk of
developing invasive breast cancer. That means that twenty years after
diagnosis, the risk is about 18%. What is important to know is that
the invasive cancer can occur in either breast, and not necessarily
where the LCIS was originally found. In other words, LCIS is not a
precursor, but a marker. Infiltrating or invasive cancers, where malignant
cells cross the lining of the duct or lobule, are more advanced than
in situ cancers. They invade, or infiltrate, adjacent tissues. The
most common type of breast cancer is the infiltrating ductal carcinoma.
More than half of all cases are of this type.
Other types of breast cancer are less common. One example
is Paget's Disease, a cancerous growth that first appears as scaling
on the nipple, and may be confused for a simple rash. Another is inflammatory
cancer, a rare form of cancer that grows quickly, causing redness
and swelling of the breast. This is really the only form of breast
cancer in which the treatment decision needs to be made as soon as
How Cancer Spreads
As a malignant tumor grows, it may spread locally, invading and sometimes
destroying other tissues, or cells may break away from the tumor and
get into the lymphatic vessels, or into the blood vessels, and travel
to distant parts of the body. Some of the breakaway cells will be
trapped in the lymph nodes of the armpit, or axilla. Examination of
these nodes by a procedure called axillary lymph node dissection,
can help determine the stage (the degree of spread) of the cancer.
If cancer cells escape beyond the lymph nodes, or enter
the circulatory system directly, they can spread to the liver, brain,
lungs, and bones, forming new tumors called metastases. These distant
metastases are the most worrisome, because they can damage vital organs.
This advanced stage of breast cancer, called metastatic cancer, is
less common and its management is more difficult.
To make sure that no cancer cells remain anywhere in
the body, it is often necessary to use systemic therapy—therapy
that reaches all the organs, in all parts of the body, by means of
the blood stream. This is explained in the Chemotherapy and Hormone
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