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Your breast is made up of lobules and ducts surrounded by fatty and connective tissue. The glandular lobules produce milk which is transported to the nipple through the ducts.
Breast cancer occurs when normal cells in the lobules, ducts, or other breast tissue become damaged and grow out of control. The abnormal cells rapidly grow and accumulate, forming a mass called a tumor.
If a tumor grows but doesn’t spread into nearby breast tissue, it’s called benign and is not considered cancer. A malignant tumor spreads, invading surrounding tissue and is considered cancerous.
Because it can start in lobules, ducts, or other tissue, there are many different types of breast cancer.
Breast cancer can be categorized in several ways. Most often it’s classified by where it originates and whether it moves from that spot.
An easily identifiable characteristic of breast cancer is the type of cell it’s formed in.
- Ductal carcinoma is formed in the cells lining the milk ducts.
- Lobular carcinoma is formed in the milk-producing lobules.
Another important characteristic of breast cancer is whether it invades surrounding tissue or stays where it originally formed.
- Noninvasive (in situ) breast cancer has not spread into surrounding tissue.
- Invasive (infiltrating) breast cancer has moved into the tissue surrounding it.
Combining these classifications gives a descriptive name to the type of breast cancer as outlined below.
- Ductal carcinoma in situ is a tumor that formed in ductal cells and has not spread to nearby tissue.
- Invasive ductal carcinoma is a tumor that formed in ductal cells and then spread to nearby tissue.
- Lobular carcinoma in situ is a tumor that formed in lobular cells and has not spread to nearby tissue.
- Invasive lobular carcinoma is a tumor that formed in lobular cells and then spread to nearby tissue.
The symptoms of breast cancer can vary widely and some types of breast cancer may not have any noticeable symptoms.
Sometimes a lump may be too small to be felt or to cause any changes to your breast or surrounding area. In these cases, cancerous cells are often first detected through screening techniques like a mammogram.
When there are symptoms, they can include:
- a lump or thickening of breast tissue that you can feel with your fingers
- breast swelling or changes to your breast size or shape
- changes to the skin on your breast, such as dimpling, redness, or skin irritation
- the nipple turning inward or nipple pain
- a lump in your underarm area
- nipple discharge other than breast milk
It’s important to be familiar with how your breasts usually look and feel. This will help you notice any changes and to follow up with your healthcare professional promptly if anything looks or feels different.
Noninvasive breast cancer develops in the cells of a duct or lobule and remains in that location. It’s also referred to as “in situ” which means “in the original place”.
There are two types of noninvasive breast cancer:
- ductal carcinoma in situ (DCIS)
- lobular carcinoma in situ (LCIS)
Let’s take a closer look at each type.
Ductal carcinoma in situ
- forms in the cells lining a milk duct
- remains in the duct and does not spread to nearby tissues
- is considered “precancer” or “preinvasive” because, if left untreated, it can become invasive and spread into nearby tissue
- accounts for about
15 to 20 percentof all breast cancers
- usually only occurs in one breast
If the cancer is hormone receptor positive, it may be treated with tamoxifen or an aromatase inhibitor (for postmenopausal patients) for 5 years after surgery. This treatment is thought to lower the risk of DCIS recurrence or invasive cancer developing in either breast.
Lobular carcinoma in situ
- forms in the cells lining a lobule
- remains in the lobule and does not spread to nearby tissues
- is usually considered a change in the breast rather than cancer
- is thought to be a marker of increased risk of developing invasive cancer
- tends to develop in both breasts
- is more prevalent in premenopausal women
Treatment for LCIS requires close follow-up with your doctor due to the high risk of developing invasive breast cancer. Your LCIS may need no treatment, or your doctor may recommend it be removed with breast-conserving surgery like an excisional biopsy.
Invasive breast cancer also develops in the cells of a duct or lobule, but it doesn’t remain where it originated. Instead, it spreads and invades surrounding tissue. Another name for it is “infiltrating.”
There are two types of invasive breast cancer:
- invasive (infiltrating) ductal carcinoma (IDC)
- invasive (infiltrating) lobular carcinoma (ILC)
Invasive ductal carcinoma
- forms in the cells lining a milk duct
- spreads into nearby tissue
- is the most common type of breast cancer, accounting for about
70 to 80 percentof all breast cancers
- is the most common type of breast cancer found in men
Breast cancer is typically further classified based on the surface proteins that are found on the cancer cells.
When breast cancer tissue is removed from your body, it’s tested for these proteins. The cancer cells are then subtyped based on the presence or absence of surface proteins. Knowing the subtype can help your doctor determine the best course of treatment for your cancer.
Let’s look at the three most common subtypes for breast cancer.
Hormone receptor positive
This subtype has estrogen and/or progesterone receptors. An “ER positive” tumor has estrogen receptors, while a “PR positive” tumor has progesterone receptors. This subtype often needs the hormones corresponding to its receptors to grow.
Treatment with anti-estrogen or anti-progesterone hormone therapy can block tumor growth and kill the cancer cells. If there are no receptors, it’s called a “hormone receptor negative” tumor.
This subtype has extra copies of the HER2 gene, so it produces too much of a growth hormone called HER2. This hormone allows the cancer to grow more quickly.
Treatment typically involves medications that can slow the production of this hormone and kill the cancer cells.
Cancers that do not have ER, PR, or HER2 receptors, are called “triple negative”.
