Breast cancer starts when cells in the
breast begin to grow out of control. These
cells usually form a tumor that can often be
seen on an x-ray or felt as a lump. The
tumor is malignant (cancerous) if the cells
can grow into (invade) surrounding tissues
or spread (metastasize) to distant areas of
the body. Breast cancer occurs almost
entirely in women, but men can get it, too.
Cells in nearly any part of the body can
become cancer, and can spread to other
areas of the body. To learn more about how
all cancers start and spread, see What Is
Cancer?
This information refers only to breast
cancer in women. For information on breast
cancer in men, see Breast Cancer in Men .
Breast cancers can start from different
parts of the breast. Most breast cancers
begin in the ducts that carry milk to the
nipple (ductal cancers). Some start in the
glands that make breast milk (lobular
cancers). There are also other types of
breast cancer that are less common.
A small number of cancers start in other
tissues in the breast. These cancers are
called sarcomas and lymphomas and are not
really thought of as breast cancers.
Although many types of breast cancer can
cause a lump in the breast, not all do. There
are other symptoms of breast cancer you
should watch out for and report to a health
care provider.
It’s also important to understand that most
breast lumps are not cancer, they are
benign. Benign breast tumors are abnormal
growths, but they do not spread outside of
the breast and they are not life threatening.
But some benign breast lumps can increase
a woman's risk of getting breast cancer.
Any breast lump or change needs to be
checked by a health care provider to
determine whether it is benign or cancer,
and whether it might impact your future
cancer risk. For more information see “ What
are the risk factors for breast cancer? ” and
Non-cancerous Breast Conditions .
How Breast Cancer Spreads
Breast cancer can spread through the lymph
system .
The lymph system includes lymph nodes,
lymph vessels and lymph fluid found
throughout the body. Lymph nodes are
small, bean-shaped collections of immune
system cells that are connected by lymph
(or lymphatic) vessels. Lymph 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 lymph vessels and begin to grow
in lymph nodes.
Most of the lymph vessels of the breast
drain into:
Lymph nodes under the arm ( axillary
nodes ) .
Lymph nodes around the collar bone
( supraclavicular and infraclavicular
lymph nodes)
Lymph nodes inside the chest near
the breast bone ( internal mammary
lymph nodes)
If cancer cells have spread to your lymph
nodes, there is a higher chance that the
cells could have spread (metastasized) to
other sites in your body. The more lymph
nodes with breast cancer cells, 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 your treatment plan. Usually,
surgery to remove one or more lymph nodes
will be needed to know whether the cancer
has spread there.
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.
breast begin to grow out of control. These
cells usually form a tumor that can often be
seen on an x-ray or felt as a lump. The
tumor is malignant (cancerous) if the cells
can grow into (invade) surrounding tissues
or spread (metastasize) to distant areas of
the body. Breast cancer occurs almost
entirely in women, but men can get it, too.
Cells in nearly any part of the body can
become cancer, and can spread to other
areas of the body. To learn more about how
all cancers start and spread, see What Is
Cancer?
This information refers only to breast
cancer in women. For information on breast
cancer in men, see Breast Cancer in Men .
Breast cancers can start from different
parts of the breast. Most breast cancers
begin in the ducts that carry milk to the
nipple (ductal cancers). Some start in the
glands that make breast milk (lobular
cancers). There are also other types of
breast cancer that are less common.
A small number of cancers start in other
tissues in the breast. These cancers are
called sarcomas and lymphomas and are not
really thought of as breast cancers.
Although many types of breast cancer can
cause a lump in the breast, not all do. There
are other symptoms of breast cancer you
should watch out for and report to a health
care provider.
It’s also important to understand that most
breast lumps are not cancer, they are
benign. Benign breast tumors are abnormal
growths, but they do not spread outside of
the breast and they are not life threatening.
But some benign breast lumps can increase
a woman's risk of getting breast cancer.
Any breast lump or change needs to be
checked by a health care provider to
determine whether it is benign or cancer,
and whether it might impact your future
cancer risk. For more information see “ What
are the risk factors for breast cancer? ” and
Non-cancerous Breast Conditions .
How Breast Cancer Spreads
Breast cancer can spread through the lymph
system .
The lymph system includes lymph nodes,
lymph vessels and lymph fluid found
throughout the body. Lymph nodes are
small, bean-shaped collections of immune
system cells that are connected by lymph
(or lymphatic) vessels. Lymph 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 lymph vessels and begin to grow
in lymph nodes.
Most of the lymph vessels of the breast
drain into:
Lymph nodes under the arm ( axillary
nodes ) .
Lymph nodes around the collar bone
( supraclavicular and infraclavicular
lymph nodes)
Lymph nodes inside the chest near
the breast bone ( internal mammary
lymph nodes)
If cancer cells have spread to your lymph
nodes, there is a higher chance that the
cells could have spread (metastasized) to
other sites in your body. The more lymph
nodes with breast cancer cells, 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 your treatment plan. Usually,
surgery to remove one or more lymph nodes
will be needed to know whether the cancer
has spread there.
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.
