Not all breast cancers are the same. Breast cancers are categorized based on the type of tissue where the cancer begins.
The area where breast cancer begins determines how the disease typically behaves. This information helps doctors decide which treatments will be most effective.
The following are common forms of breast cancer:
Ductal Carcinoma in Situ (DCIS)
Ductal carcinoma in situ, or DCIS, is also known as intraductal carcinoma.
DCIS begins in the cells of the milk ducts, but it can turn into a more invasive form of cancer.
About one in five new breast cancer cases is DCIS, according to the American Cancer Society.
DCIS is very treatable unless it's left untreated or undetected, in which case it can spread to other areas.
Invasive Ductal Carcinoma (IDC)
The most common type of breast cancer, invasive ductal carcinoma (IDC or infiltrative breast cancer), accounts for about 70 to 80 percent of all breast cancer diagnoses, according to the National Breast Cancer Foundation.
IDC is also the type of breast cancer that most commonly affects men.
Like DCIS, invasive ductal carcinoma starts in the milk duct of the breast. But unlike DCIS, it spreads beyond the wall of the duct and into the fatty tissue of the breast.
From this point, the cancer may spread (metastasize) to other parts of the body through the lymphatic system and bloodstream.
Invasive Lobular Carcinoma (ILC)
Originating in the milk-producing glands, known as lobules, invasive lobular carcinoma (ILC) can spread to other parts of the body, just like IDC.
According to the American Cancer Society, about 1 in 10 invasive breast cancers is ILC.
This form of breast cancer is often harder to detect by mammogram than IDC is.
Inflammatory Breast Cancer (IBC)
Inflammatory breast cancer (IBC) accounts for only 1 to 3 percent of all breast cancers, according to the American Cancer Society.
However, it's a very aggressive form of cancer. IBC has a higher chance of spreading and a worse outlook than other breast cancers.
Sometimes in its early stages, IBC is mistaken for an infection in the breast (called mastitis) and treated with antibiotics, which won't help the condition.
Unlike other types of breast cancer, IBC usually doesn't cause a lump or tumor, which can make it hard to detect with a mammogram.
Instead, because the cancer cells block lymph vessels in the skin, IBC may cause the following:
- Skin on the breast that is red and feels warm
- A thick, pitted surface of the breast, somewhat like an orange peel
- A larger, firmer, tender, or itchy breast
Paget Disease of the Breast
Also known as Paget's disease of the nipple or mammary Paget disease, this type of cancer starts in the breast ducts and spreads to the skin of the nipple, then to the areola (dark circle around the nipple).
Paget disease is frequently misdiagnosed at first, because the first noticeable symptoms can easily be confused with more common skin conditions affecting the nipple.
Paget disease of the breast may cause the following symptoms:
- Crusted, scaly, or red skin of the nipple and areola
- Bleeding or oozing in the breasts
- Burning or itching sensations in the area
According to the American Cancer Society, Paget disease is present in only about 1 percent of all breast cancer cases, but is almost always associated with either DCIS or IDC.
When Paget disease appears on the nipple, one or more tumors are most likely present inside the same breast. A mastectomy (removal of the breast and breast tissue) is often required.
If no lump can be felt in the breast tissue, and a biopsy shows DCIS but no invasive cancer, the outlook is good.
However, if invasive cancer is present, the cancer will need to be treated more aggressively.
Triple Negative Breast Cancer
A triple negative breast cancer diagnosis means that the breast cancer cells you carry have tested negative for the three most common types of receptors that cause most breast cancer growth.
These receptors are human epidermal growth factor receptor 2 (HER-2), estrogen receptors (ER), and progesterone receptors (PR).
Common breast cancer treatments — like hormone therapy or drugs that target estrogen, progesterone, and HER-2 — are ineffective against triple negative breast cancer.
However, chemotherapy, immunotherapy, and targeted therapies are still effective options, and the cancer may respond even better to chemotherapy in the earlier stages than many other forms of cancer do.
Other Forms of Breast Cancer
The following types of breast cancer can also occur:
Medullary carcinoma accounts for 3 to 5 percent of all breast cancer cases, according to the National Breast Cancer Foundation.
In most cases, a tumor cannot be felt, but a spongy change of breast tissue may be noticeable. A mammogram can detect this form of cancer.
Tubular carcinoma is a collection of cells that can feel like a spongy area of breast tissue rather than a lump.
It's usually found in women age 50 and above and accounts for 2 percent of all breast cancer diagnoses, according to the National Breast Cancer Foundation.
A mammogram usually detects this cancer, and hormone therapy can be an effective treatment.
Mucinous carcinoma (or mucinous colloid) is characterized by mucus production and cells that are poorly defined.
It accounts for about 1 to 2 percent of all breast cancers, and most often has a good outlook.