It’s more common in women who have a BRCA1 gene mutation, so your doctor my recommend you be tested for this mutation if your cancer is triple negative.
Less common types of breast cancer are often named by the way they look under a microscope. Here’s a closer look at several less common types.
Inflammatory breast cancer (IBC)
Inflammatory breast cancer accounts for about
Some of the most common symptoms of IBC include:
- a swollen, warm, red breast
- breast skin that’s thickened or pitted
- a breast that feels larger or heavier than normal
- pain or tenderness in the breast or surrounding area
- itchiness on or around the breast
- an inverted nipple
The symptoms of IBC are caused by a blockage of the lymphatic system within the breast. These symptoms tend to develop quickly, usually within 3 to 6 months.
Paget disease of the breast
Paget disease is a rare cancer that forms in the milk ducts and spreads to the skin of the nipple and areola, the skin around the nipple. According to the
The symptoms of Paget disease are often mistaken at first for skin conditions, like eczema or dermatitis. However, the symptoms won’t respond to topical treatments.
The typical symptoms of Paget disease include:
- redness, flaking or crusting around the nipple and areola
- a tingling or itching sensation around the nipple area
- thickened skin on or near the nipple
- a flattened nipple
- bloody or yellowish discharge from the nipple
Phyllodes tumors of the breast
Phyllodes tumors form in the connective tissue of the breast. The most common symptoms include:
- a smooth lump in or around the breast
- a lump that grows quickly and stretches the skin
- breast skin that looks red and feels warm
Tubular carcinoma of the breast
Tubular carcinoma is a subtype of invasive ductal carcinoma (IDC). This type of breast cancer gets its name due to the tube-shaped structures, which can be seen under a microscope, that make up the tumor. The tumors are usually small (about 1 centimeter or less) and tend to grow slowly.
Tubular carcinoma is rare, accounting for up to
Because these tumors are small, they are most often detected during a routine mammogram. They tend to be low grade with good prognosis.
Mucinous (colloid) carcinoma of the breast
Mucinous carcinoma, also known as colloid carcinoma, is a rare form of invasive ductal carcinoma (IDC). About 2 percent of breast cancers are “pure” mucinous carcinoma, while up to 7 percent of breast cancers have some component of mucinous carcinoma cells.
With this type of cancer, the tumor consists of abnormal cells that appear to “float” in pools of mucus when looked at under a microscope.
It’s typically a less aggressive type of cancer that has a lower probability of spreading to the axillary (underarm) lymph nodes than some other types of IDC.
Mucinous carcinoma tends to be more common in post-menopausal women, with the average age at diagnosis being around 60 to 70 years of age.
Medullary carcinoma of the breast
Medullary carcinoma of the breast is another rare subtype of invasive ductal carcinoma (IDC). It accounts for around
The tumor is typically a soft, fleshy mass rather than a lump in the breast tissue. The mass most often develops in the middle of the breast and is most often found in women with the BRCA1 mutation.
Although these cancer cells often have an aggressive appearance, they don’t grow quickly and usually don’t spread to the lymph nodes. This makes it easier to treat than some other types of breast cancer.
The treatment of breast cancer varies depending on many factors, such as:
- the cancer stage
- how far it has spread
- tumor size
- whether it is hormone receptor and HER2 positive or triple negative
- other underlying health conditions
- the patient’s preference
Possible treatment options for breast cancer include:
- Lumpectomy. This breast-conserving surgery is usually used for smaller, less invasive tumors. It involves only removing the tumor and some surrounding tissue.
- Mastectomy. With a mastectomy, the entire breast is removed. The type of mastectomy can differ depending on how invasive the cancer is.
- Radiation therapy. Radiation therapy is often used to destroy any cancer cells remaining in the breast or surrounding tissue after surgical removal of the cancer.
- Chemotherapy. Chemotherapy medication is often used to destroy cancer cells that have spread to distance parts of the body.
- Hormone therapy. Anti-estrogen and anti-progesterone therapy can be used to slow the growth of hormone receptor-positive tumors.
- Immunotherapy. Immunotherapy is a way to stimulate your immune system so that it’s able to recognize and attack cancer cells. This is a growing area of research that’s continuing to find new ways to treat cancer.
- Other targeted therapy. For HER2-positive breast cancer, some types of targeted therapy can detect and disrupt the growth-promoting proteins on the surface of the cancer cells. This may help slow the growth of HER2-positive tumors.
Regular breast self-examinations, and mammograms help detect breast cancer in its early stages. Finding breast cancer that has not yet spread gives you the best chance of remaining healthy and cancer-free for many years.
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Other steps you can take to lower your risk of getting breast cancer include the following:
- Limit alcohol to no more than one drink a day.
- Maintain a moderate weight throughout your life.
- Stay physically active.
- Breastfeed if you can.
- Avoid hormone therapy for postmenopausal symptoms.
- Avoid breast implants.
- Talk to your doctor about medication or surgical treatments to reduce the chances you will get breast cancer if you are at high risk.
There are many types of breast cancer. Some types of breast cancer develop in the milk-producing lobules in your breast while others grow in the cells lining the milk ducts. Some tumors are benign and noninvasive, but others can be malignant, invading nearby breast tissue.
Breast cancer can be treated with surgery, chemotherapy, radiation therapy, targeted medication, and hormone therapy. However, you’ll need less treatment if breast cancer is detected early through breast self-examinations or routine mammograms.