Breast cancer usually first spreads to the lymph nodes under the arms, around the collarbone and inside the breasts. The lymph nodes where cancer is likely to first spread are known as sentinel nodes. Other parts of the body to which breast cancer commonly spreads are bones, brain, lungs and liver.
Lymph nodes are small bean-shaped glands found all over the body, a part of the immune system that helps trap bacteria and drain metabolic waste. Lymphatic fluid circulates through ducts that connect the lymph nodes and cancer cells can spread to other organs easily through the lymphatic ducts. Breast cancer can also spread through blood circulation.
What is breast cancer?
Breast cancer is cancer (abnormal cells that grow out of control) that starts in the breast tissues. Breast cancer is one of the most common cancers that affect women and is the second leading cause of cancer deaths in women. Men can also develop breast cancer, however, less than 1% of breast cancers are diagnosed in men.
Cancers are a unique group of diseases caused by genetic mutations, which make certain types of cells turn abnormal and grow out of control. Most types of cancers grow into masses of tissue known as tumors. Cancer spreads when tumor cells break off from the primary tumor, migrate to other parts of the body and start growing.
What are the types of breast cancer?
Breast cancers are classified by the types of cells in which they develop, and whether they are invasive or noninvasive. Invasive cancers grow into nearby tissue while noninvasive tumors are slow-growing and remain localized.
Breast cancers are also grouped by the presence of mutations in certain genes such as HER2 and BRCA1 and whether they grow in response to estrogen and progesterone, the female hormones. Breast cancers that grow in response to hormones have proteins known as hormone receptors (HR) on them.
Breasts consist of milk glands and ducts, connective and fat tissue. Most breast cancers start in the milk-producing glands (lobules) and ducts in the breast. The types of breast cancers include:
Noninvasive or preinvasive breast cancers
Noninvasive cancers remain confined to the primary site of development, but are always treated, because it is not possible to know if they will become invasive or not. Noninvasive breast cancers include:
- Ductal carcinoma in situ (DCIS): Abnormal cells in the milk duct
- Lobular carcinoma in situ (LCIS): Abnormal cells in the lobules
Invasive breast cancers
Invasive or infiltrating cancers are those that spread into nearby breast tissue. The two main types of invasive breast cancers are:
- Invasive ductal carcinoma (IDC): IDC starts in the milk ducts and accounts for 80% of invasive breast cancers.
- Invasive lobular carcinoma (ILC): ILC starts in the lobules and accounts for 10% of invasive breast cancers.
Less common types of breast cancers include:
- Inflammatory breast cancer: A type of breast cancer with inflammatory symptoms such as swelling and redness caused by cancer cells blocking the lymphatic ducts.
- Breast angiosarcoma: Cancer that starts in the cells which line the blood or lymph vessels in the breast.
- Paget’s disease: Cancer that starts in the ducts and spreads to the nipple and areola, the dark skin around the nipple.
- Phyllodes tumor: Tumor that develops in the connective tissue in the breast. Approximately 75% of phyllodes tumors are benign.
Rare subtypes of invasive ductal carcinomas that are less aggressive and less likely to spread include:
- Adenoid Cystic carcinoma
- Low grade adenosquamous carcinoma
- Medullary carcinoma
- Mucinous carcinoma
- Papillary carcinoma
- Tubular carcinoma
Rare subtypes of invasive ductal carcinoma that are aggressive and spread fast include the following:
- Metaplastic carcinoma
- Micropapillary carcinoma
- Mixed carcinoma with features of both ductal and lobular carcinomas
What are the stages of breast cancer?
Breast cancers are staged by the size of the tumor and extent of spread. Breast cancers are also graded from one to three, based on how abnormal the cancer cells look and how fast they grow. One is low grade and three is a high grade cancer that is more likely to grow rapidly and spread. In addition, breast cancer may be staged as noted below.
The four stages of breast cancer are:
- Stage I: The tumor is relatively small and localized to the original site with possible spread to the sentinel lymph nodes.
- Stage II: The tumor has grown and spread to a few nearby lymph nodes.
- Stage III: The tumor has grown into many lymph nodes and other tissue in the breast.
- Stage IV: The cancer has spread (metastatic cancer) to distant parts of the body such as bone, brain, lungs or liver.
Other staging systems state there are 5 stages with Stage 0 representing non-invasive cancer cells. Another classification that is highly detailed is the TNM system, based on tumor size, lymph node involvement and metastatic spread.
What are the signs that breast cancer has spread?
General symptoms that breast cancer has spread include the following:
Other symptoms depend on where the cancer has spread and can include:
What are the survival rates for breast cancer?
The survival rates for breast cancers are excellent if the cancer is detected and treated early. The five-year survival rates for breast cancers are:
|Localized||The cancer is confined to the site of origin||99%|
|Regional||The cancer has spread to nearby tissues and/or lymph nodes||86%|
|Distant||The cancer has spread to distant parts of the body||28%|
The above survival rates are based only on the stage of cancer at the time of diagnosis. Survival with breast cancer also depends on many other factors such as the age and overall health of the patient, type and grade of cancer, presence and type of gene mutations, hormone receptor status and response to treatment. Each patient is unique; survival rates are averages.
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