Types of Breast Cancer
It is important to understand some of the key words used to describe
different types of breast cancer. It is not unusual for a single
breast tumor to be a combination of these types and to have a mixture
of invasive and in situ cancer.
Adenocarcinoma
Nearly all breast cancers start in the ducts or lobules
of the breast. Because this is glandular tissue, they are called
adenocarcinomas, a term applied to cancers of glandular tissue anywhere
in the body. The 2 main types of breast adenocarcinomas are ductal
carcinomas and lobular carcinomas.
In situ
This term is used for the early stage of cancer, when
it is confined to the immediate area where it began. Specifically
in breast cancer, in situ means that the cancer remains confined
to ducts (ductal carcinoma in situ) or lobules (lobular carcinoma
in situ). It has not invaded surrounding fatty tissues in the breast
nor spread to other organs in the body.
Ductal carcinoma in situ (DCIS)
Ductal carcinoma in situ (also known as intraductal carcinoma) is
the most common type of noninvasive breast cancer. DCIS means that
the cancer cells are inside the ducts but have not spread through
the walls of the ducts into the surrounding breast tissue.
About 20% of new breast cancer cases will be DCIS. Nearly all women
diagnosed at this early stage of breast cancer can be cured. A mammogram
is the best way to find DCIS early.
When DCIS is diagnosed, the pathologist (a doctor specializing
in diagnosing disease from tissue samples) will consider whether
an area of dead or degenerating cancer cells, called tumor necrosis,
is present. If necrosis is present, the tumor is considered more
aggressive. The term comedocarcinoma is often used to describe DCIS
with necrosis.
Lobular carcinoma in situ (LCIS)
Although not a true cancer, LCIS (also called lobular neoplasia)
is sometimes classified as a type of noninvasive breast cancer,
and this is why it is included here. It begins in the milk-producing
glands but does not grow through the wall of the lobules.
Most breast cancer specialists think that LCIS itself does not
usually become an invasive cancer, but women with this condition
do have a higher risk of developing an invasive breast cancer in
the same breast or in the opposite breast. For this reason, women
with LCIS, in particular, should pay close attention to having regular
mammograms (see below for guidelines).
Infiltrating (or invasive) ductal carcinoma (IDC)
This is the most common breast cancer. It starts in a milk passage,
or duct, of the breast, has broken through the wall of the duct,
and invaded the fatty tissue of the breast. At this point, it can
metastasize, or spread to other parts of the body through the lymphatic
system and bloodstream. About 80% of invasive breast cancers are
infiltrating ductal carcinomas.
Infiltrating (or invasive) lobular carcinoma (ILC)
Infiltrating lobular carcinoma starts in the milk-producing glands,
or lobules. Similar to IDC, it also can spread (metastasize) to
other parts of the body. About 10% of invasive breast cancers are
ILCs. Invasive lobular carcinoma may be harder to detect by a mammogram
than invasive ductal carcinoma.
Inflammatory breast cancer
This uncommon type of invasive breast cancer accounts for about
1% to 3% of all breast cancers. It makes the skin of the breast
look red and feel warm and gives the skin a thick, pitted appearance.
Doctors now know that these changes are not caused by inflammation
or infection, but by cancer cells blocking lymph vessels or channels
in the skin.
Medullary carcinoma
This special type of infiltrating breast cancer has a rather well-defined,
distinct boundary between tumor tissue and normal tissue. It also
has some other special features, including the large size of the
cancer cells and the presence of immune system cells at the edges
of the tumor. Medullary carcinoma accounts for about 5% of breast
cancers. The outlook, or prognosis, for this kind of breast cancer
is better than for other types of invasive breast cancer. But these
are often hard to distinguish from infiltrating ductal carcinoma
and are treated the same way.
Mucinous carcinoma
This rare type of invasive breast cancer is formed by mucus-producing
cancer cells. The prognosis for mucinous carcinoma is better than
for the more common types of invasive breast cancer. Colloid carcinoma
is another name for this type of breast cancer.
Paget disease of the nipple
This type of breast cancer starts in the breast ducts and spreads
to the skin of the nipple and then to the areola, the dark circle
around the nipple. It is rare, accounting for only 1% of all cases
of breast cancer. The skin of the nipple and areola often appears
crusted, scaly, and red, with areas of bleeding or oozing. The woman
may notice burning or itching. Paget disease may be associated with
in situ carcinoma or with infiltrating breast carcinoma. If no lump
can be felt in the breast tissue and the biopsy shows DCIS but no
invasive cancer, the prognosis is excellent.
Phyllodes tumor
This very rare breast tumor develops in the stroma (connective tissue)
of the breast, in contrast to carcinomas, which develop in the ducts
or lobules. Phyllodes (also spelled phylloides) tumors are usually
benign but on rare occasions may be malignant.
Benign phyllodes tumors are treated by removing the mass and a
narrow margin of normal breast tissue. A malignant phyllodes tumor
is treated by removing it along with a wider margin of normal tissue,
or by mastectomy. These cancers do not respond to the usual treatments
for invasive ductal or lobular breast cancer. In the past, both
benign and malignant phyllodes tumors were referred to as cystosarcoma
phyllodes.
Tubular carcinoma
Tubular carcinomas are another special type of infiltrating breast
carcinoma. It was named tubular because of the way the cells look
under the microscope. Tubular carcinomas account for about 2% of
all breast cancers and have a better prognosis than infiltrating
ductal or lobular carcinomas.
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