There are several types of breast cancer, but some of them are quite
rare. In some cases a single breast tumor can be a combination of these
types or be a mixture of invasive and in situ cancer.
Ductal carcinoma in situ
Ductal carcinoma in situ (DCIS; also known as intraductal carcinoma)
is the most common type of non-invasive 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 1 in 5 new breast cancer cases will be DCIS. Nearly all women
diagnosed at this early stage of breast cancer can be cured. A mammogram
is often the best way to find DCIS early.
When DCIS is diagnosed, the pathologist (a doctor specializing in
diagnosing disease from tissue samples) will look for areas of dead or
dying cancer cells, called tumor necrosis, within the tissue sample. If necrosis is present, the tumor is likely to be more aggressive. The term comedocarcinoma is often used to describe DCIS with necrosis.
Lobular carcinoma in situ
This is not a true cancer or pre-cancer
Invasive (or infiltrating) ductal carcinoma
This is the most common type of breast cancer. Invasive (or
infiltrating) ductal carcinoma (IDC) starts in a milk passage (duct) of
the breast, breaks through the wall of the duct, and grows into the
fatty tissue of the breast. At this point, it may be able to spread
(metastasize) to other parts of the body through the lymphatic system
and bloodstream. About 8 of 10 invasive breast cancers are infiltrating
ductal carcinomas.
Invasive (or infiltrating) lobular carcinoma
Invasive lobular carcinoma (ILC) starts in the milk-producing glands
(lobules). Like IDC, it can spread (metastasize) to other parts of the
body. About 1 in 10 invasive breast cancers is an ILC. Invasive lobular
carcinoma may be harder to detect by a mammogram than invasive ductal
carcinoma.
Less common types of breast cancer
Inflammatory breast cancer: This uncommon type of invasive
breast cancer accounts for about 1% to 3% of all breast cancers. Usually
there is no single lump or tumor. Instead, inflammatory breast cancer
(IBC) makes the skin of the breast look red and feel warm. It also may
give the breast skin a thick, pitted appearance that looks a lot like an
orange peel. Doctors now know that these changes are not caused by
inflammation or infection, but by cancer cells blocking lymph vessels in
the skin. The affected breast may become larger or firmer, tender, or
itchy. In its early stages, inflammatory breast cancer is often mistaken
for an infection in the breast (called mastitis). Often this
cancer is first treated as an infection with antibiotics. If the
symptoms are caused by cancer, they will not improve, and a biopsy will
find cancer cells. Because there is no actual lump, it may not show up
on a mammogram, which may make it even harder to find it early. This
type of breast cancer tends to have a higher chance of spreading and a
worse outlook (prognosis) than typical invasive ductal or lobular
cancer.
Triple-negative breast cancer: This term is used to describe
breast cancers (usually invasive ductal carcinomas) whose cells lack
estrogen receptors and progesterone receptors, and do not have an excess
of the HER2 protein on their surfaces. Breast cancers with these characteristics tend to occur more often in
younger women and in African-American women. Triple-negative breast
cancers tend to grow and spread more quickly than most other types of
breast cancer. Because the tumor cells lack these certain receptors,
neither hormone therapy nor drugs that target HER2 are effective
treatments (but chemotherapy can still be useful if needed).
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 about 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 is almost always associated with either ductal
carcinoma in situ (DCIS) or infiltrating ductal carcinoma. Treatment
often requires mastectomy. If no lump can be felt in the breast tissue,
and the biopsy shows DCIS but no invasive cancer, the outlook
(prognosis) is excellent. If invasive cancer is present, the prognosis
is not as good, and the cancer will need to be staged and treated like
any other invasive cancer.
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. Other names for these tumors
include phylloides tumor and cystosarcoma phyllodes. These tumors are usually benign but on rare occasions may be malignant.
Benign phyllodes tumors are treated by removing the tumor along with a
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. Surgery is often all that is needed, but these cancers may
not respond as well to the other treatments used for more common breast
cancers. When a malignant phyllodes tumor has spread, it can be treated
with the chemotherapy given for soft-tissue sarcomas.
Angiosarcoma: This is a form of cancer that starts in cells that
line blood vessels or lymph vessels. It rarely occurs in the breasts.
When it does, it usually develops as a complication of previous
radiation treatments. This is an extremely rare complication of breast
radiation therapy that can develop about 5 to 10 years after radiation.
Angiosarcoma can also occur in the arms of women who develop lymphedema
as a result of lymph node surgery or radiation therapy to treat breast
cancer. These cancers tend to grow and spread quickly. Treatment is generally the same as for other sarcomas.
Special types of invasive breast carcinoma
There are some special types of breast cancer that are sub-types of
invasive carcinoma. These are often named after features seen when they
are viewed under the microscope, like the ways the cells are arranged.
Some of these may have a better prognosis than standard infiltrating ductal carcinoma. These include:
- Adenoid cystic (or adenocystic) carcinoma
- Low grade adenosquamous carcinoma (this is a type of metaplastic carcinoma)
- Medullary carcinoma
- Mucinous (or colloid) carcinoma
- Papillary carcinoma
- Tubular carcinoma
Some sub-types have the same or maybe worse prognosis than standard infiltrating ductal carcinoma. These include:
- Metaplastic carcinoma (most types, including spindle cell and squamous)
- Micropapillary carcinoma
- Mixed carcinoma (has features of both invasive ductal and lobular)
In general, all of these sub-types are still treated like standard infiltrating ductal carcinoma.
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