What is breast cancer in woman?
Breast cancer is a malignant tumor that starts in the cells of the
breast. A malignant tumor is a group of cancer cells that can grow into
(invade) surrounding tissues or spread (metastasize) to distant areas of
the body. The disease occurs almost entirely in women, but men can get
it, too.
The normal breast
To understand breast cancer, it helps to have some basic knowledge
about the normal structure of the breasts, shown in the diagram below.
The female breast is made up mainly of lobules (milk-producing glands), ducts (tiny tubes that carry the milk from the lobules to the nipple), and stroma (fatty tissue and connective tissue surrounding the ducts and lobules, blood vessels, and lymphatic vessels).
Most breast cancers begin in the cells that line the ducts (ductal cancers). Some begin in the cells that line the lobules (lobular cancers), while a small number start in other tissues.
The lymph (lymphatic) system of the breast
The lymph system is important to understand because it is one way breast cancers can spread. This system has several parts.
Lymph nodes are small, bean-shaped collections of immune system cells
(cells that are important in fighting infections) that are connected by
lymphatic vessels. Lymphatic vessels are like small veins, except that
they carry a clear fluid called lymph (instead of blood) away
from the breast. Lymph contains tissue fluid and waste products, as well
as immune system cells. Breast cancer cells can enter lymphatic vessels
and begin to grow in lymph nodes.
Most lymphatic vessels in the breast connect to lymph nodes under the arm (axillary nodes). Some lymphatic vessels connect to lymph nodes inside the chest (internal mammary nodes) and those either above or below the collarbone (supraclavicular or infraclavicular nodes).
If the cancer cells have spread to lymph nodes, there is a higher
chance that the cells could have also gotten into the bloodstream and
spread (metastasized) to other sites in the body. The more lymph nodes
that have breast cancer, the more likely it is that the cancer may be
found in other organs as well. Because of this, finding cancer in one or
more lymph nodes often affects the treatment plan. Still, not all women
with cancer cells in their lymph nodes develop metastases, and some
women can have no cancer cells in their lymph nodes and later develop
metastases.
Benign breast lumps
Most breast lumps are not cancerous (benign). Still, some may need to
be sampled and viewed under a microscope to prove they are not cancer.
Fibrocystic changes
Most lumps turn out to be fibrocystic changes. The term fibrocystic
refers to fibrosis and cysts. Fibrosis is the formation of scar-like
(fibrous) tissue, and cysts are fluid-filled sacs. Fibrocystic changes
can cause breast swelling and pain. This often happens just before a
woman's menstrual period is about to begin. Her breasts may feel lumpy
and, sometimes, she may notice a clear or slightly cloudy nipple
discharge.
Other benign breast lumps
Benign breast tumors such as fibroadenomas or intraductal papillomas
are abnormal growths, but they are not cancerous and do not spread
outside the breast to other organs. They are not life threatening.
Still, some benign breast conditions are important because women with
these conditions have a higher risk of developing breast cancer.
Invasive (infiltrating) carcinoma
An invasive cancer is one that has already grown beyond the layer of
cells where it started (as opposed to carcinoma in situ). Most breast
cancers are invasive carcinomas — either invasive ductal carcinoma or
invasive lobular carcinoma.
Sarcoma
Sarcomas are cancers that start in connective tissues such as muscle
tissue, fat tissue, or blood vessels. Sarcomas of the breast are rare.
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